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[freebsd/src.git] / sys / netinet / tcp_hpts.c

/*-
 * Copyright (c) 2016-2018 Netflix, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_rss.h"

/**
 * Some notes about usage.
 *
 * The tcp_hpts system is designed to provide a high precision timer
 * system for tcp. Its main purpose is to provide a mechanism for
 * pacing packets out onto the wire. It can be used in two ways
 * by a given TCP stack (and those two methods can be used simultaneously).
 *
 * First, and probably the main thing its used by Rack and BBR, it can
 * be used to call tcp_output() of a transport stack at some time in the future.
 * The normal way this is done is that tcp_output() of the stack schedules
 * itself to be called again by calling tcp_hpts_insert(tcpcb, slot). The
 * slot is the time from now that the stack wants to be called but it
 * must be converted to tcp_hpts's notion of slot. This is done with
 * one of the macros HPTS_MS_TO_SLOTS or HPTS_USEC_TO_SLOTS. So a typical
 * call from the tcp_output() routine might look like:
 *
 * tcp_hpts_insert(tp, HPTS_USEC_TO_SLOTS(550));
 *
 * The above would schedule tcp_output() to be called in 550 useconds.
 * Note that if using this mechanism the stack will want to add near
 * its top a check to prevent unwanted calls (from user land or the
 * arrival of incoming ack's). So it would add something like:
 *
 * if (tcp_in_hpts(inp))
 *    return;
 *
 * to prevent output processing until the time alotted has gone by.
 * Of course this is a bare bones example and the stack will probably
 * have more consideration then just the above.
 *
 * In order to run input queued segments from the HPTS context the
 * tcp stack must define an input function for
 * tfb_do_queued_segments(). This function understands
 * how to dequeue a array of packets that were input and
 * knows how to call the correct processing routine.
 *
 * Locking in this is important as well so most likely the
 * stack will need to define the tfb_do_segment_nounlock()
 * splitting tfb_do_segment() into two parts. The main processing
 * part that does not unlock the INP and returns a value of 1 or 0.
 * It returns 0 if all is well and the lock was not released. It
 * returns 1 if we had to destroy the TCB (a reset received etc).
 * The remains of tfb_do_segment() then become just a simple call
 * to the tfb_do_segment_nounlock() function and check the return
 * code and possibly unlock.
 *
 * The stack must also set the flag on the INP that it supports this
 * feature i.e. INP_SUPPORTS_MBUFQ. The LRO code recoginizes
 * this flag as well and will queue packets when it is set.
 * There are other flags as well INP_MBUF_QUEUE_READY and
 * INP_DONT_SACK_QUEUE. The first flag tells the LRO code
 * that we are in the pacer for output so there is no
 * need to wake up the hpts system to get immediate
 * input. The second tells the LRO code that its okay
 * if a SACK arrives you can still defer input and let
 * the current hpts timer run (this is usually set when
 * a rack timer is up so we know SACK's are happening
 * on the connection already and don't want to wakeup yet).
 *
 * There is a common functions within the rack_bbr_common code
 * version i.e. ctf_do_queued_segments(). This function
 * knows how to take the input queue of packets from tp->t_inqueue
 * and process them digging out all the arguments, calling any bpf tap and
 * calling into tfb_do_segment_nounlock(). The common
 * function (ctf_do_queued_segments())  requires that
 * you have defined the tfb_do_segment_nounlock() as
 * described above.
 */

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/hhook.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h>           /* for proc0 declaration */
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/refcount.h>
#include <sys/sched.h>
#include <sys/queue.h>
#include <sys/smp.h>
#include <sys/counter.h>
#include <sys/time.h>
#include <sys/kthread.h>
#include <sys/kern_prefetch.h>

#include <vm/uma.h>
#include <vm/vm.h>

#include <net/route.h>
#include <net/vnet.h>

#ifdef RSS
#include <net/netisr.h>
#include <net/rss_config.h>
#endif

#define TCPSTATES               /* for logging */

#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/in_pcb.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>    /* required for icmp_var.h */
#include <netinet/icmp_var.h>   /* for ICMP_BANDLIM */
#include <netinet/ip_var.h>
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/cc/cc.h>
#include <netinet/tcp_hpts.h>
#include <netinet/tcp_log_buf.h>

#ifdef tcp_offload
#include <netinet/tcp_offload.h>
#endif

/*
 * The hpts uses a 102400 wheel. The wheel
 * defines the time in 10 usec increments (102400 x 10).
 * This gives a range of 10usec - 1024ms to place
 * an entry within. If the user requests more than
 * 1.024 second, a remaineder is attached and the hpts
 * when seeing the remainder will re-insert the
 * inpcb forward in time from where it is until
 * the remainder is zero.
 */

#define NUM_OF_HPTSI_SLOTS 102400

/* Each hpts has its own p_mtx which is used for locking */
#define HPTS_MTX_ASSERT(hpts)   mtx_assert(&(hpts)->p_mtx, MA_OWNED)
#define HPTS_LOCK(hpts)         mtx_lock(&(hpts)->p_mtx)
#define HPTS_TRYLOCK(hpts)      mtx_trylock(&(hpts)->p_mtx)
#define HPTS_UNLOCK(hpts)       mtx_unlock(&(hpts)->p_mtx)
struct tcp_hpts_entry {
        /* Cache line 0x00 */
        struct mtx p_mtx;       /* Mutex for hpts */
        struct timeval p_mysleep;       /* Our min sleep time */
        uint64_t syscall_cnt;
        uint64_t sleeping;      /* What the actual sleep was (if sleeping) */
        uint16_t p_hpts_active; /* Flag that says hpts is awake  */
        uint8_t p_wheel_complete; /* have we completed the wheel arc walk? */
        uint32_t p_curtick;     /* Tick in 10 us the hpts is going to */
        uint32_t p_runningslot; /* Current tick we are at if we are running */
        uint32_t p_prev_slot;   /* Previous slot we were on */
        uint32_t p_cur_slot;    /* Current slot in wheel hpts is draining */
        uint32_t p_nxt_slot;    /* The next slot outside the current range of
                                 * slots that the hpts is running on. */
        int32_t p_on_queue_cnt; /* Count on queue in this hpts */
        uint32_t p_lasttick;    /* Last tick before the current one */
        uint8_t p_direct_wake :1, /* boolean */
                p_on_min_sleep:1, /* boolean */
                p_hpts_wake_scheduled:1, /* boolean */
                hit_callout_thresh:1,
                p_avail:4;
        uint8_t p_fill[3];        /* Fill to 32 bits */
        /* Cache line 0x40 */
        struct hptsh {
                TAILQ_HEAD(, tcpcb)     head;
                uint32_t                count;
                uint32_t                gencnt;
        } *p_hptss;                     /* Hptsi wheel */
        uint32_t p_hpts_sleep_time;     /* Current sleep interval having a max
                                         * of 255ms */
        uint32_t overidden_sleep;       /* what was overrided by min-sleep for logging */
        uint32_t saved_lasttick;        /* for logging */
        uint32_t saved_curtick;         /* for logging */
        uint32_t saved_curslot;         /* for logging */
        uint32_t saved_prev_slot;       /* for logging */
        uint32_t p_delayed_by;  /* How much were we delayed by */
        /* Cache line 0x80 */
        struct sysctl_ctx_list hpts_ctx;
        struct sysctl_oid *hpts_root;
        struct intr_event *ie;
        void *ie_cookie;
        uint16_t p_num;         /* The hpts number one per cpu */
        uint16_t p_cpu;         /* The hpts CPU */
        /* There is extra space in here */
        /* Cache line 0x100 */
        struct callout co __aligned(CACHE_LINE_SIZE);
}               __aligned(CACHE_LINE_SIZE);

static struct tcp_hptsi {
        struct cpu_group **grps;
        struct tcp_hpts_entry **rp_ent; /* Array of hptss */
        uint32_t *cts_last_ran;
        uint32_t grp_cnt;
        uint32_t rp_num_hptss;  /* Number of hpts threads */
} tcp_pace;

static MALLOC_DEFINE(M_TCPHPTS, "tcp_hpts", "TCP hpts");
#ifdef RSS
static int tcp_bind_threads = 1;
#else
static int tcp_bind_threads = 2;
#endif
static int tcp_use_irq_cpu = 0;
static int hpts_does_tp_logging = 0;

static int32_t tcp_hptsi(struct tcp_hpts_entry *hpts, bool from_callout);
static void tcp_hpts_thread(void *ctx);

int32_t tcp_min_hptsi_time = DEFAULT_MIN_SLEEP;
static int conn_cnt_thresh = DEFAULT_CONNECTION_THESHOLD;
static int32_t dynamic_min_sleep = DYNAMIC_MIN_SLEEP;
static int32_t dynamic_max_sleep = DYNAMIC_MAX_SLEEP;


SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hpts, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "TCP Hpts controls");
SYSCTL_NODE(_net_inet_tcp_hpts, OID_AUTO, stats, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "TCP Hpts statistics");

#define timersub(tvp, uvp, vvp)                                         \
        do {                                                            \
                (vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec;          \
                (vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec;       \
                if ((vvp)->tv_usec < 0) {                               \
                        (vvp)->tv_sec--;                                \
                        (vvp)->tv_usec += 1000000;                      \
                }                                                       \
        } while (0)

static int32_t tcp_hpts_precision = 120;

static struct hpts_domain_info {
        int count;
        int cpu[MAXCPU];
} hpts_domains[MAXMEMDOM];

counter_u64_t hpts_hopelessly_behind;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, hopeless, CTLFLAG_RD,
    &hpts_hopelessly_behind,
    "Number of times hpts could not catch up and was behind hopelessly");

counter_u64_t hpts_loops;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, loops, CTLFLAG_RD,
    &hpts_loops, "Number of times hpts had to loop to catch up");

counter_u64_t back_tosleep;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, no_tcbsfound, CTLFLAG_RD,
    &back_tosleep, "Number of times hpts found no tcbs");

counter_u64_t combined_wheel_wrap;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, comb_wheel_wrap, CTLFLAG_RD,
    &combined_wheel_wrap, "Number of times the wheel lagged enough to have an insert see wrap");

counter_u64_t wheel_wrap;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, wheel_wrap, CTLFLAG_RD,
    &wheel_wrap, "Number of times the wheel lagged enough to have an insert see wrap");

counter_u64_t hpts_direct_call;
SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, direct_call, CTLFLAG_RD,
    &hpts_direct_call, "Number of times hpts was called by syscall/trap or other entry");

counter_u64_t hpts_wake_timeout;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, timeout_wakeup, CTLFLAG_RD,
    &hpts_wake_timeout, "Number of times hpts threads woke up via the callout expiring");

counter_u64_t hpts_direct_awakening;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, direct_awakening, CTLFLAG_RD,
    &hpts_direct_awakening, "Number of times hpts threads woke up via the callout expiring");

counter_u64_t hpts_back_tosleep;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, back_tosleep, CTLFLAG_RD,
    &hpts_back_tosleep, "Number of times hpts threads woke up via the callout expiring and went back to sleep no work");

counter_u64_t cpu_uses_flowid;
counter_u64_t cpu_uses_random;

SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, cpusel_flowid, CTLFLAG_RD,
    &cpu_uses_flowid, "Number of times when setting cpuid we used the flowid field");
SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, cpusel_random, CTLFLAG_RD,
    &cpu_uses_random, "Number of times when setting cpuid we used the a random value");

TUNABLE_INT("net.inet.tcp.bind_hptss", &tcp_bind_threads);
TUNABLE_INT("net.inet.tcp.use_irq", &tcp_use_irq_cpu);
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, bind_hptss, CTLFLAG_RD,
    &tcp_bind_threads, 2,
    "Thread Binding tunable");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, use_irq, CTLFLAG_RD,
    &tcp_use_irq_cpu, 0,
    "Use of irq CPU  tunable");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, precision, CTLFLAG_RW,
    &tcp_hpts_precision, 120,
    "Value for PRE() precision of callout");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, cnt_thresh, CTLFLAG_RW,
    &conn_cnt_thresh, 0,
    "How many connections (below) make us use the callout based mechanism");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, logging, CTLFLAG_RW,
    &hpts_does_tp_logging, 0,
    "Do we add to any tp that has logging on pacer logs");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, dyn_minsleep, CTLFLAG_RW,
    &dynamic_min_sleep, 250,
    "What is the dynamic minsleep value?");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, dyn_maxsleep, CTLFLAG_RW,
    &dynamic_max_sleep, 5000,
    "What is the dynamic maxsleep value?");

static int32_t max_pacer_loops = 10;
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, loopmax, CTLFLAG_RW,
    &max_pacer_loops, 10,
    "What is the maximum number of times the pacer will loop trying to catch up");

#define HPTS_MAX_SLEEP_ALLOWED (NUM_OF_HPTSI_SLOTS/2)

static uint32_t hpts_sleep_max = HPTS_MAX_SLEEP_ALLOWED;

static int
sysctl_net_inet_tcp_hpts_max_sleep(SYSCTL_HANDLER_ARGS)
{
        int error;
        uint32_t new;

        new = hpts_sleep_max;
        error = sysctl_handle_int(oidp, &new, 0, req);
        if (error == 0 && req->newptr) {
                if ((new < (dynamic_min_sleep/HPTS_TICKS_PER_SLOT)) ||
                     (new > HPTS_MAX_SLEEP_ALLOWED))
                        error = EINVAL;
                else
                        hpts_sleep_max = new;
        }
        return (error);
}

static int
sysctl_net_inet_tcp_hpts_min_sleep(SYSCTL_HANDLER_ARGS)
{
        int error;
        uint32_t new;

        new = tcp_min_hptsi_time;
        error = sysctl_handle_int(oidp, &new, 0, req);
        if (error == 0 && req->newptr) {
                if (new < LOWEST_SLEEP_ALLOWED)
                        error = EINVAL;
                else
                        tcp_min_hptsi_time = new;
        }
        return (error);
}

SYSCTL_PROC(_net_inet_tcp_hpts, OID_AUTO, maxsleep,
    CTLTYPE_UINT | CTLFLAG_RW,
    &hpts_sleep_max, 0,
    &sysctl_net_inet_tcp_hpts_max_sleep, "IU",
    "Maximum time hpts will sleep in slots");

SYSCTL_PROC(_net_inet_tcp_hpts, OID_AUTO, minsleep,
    CTLTYPE_UINT | CTLFLAG_RW,
    &tcp_min_hptsi_time, 0,
    &sysctl_net_inet_tcp_hpts_min_sleep, "IU",
    "The minimum time the hpts must sleep before processing more slots");

static int ticks_indicate_more_sleep = TICKS_INDICATE_MORE_SLEEP;
static int ticks_indicate_less_sleep = TICKS_INDICATE_LESS_SLEEP;
static int tcp_hpts_no_wake_over_thresh = 1;

SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, more_sleep, CTLFLAG_RW,
    &ticks_indicate_more_sleep, 0,
    "If we only process this many or less on a timeout, we need longer sleep on the next callout");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, less_sleep, CTLFLAG_RW,
    &ticks_indicate_less_sleep, 0,
    "If we process this many or more on a timeout, we need less sleep on the next callout");
SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, nowake_over_thresh, CTLFLAG_RW,
    &tcp_hpts_no_wake_over_thresh, 0,
    "When we are over the threshold on the pacer do we prohibit wakeups?");

static uint16_t
hpts_random_cpu(void)
{
        uint16_t cpuid;
        uint32_t ran;

        ran = arc4random();
        cpuid = (((ran & 0xffff) % mp_ncpus) % tcp_pace.rp_num_hptss);
        return (cpuid);
}

static void
tcp_hpts_log(struct tcp_hpts_entry *hpts, struct tcpcb *tp, struct timeval *tv,
    int slots_to_run, int idx, bool from_callout)
{
        union tcp_log_stackspecific log;
        /*
         * Unused logs are
         * 64 bit - delRate, rttProp, bw_inuse
         * 16 bit - cwnd_gain
         *  8 bit - bbr_state, bbr_substate, inhpts;
         */
        memset(&log.u_bbr, 0, sizeof(log.u_bbr));
        log.u_bbr.flex1 = hpts->p_nxt_slot;
        log.u_bbr.flex2 = hpts->p_cur_slot;
        log.u_bbr.flex3 = hpts->p_prev_slot;
        log.u_bbr.flex4 = idx;
        log.u_bbr.flex5 = hpts->p_curtick;
        log.u_bbr.flex6 = hpts->p_on_queue_cnt;
        log.u_bbr.flex7 = hpts->p_cpu;
        log.u_bbr.flex8 = (uint8_t)from_callout;
        log.u_bbr.inflight = slots_to_run;
        log.u_bbr.applimited = hpts->overidden_sleep;
        log.u_bbr.delivered = hpts->saved_curtick;
        log.u_bbr.timeStamp = tcp_tv_to_usectick(tv);
        log.u_bbr.epoch = hpts->saved_curslot;
        log.u_bbr.lt_epoch = hpts->saved_prev_slot;
        log.u_bbr.pkts_out = hpts->p_delayed_by;
        log.u_bbr.lost = hpts->p_hpts_sleep_time;
        log.u_bbr.pacing_gain = hpts->p_cpu;
        log.u_bbr.pkt_epoch = hpts->p_runningslot;
        log.u_bbr.use_lt_bw = 1;
        TCP_LOG_EVENTP(tp, NULL,
                       &tptosocket(tp)->so_rcv,
                       &tptosocket(tp)->so_snd,
                       BBR_LOG_HPTSDIAG, 0,
                       0, &log, false, tv);
}

static void
tcp_wakehpts(struct tcp_hpts_entry *hpts)
{
        HPTS_MTX_ASSERT(hpts);

        if (tcp_hpts_no_wake_over_thresh && (hpts->p_on_queue_cnt >= conn_cnt_thresh)) {
                hpts->p_direct_wake = 0;
                return;
        }
        if (hpts->p_hpts_wake_scheduled == 0) {
                hpts->p_hpts_wake_scheduled = 1;
                swi_sched(hpts->ie_cookie, 0);
        }
}

static void
hpts_timeout_swi(void *arg)
{
        struct tcp_hpts_entry *hpts;

        hpts = (struct tcp_hpts_entry *)arg;
        swi_sched(hpts->ie_cookie, 0);
}

static void
tcp_hpts_insert_internal(struct tcpcb *tp, struct tcp_hpts_entry *hpts)
{
        struct inpcb *inp = tptoinpcb(tp);
        struct hptsh *hptsh;

        INP_WLOCK_ASSERT(inp);
        HPTS_MTX_ASSERT(hpts);
        MPASS(hpts->p_cpu == tp->t_hpts_cpu);
        MPASS(!(inp->inp_flags & INP_DROPPED));

        hptsh = &hpts->p_hptss[tp->t_hpts_slot];

        if (tp->t_in_hpts == IHPTS_NONE) {
                tp->t_in_hpts = IHPTS_ONQUEUE;
                in_pcbref(inp);
        } else if (tp->t_in_hpts == IHPTS_MOVING) {
                tp->t_in_hpts = IHPTS_ONQUEUE;
        } else
                MPASS(tp->t_in_hpts == IHPTS_ONQUEUE);
        tp->t_hpts_gencnt = hptsh->gencnt;

        TAILQ_INSERT_TAIL(&hptsh->head, tp, t_hpts);
        hptsh->count++;
        hpts->p_on_queue_cnt++;
}

static struct tcp_hpts_entry *
tcp_hpts_lock(struct tcpcb *tp)
{
        struct tcp_hpts_entry *hpts;

        INP_LOCK_ASSERT(tptoinpcb(tp));

        hpts = tcp_pace.rp_ent[tp->t_hpts_cpu];
        HPTS_LOCK(hpts);

        return (hpts);
}

static void
tcp_hpts_release(struct tcpcb *tp)
{
        bool released __diagused;

        tp->t_in_hpts = IHPTS_NONE;
        released = in_pcbrele_wlocked(tptoinpcb(tp));
        MPASS(released == false);
}

/*
 * Initialize tcpcb to get ready for use with HPTS.  We will know which CPU
 * is preferred on the first incoming packet.  Before that avoid crowding
 * a single CPU with newborn connections and use a random one.
 * This initialization is normally called on a newborn tcpcb, but potentially
 * can be called once again if stack is switched.  In that case we inherit CPU
 * that the previous stack has set, be it random or not.  In extreme cases,
 * e.g. syzkaller fuzzing, a tcpcb can already be in HPTS in IHPTS_MOVING state
 * and has never received a first packet.
 */
void
tcp_hpts_init(struct tcpcb *tp)
{

        if (__predict_true(tp->t_hpts_cpu == HPTS_CPU_NONE)) {
                tp->t_hpts_cpu = hpts_random_cpu();
                MPASS(!(tp->t_flags2 & TF2_HPTS_CPU_SET));
        }
}

/*
 * Called normally with the INP_LOCKED but it
 * does not matter, the hpts lock is the key
 * but the lock order allows us to hold the
 * INP lock and then get the hpts lock.
 */
void
tcp_hpts_remove(struct tcpcb *tp)
{
        struct tcp_hpts_entry *hpts;
        struct hptsh *hptsh;

        INP_WLOCK_ASSERT(tptoinpcb(tp));

        hpts = tcp_hpts_lock(tp);
        if (tp->t_in_hpts == IHPTS_ONQUEUE) {
                hptsh = &hpts->p_hptss[tp->t_hpts_slot];
                tp->t_hpts_request = 0;
                if (__predict_true(tp->t_hpts_gencnt == hptsh->gencnt)) {
                        TAILQ_REMOVE(&hptsh->head, tp, t_hpts);
                        MPASS(hptsh->count > 0);
                        hptsh->count--;
                        MPASS(hpts->p_on_queue_cnt > 0);
                        hpts->p_on_queue_cnt--;
                        tcp_hpts_release(tp);
                } else {
                        /*
                         * tcp_hptsi() now owns the TAILQ head of this inp.
                         * Can't TAILQ_REMOVE, just mark it.
                         */
#ifdef INVARIANTS
                        struct tcpcb *tmp;

                        TAILQ_FOREACH(tmp, &hptsh->head, t_hpts)
                                MPASS(tmp != tp);
#endif
                        tp->t_in_hpts = IHPTS_MOVING;
                        tp->t_hpts_slot = -1;
                }
        } else if (tp->t_in_hpts == IHPTS_MOVING) {
                /*
                 * Handle a special race condition:
                 * tcp_hptsi() moves inpcb to detached tailq
                 * tcp_hpts_remove() marks as IHPTS_MOVING, slot = -1
                 * tcp_hpts_insert() sets slot to a meaningful value
                 * tcp_hpts_remove() again (we are here!), then in_pcbdrop()
                 * tcp_hptsi() finds pcb with meaningful slot and INP_DROPPED
                 */
                tp->t_hpts_slot = -1;
        }
        HPTS_UNLOCK(hpts);
}

static inline int
hpts_slot(uint32_t wheel_slot, uint32_t plus)
{
        /*
         * Given a slot on the wheel, what slot
         * is that plus ticks out?
         */
        KASSERT(wheel_slot < NUM_OF_HPTSI_SLOTS, ("Invalid tick %u not on wheel", wheel_slot));
        return ((wheel_slot + plus) % NUM_OF_HPTSI_SLOTS);
}

static inline int
tick_to_wheel(uint32_t cts_in_wticks)
{
        /*
         * Given a timestamp in ticks (so by
         * default to get it to a real time one
         * would multiply by 10.. i.e the number
         * of ticks in a slot) map it to our limited
         * space wheel.
         */
        return (cts_in_wticks % NUM_OF_HPTSI_SLOTS);
}

static inline int
hpts_slots_diff(int prev_slot, int slot_now)
{
        /*
         * Given two slots that are someplace
         * on our wheel. How far are they apart?
         */
        if (slot_now > prev_slot)
                return (slot_now - prev_slot);
        else if (slot_now == prev_slot)
                /*
                 * Special case, same means we can go all of our
                 * wheel less one slot.
                 */
                return (NUM_OF_HPTSI_SLOTS - 1);
        else
                return ((NUM_OF_HPTSI_SLOTS - prev_slot) + slot_now);
}

/*
 * Given a slot on the wheel that is the current time
 * mapped to the wheel (wheel_slot), what is the maximum
 * distance forward that can be obtained without
 * wrapping past either prev_slot or running_slot
 * depending on the htps state? Also if passed
 * a uint32_t *, fill it with the slot location.
 *
 * Note if you do not give this function the current
 * time (that you think it is) mapped to the wheel slot
 * then the results will not be what you expect and
 * could lead to invalid inserts.
 */
static inline int32_t
max_slots_available(struct tcp_hpts_entry *hpts, uint32_t wheel_slot, uint32_t *target_slot)
{
        uint32_t dis_to_travel, end_slot, pacer_to_now, avail_on_wheel;

        if ((hpts->p_hpts_active == 1) &&
            (hpts->p_wheel_complete == 0)) {
                end_slot = hpts->p_runningslot;
                /* Back up one tick */
                if (end_slot == 0)
                        end_slot = NUM_OF_HPTSI_SLOTS - 1;
                else
                        end_slot--;
                if (target_slot)
                        *target_slot = end_slot;
        } else {
                /*
                 * For the case where we are
                 * not active, or we have
                 * completed the pass over
                 * the wheel, we can use the
                 * prev tick and subtract one from it. This puts us
                 * as far out as possible on the wheel.
                 */
                end_slot = hpts->p_prev_slot;
                if (end_slot == 0)
                        end_slot = NUM_OF_HPTSI_SLOTS - 1;
                else
                        end_slot--;
                if (target_slot)
                        *target_slot = end_slot;
                /*
                 * Now we have close to the full wheel left minus the
                 * time it has been since the pacer went to sleep. Note
                 * that wheel_tick, passed in, should be the current time
                 * from the perspective of the caller, mapped to the wheel.
                 */
                if (hpts->p_prev_slot != wheel_slot)
                        dis_to_travel = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);
                else
                        dis_to_travel = 1;
                /*
                 * dis_to_travel in this case is the space from when the
                 * pacer stopped (p_prev_slot) and where our wheel_slot
                 * is now. To know how many slots we can put it in we
                 * subtract from the wheel size. We would not want
                 * to place something after p_prev_slot or it will
                 * get ran too soon.
                 */
                return (NUM_OF_HPTSI_SLOTS - dis_to_travel);
        }
        /*
         * So how many slots are open between p_runningslot -> p_cur_slot
         * that is what is currently un-available for insertion. Special
         * case when we are at the last slot, this gets 1, so that
         * the answer to how many slots are available is all but 1.
         */
        if (hpts->p_runningslot == hpts->p_cur_slot)
                dis_to_travel = 1;
        else
                dis_to_travel = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
        /*
         * How long has the pacer been running?
         */
        if (hpts->p_cur_slot != wheel_slot) {
                /* The pacer is a bit late */
                pacer_to_now = hpts_slots_diff(hpts->p_cur_slot, wheel_slot);
        } else {
                /* The pacer is right on time, now == pacers start time */
                pacer_to_now = 0;
        }
        /*
         * To get the number left we can insert into we simply
         * subtract the distance the pacer has to run from how
         * many slots there are.
         */
        avail_on_wheel = NUM_OF_HPTSI_SLOTS - dis_to_travel;
        /*
         * Now how many of those we will eat due to the pacer's
         * time (p_cur_slot) of start being behind the
         * real time (wheel_slot)?
         */
        if (avail_on_wheel <= pacer_to_now) {
                /*
                 * Wheel wrap, we can't fit on the wheel, that
                 * is unusual the system must be way overloaded!
                 * Insert into the assured slot, and return special
                 * "0".
                 */
                counter_u64_add(combined_wheel_wrap, 1);
                if (target_slot)
                        *target_slot = hpts->p_nxt_slot;
                return (0);
        } else {
                /*
                 * We know how many slots are open
                 * on the wheel (the reverse of what
                 * is left to run. Take away the time
                 * the pacer started to now (wheel_slot)
                 * and that tells you how many slots are
                 * open that can be inserted into that won't
                 * be touched by the pacer until later.
                 */
                return (avail_on_wheel - pacer_to_now);
        }
}


#ifdef INVARIANTS
static void
check_if_slot_would_be_wrong(struct tcp_hpts_entry *hpts, struct tcpcb *tp,
    uint32_t hptsslot, int line)
{
        /*
         * Sanity checks for the pacer with invariants
         * on insert.
         */
        KASSERT(hptsslot < NUM_OF_HPTSI_SLOTS,
                ("hpts:%p tp:%p slot:%d > max", hpts, tp, hptsslot));
        if ((hpts->p_hpts_active) &&
            (hpts->p_wheel_complete == 0)) {
                /*
                 * If the pacer is processing a arc
                 * of the wheel, we need to make
                 * sure we are not inserting within
                 * that arc.
                 */
                int distance, yet_to_run;

                distance = hpts_slots_diff(hpts->p_runningslot, hptsslot);
                if (hpts->p_runningslot != hpts->p_cur_slot)
                        yet_to_run = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
                else
                        yet_to_run = 0; /* processing last slot */
                KASSERT(yet_to_run <= distance, ("hpts:%p tp:%p slot:%d "
                    "distance:%d yet_to_run:%d rs:%d cs:%d", hpts, tp,
                    hptsslot, distance, yet_to_run, hpts->p_runningslot,
                    hpts->p_cur_slot));
        }
}
#endif

uint32_t
tcp_hpts_insert_diag(struct tcpcb *tp, uint32_t slot, int32_t line, struct hpts_diag *diag)
{
        struct tcp_hpts_entry *hpts;
        struct timeval tv;
        uint32_t slot_on, wheel_cts, last_slot, need_new_to = 0;
        int32_t wheel_slot, maxslots;
        bool need_wakeup = false;

        INP_WLOCK_ASSERT(tptoinpcb(tp));
        MPASS(!(tptoinpcb(tp)->inp_flags & INP_DROPPED));
        MPASS(!(tp->t_in_hpts == IHPTS_ONQUEUE));

        /*
         * We now return the next-slot the hpts will be on, beyond its
         * current run (if up) or where it was when it stopped if it is
         * sleeping.
         */
        hpts = tcp_hpts_lock(tp);
        microuptime(&tv);
        if (diag) {
                memset(diag, 0, sizeof(struct hpts_diag));
                diag->p_hpts_active = hpts->p_hpts_active;
                diag->p_prev_slot = hpts->p_prev_slot;
                diag->p_runningslot = hpts->p_runningslot;
                diag->p_nxt_slot = hpts->p_nxt_slot;
                diag->p_cur_slot = hpts->p_cur_slot;
                diag->p_curtick = hpts->p_curtick;
                diag->p_lasttick = hpts->p_lasttick;
                diag->slot_req = slot;
                diag->p_on_min_sleep = hpts->p_on_min_sleep;
                diag->hpts_sleep_time = hpts->p_hpts_sleep_time;
        }
        if (slot == 0) {
                /* Ok we need to set it on the hpts in the current slot */
                tp->t_hpts_request = 0;
                if ((hpts->p_hpts_active == 0) || (hpts->p_wheel_complete)) {
                        /*
                         * A sleeping hpts we want in next slot to run
                         * note that in this state p_prev_slot == p_cur_slot
                         */
                        tp->t_hpts_slot = hpts_slot(hpts->p_prev_slot, 1);
                        if ((hpts->p_on_min_sleep == 0) &&
                            (hpts->p_hpts_active == 0))
                                need_wakeup = true;
                } else
                        tp->t_hpts_slot = hpts->p_runningslot;
                if (__predict_true(tp->t_in_hpts != IHPTS_MOVING))
                        tcp_hpts_insert_internal(tp, hpts);
                if (need_wakeup) {
                        /*
                         * Activate the hpts if it is sleeping and its
                         * timeout is not 1.
                         */
                        hpts->p_direct_wake = 1;
                        tcp_wakehpts(hpts);
                }
                slot_on = hpts->p_nxt_slot;
                HPTS_UNLOCK(hpts);

                return (slot_on);
        }
        /* Get the current time relative to the wheel */
        wheel_cts = tcp_tv_to_hptstick(&tv);
        /* Map it onto the wheel */
        wheel_slot = tick_to_wheel(wheel_cts);
        /* Now what's the max we can place it at? */
        maxslots = max_slots_available(hpts, wheel_slot, &last_slot);
        if (diag) {
                diag->wheel_slot = wheel_slot;
                diag->maxslots = maxslots;
                diag->wheel_cts = wheel_cts;
        }
        if (maxslots == 0) {
                /* The pacer is in a wheel wrap behind, yikes! */
                if (slot > 1) {
                        /*
                         * Reduce by 1 to prevent a forever loop in
                         * case something else is wrong. Note this
                         * probably does not hurt because the pacer
                         * if its true is so far behind we will be
                         * > 1second late calling anyway.
                         */
                        slot--;
                }
                tp->t_hpts_slot = last_slot;
                tp->t_hpts_request = slot;
        } else  if (maxslots >= slot) {
                /* It all fits on the wheel */
                tp->t_hpts_request = 0;
                tp->t_hpts_slot = hpts_slot(wheel_slot, slot);
        } else {
                /* It does not fit */
                tp->t_hpts_request = slot - maxslots;
                tp->t_hpts_slot = last_slot;
        }
        if (diag) {
                diag->slot_remaining = tp->t_hpts_request;
                diag->inp_hptsslot = tp->t_hpts_slot;
        }
#ifdef INVARIANTS
        check_if_slot_would_be_wrong(hpts, tp, tp->t_hpts_slot, line);
#endif
        if (__predict_true(tp->t_in_hpts != IHPTS_MOVING))
                tcp_hpts_insert_internal(tp, hpts);
        if ((hpts->p_hpts_active == 0) &&
            (tp->t_hpts_request == 0) &&
            (hpts->p_on_min_sleep == 0)) {
                /*
                 * The hpts is sleeping and NOT on a minimum
                 * sleep time, we need to figure out where
                 * it will wake up at and if we need to reschedule
                 * its time-out.
                 */
                uint32_t have_slept, yet_to_sleep;

                /* Now do we need to restart the hpts's timer? */
                have_slept = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);
                if (have_slept < hpts->p_hpts_sleep_time)
                        yet_to_sleep = hpts->p_hpts_sleep_time - have_slept;
                else {
                        /* We are over-due */
                        yet_to_sleep = 0;
                        need_wakeup = 1;
                }
                if (diag) {
                        diag->have_slept = have_slept;
                        diag->yet_to_sleep = yet_to_sleep;
                }
                if (yet_to_sleep &&
                    (yet_to_sleep > slot)) {
                        /*
                         * We need to reschedule the hpts's time-out.
                         */
                        hpts->p_hpts_sleep_time = slot;
                        need_new_to = slot * HPTS_TICKS_PER_SLOT;
                }
        }
        /*
         * Now how far is the hpts sleeping to? if active is 1, its
         * up and ticking we do nothing, otherwise we may need to
         * reschedule its callout if need_new_to is set from above.
         */
        if (need_wakeup) {
                hpts->p_direct_wake = 1;
                tcp_wakehpts(hpts);
                if (diag) {
                        diag->need_new_to = 0;
                        diag->co_ret = 0xffff0000;
                }
        } else if (need_new_to) {
                int32_t co_ret;
                struct timeval tv;
                sbintime_t sb;

                tv.tv_sec = 0;
                tv.tv_usec = 0;
                while (need_new_to > HPTS_USEC_IN_SEC) {
                        tv.tv_sec++;
                        need_new_to -= HPTS_USEC_IN_SEC;
                }
                tv.tv_usec = need_new_to;
                sb = tvtosbt(tv);
                co_ret = callout_reset_sbt_on(&hpts->co, sb, 0,
                                              hpts_timeout_swi, hpts, hpts->p_cpu,
                                              (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
                if (diag) {
                        diag->need_new_to = need_new_to;
                        diag->co_ret = co_ret;
                }
        }
        slot_on = hpts->p_nxt_slot;
        HPTS_UNLOCK(hpts);

        return (slot_on);
}

static uint16_t
hpts_cpuid(struct tcpcb *tp, int *failed)
{
        struct inpcb *inp = tptoinpcb(tp);
        u_int cpuid;
#ifdef NUMA
        struct hpts_domain_info *di;
#endif

        *failed = 0;
        if (tp->t_flags2 & TF2_HPTS_CPU_SET) {
                return (tp->t_hpts_cpu);
        }
        /*
         * If we are using the irq cpu set by LRO or
         * the driver then it overrides all other domains.
         */
        if (tcp_use_irq_cpu) {
                if (tp->t_lro_cpu == HPTS_CPU_NONE) {
                        *failed = 1;
                        return (0);
                }
                return (tp->t_lro_cpu);
        }
        /* If one is set the other must be the same */
#ifdef RSS
        cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
        if (cpuid == NETISR_CPUID_NONE)
                return (hpts_random_cpu());
        else
                return (cpuid);
#endif
        /*
         * We don't have a flowid -> cpuid mapping, so cheat and just map
         * unknown cpuids to curcpu.  Not the best, but apparently better
         * than defaulting to swi 0.
         */
        if (inp->inp_flowtype == M_HASHTYPE_NONE) {
                counter_u64_add(cpu_uses_random, 1);
                return (hpts_random_cpu());
        }
        /*
         * Hash to a thread based on the flowid.  If we are using numa,
         * then restrict the hash to the numa domain where the inp lives.
         */

#ifdef NUMA
        if ((vm_ndomains == 1) ||
            (inp->inp_numa_domain == M_NODOM)) {
#endif
                cpuid = inp->inp_flowid % mp_ncpus;
#ifdef NUMA
        } else {
                /* Hash into the cpu's that use that domain */
                di = &hpts_domains[inp->inp_numa_domain];
                cpuid = di->cpu[inp->inp_flowid % di->count];
        }
#endif
        counter_u64_add(cpu_uses_flowid, 1);
        return (cpuid);
}

static void
tcp_hpts_set_max_sleep(struct tcp_hpts_entry *hpts, int wrap_loop_cnt)
{
        uint32_t t = 0, i;

        if ((hpts->p_on_queue_cnt) && (wrap_loop_cnt < 2)) {
                /*
                 * Find next slot that is occupied and use that to
                 * be the sleep time.
                 */
                for (i = 0, t = hpts_slot(hpts->p_cur_slot, 1); i < NUM_OF_HPTSI_SLOTS; i++) {
                        if (TAILQ_EMPTY(&hpts->p_hptss[t].head) == 0) {
                                break;
                        }
                        t = (t + 1) % NUM_OF_HPTSI_SLOTS;
                }
                KASSERT((i != NUM_OF_HPTSI_SLOTS), ("Hpts:%p cnt:%d but none found", hpts, hpts->p_on_queue_cnt));
                hpts->p_hpts_sleep_time = min((i + 1), hpts_sleep_max);
        } else {
                /* No one on the wheel sleep for all but 400 slots or sleep max  */
                hpts->p_hpts_sleep_time = hpts_sleep_max;
        }
}

static int32_t
tcp_hptsi(struct tcp_hpts_entry *hpts, bool from_callout)
{
        struct tcpcb *tp;
        struct timeval tv;
        int32_t slots_to_run, i, error;
        int32_t loop_cnt = 0;
        int32_t did_prefetch = 0;
        int32_t prefetch_tp = 0;
        int32_t wrap_loop_cnt = 0;
        int32_t slot_pos_of_endpoint = 0;
        int32_t orig_exit_slot;
        bool completed_measure, seen_endpoint;

        completed_measure = false;
        seen_endpoint = false;

        HPTS_MTX_ASSERT(hpts);
        NET_EPOCH_ASSERT();
        /* record previous info for any logging */
        hpts->saved_lasttick = hpts->p_lasttick;
        hpts->saved_curtick = hpts->p_curtick;
        hpts->saved_curslot = hpts->p_cur_slot;
        hpts->saved_prev_slot = hpts->p_prev_slot;

        hpts->p_lasttick = hpts->p_curtick;
        hpts->p_curtick = tcp_gethptstick(&tv);
        tcp_pace.cts_last_ran[hpts->p_num] = tcp_tv_to_usectick(&tv);
        orig_exit_slot = hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
        if ((hpts->p_on_queue_cnt == 0) ||
            (hpts->p_lasttick == hpts->p_curtick)) {
                /*
                 * No time has yet passed,
                 * or nothing to do.
                 */
                hpts->p_prev_slot = hpts->p_cur_slot;
                hpts->p_lasttick = hpts->p_curtick;
                goto no_run;
        }
again:
        hpts->p_wheel_complete = 0;
        HPTS_MTX_ASSERT(hpts);
        slots_to_run = hpts_slots_diff(hpts->p_prev_slot, hpts->p_cur_slot);
        if (((hpts->p_curtick - hpts->p_lasttick) >
             ((NUM_OF_HPTSI_SLOTS-1) * HPTS_TICKS_PER_SLOT)) &&
            (hpts->p_on_queue_cnt != 0)) {
                /*
                 * Wheel wrap is occuring, basically we
                 * are behind and the distance between
                 * run's has spread so much it has exceeded
                 * the time on the wheel (1.024 seconds). This
                 * is ugly and should NOT be happening. We
                 * need to run the entire wheel. We last processed
                 * p_prev_slot, so that needs to be the last slot
                 * we run. The next slot after that should be our
                 * reserved first slot for new, and then starts
                 * the running position. Now the problem is the
                 * reserved "not to yet" place does not exist
                 * and there may be inp's in there that need
                 * running. We can merge those into the
                 * first slot at the head.
                 */
                wrap_loop_cnt++;
                hpts->p_nxt_slot = hpts_slot(hpts->p_prev_slot, 1);
                hpts->p_runningslot = hpts_slot(hpts->p_prev_slot, 2);
                /*
                 * Adjust p_cur_slot to be where we are starting from
                 * hopefully we will catch up (fat chance if something
                 * is broken this bad :( )
                 */
                hpts->p_cur_slot = hpts->p_prev_slot;
                /*
                 * The next slot has guys to run too, and that would
                 * be where we would normally start, lets move them into
                 * the next slot (p_prev_slot + 2) so that we will
                 * run them, the extra 10usecs of late (by being
                 * put behind) does not really matter in this situation.
                 */
                TAILQ_FOREACH(tp, &hpts->p_hptss[hpts->p_nxt_slot].head,
                    t_hpts) {
                        MPASS(tp->t_hpts_slot == hpts->p_nxt_slot);
                        MPASS(tp->t_hpts_gencnt ==
                            hpts->p_hptss[hpts->p_nxt_slot].gencnt);
                        MPASS(tp->t_in_hpts == IHPTS_ONQUEUE);

                        /*
                         * Update gencnt and nextslot accordingly to match
                         * the new location. This is safe since it takes both
                         * the INP lock and the pacer mutex to change the
                         * t_hptsslot and t_hpts_gencnt.
                         */
                        tp->t_hpts_gencnt =
                            hpts->p_hptss[hpts->p_runningslot].gencnt;
                        tp->t_hpts_slot = hpts->p_runningslot;
                }
                TAILQ_CONCAT(&hpts->p_hptss[hpts->p_runningslot].head,
                    &hpts->p_hptss[hpts->p_nxt_slot].head, t_hpts);
                hpts->p_hptss[hpts->p_runningslot].count +=
                    hpts->p_hptss[hpts->p_nxt_slot].count;
                hpts->p_hptss[hpts->p_nxt_slot].count = 0;
                hpts->p_hptss[hpts->p_nxt_slot].gencnt++;
                slots_to_run = NUM_OF_HPTSI_SLOTS - 1;
                counter_u64_add(wheel_wrap, 1);
        } else {
                /*
                 * Nxt slot is always one after p_runningslot though
                 * its not used usually unless we are doing wheel wrap.
                 */
                hpts->p_nxt_slot = hpts->p_prev_slot;
                hpts->p_runningslot = hpts_slot(hpts->p_prev_slot, 1);
        }
        if (hpts->p_on_queue_cnt == 0) {
                goto no_one;
        }
        for (i = 0; i < slots_to_run; i++) {
                struct tcpcb *tp, *ntp;
                TAILQ_HEAD(, tcpcb) head = TAILQ_HEAD_INITIALIZER(head);
                struct hptsh *hptsh;
                uint32_t runningslot;

                /*
                 * Calculate our delay, if there are no extra ticks there
                 * was not any (i.e. if slots_to_run == 1, no delay).
                 */
                hpts->p_delayed_by = (slots_to_run - (i + 1)) *
                    HPTS_TICKS_PER_SLOT;

                runningslot = hpts->p_runningslot;
                hptsh = &hpts->p_hptss[runningslot];
                TAILQ_SWAP(&head, &hptsh->head, tcpcb, t_hpts);
                hpts->p_on_queue_cnt -= hptsh->count;
                hptsh->count = 0;
                hptsh->gencnt++;

                HPTS_UNLOCK(hpts);

                TAILQ_FOREACH_SAFE(tp, &head, t_hpts, ntp) {
                        struct inpcb *inp = tptoinpcb(tp);
                        bool set_cpu;

                        if (ntp != NULL) {
                                /*
                                 * If we have a next tcpcb, see if we can
                                 * prefetch it. Note this may seem
                                 * "risky" since we have no locks (other
                                 * than the previous inp) and there no
                                 * assurance that ntp was not pulled while
                                 * we were processing tp and freed. If this
                                 * occurred it could mean that either:
                                 *
                                 * a) Its NULL (which is fine we won't go
                                 * here) <or> b) Its valid (which is cool we
                                 * will prefetch it) <or> c) The inp got
                                 * freed back to the slab which was
                                 * reallocated. Then the piece of memory was
                                 * re-used and something else (not an
                                 * address) is in inp_ppcb. If that occurs
                                 * we don't crash, but take a TLB shootdown
                                 * performance hit (same as if it was NULL
                                 * and we tried to pre-fetch it).
                                 *
                                 * Considering that the likelyhood of <c> is
                                 * quite rare we will take a risk on doing
                                 * this. If performance drops after testing
                                 * we can always take this out. NB: the
                                 * kern_prefetch on amd64 actually has
                                 * protection against a bad address now via
                                 * the DMAP_() tests. This will prevent the
                                 * TLB hit, and instead if <c> occurs just
                                 * cause us to load cache with a useless
                                 * address (to us).
                                 *
                                 * XXXGL: this comment and the prefetch action
                                 * could be outdated after tp == inp change.
                                 */
                                kern_prefetch(ntp, &prefetch_tp);
                                prefetch_tp = 1;
                        }

                        /* For debugging */
                        if (!seen_endpoint) {
                                seen_endpoint = true;
                                orig_exit_slot = slot_pos_of_endpoint =
                                    runningslot;
                        } else if (!completed_measure) {
                                /* Record the new position */
                                orig_exit_slot = runningslot;
                        }

                        INP_WLOCK(inp);
                        if ((tp->t_flags2 & TF2_HPTS_CPU_SET) == 0) {
                                set_cpu = true;
                        } else {
                                set_cpu = false;
                        }

                        if (__predict_false(tp->t_in_hpts == IHPTS_MOVING)) {
                                if (tp->t_hpts_slot == -1) {
                                        tp->t_in_hpts = IHPTS_NONE;
                                        if (in_pcbrele_wlocked(inp) == false)
                                                INP_WUNLOCK(inp);
                                } else {
                                        HPTS_LOCK(hpts);
                                        tcp_hpts_insert_internal(tp, hpts);
                                        HPTS_UNLOCK(hpts);
                                        INP_WUNLOCK(inp);
                                }
                                continue;
                        }

                        MPASS(tp->t_in_hpts == IHPTS_ONQUEUE);
                        MPASS(!(inp->inp_flags & INP_DROPPED));
                        KASSERT(runningslot == tp->t_hpts_slot,
                                ("Hpts:%p inp:%p slot mis-aligned %u vs %u",
                                 hpts, inp, runningslot, tp->t_hpts_slot));

                        if (tp->t_hpts_request) {
                                /*
                                 * This guy is deferred out further in time
                                 * then our wheel had available on it.
                                 * Push him back on the wheel or run it
                                 * depending.
                                 */
                                uint32_t maxslots, last_slot, remaining_slots;

                                remaining_slots = slots_to_run - (i + 1);
                                if (tp->t_hpts_request > remaining_slots) {
                                        HPTS_LOCK(hpts);
                                        /*
                                         * How far out can we go?
                                         */
                                        maxslots = max_slots_available(hpts,
                                            hpts->p_cur_slot, &last_slot);
                                        if (maxslots >= tp->t_hpts_request) {
                                                /* We can place it finally to
                                                 * be processed.  */
                                                tp->t_hpts_slot = hpts_slot(
                                                    hpts->p_runningslot,
                                                    tp->t_hpts_request);
                                                tp->t_hpts_request = 0;
                                        } else {
                                                /* Work off some more time */
                                                tp->t_hpts_slot = last_slot;
                                                tp->t_hpts_request -=
                                                    maxslots;
                                        }
                                        tcp_hpts_insert_internal(tp, hpts);
                                        HPTS_UNLOCK(hpts);
                                        INP_WUNLOCK(inp);
                                        continue;
                                }
                                tp->t_hpts_request = 0;
                                /* Fall through we will so do it now */
                        }

                        tcp_hpts_release(tp);
                        if (set_cpu) {
                                /*
                                 * Setup so the next time we will move to
                                 * the right CPU. This should be a rare
                                 * event. It will sometimes happens when we
                                 * are the client side (usually not the
                                 * server). Somehow tcp_output() gets called
                                 * before the tcp_do_segment() sets the
                                 * intial state. This means the r_cpu and
                                 * r_hpts_cpu is 0. We get on the hpts, and
                                 * then tcp_input() gets called setting up
                                 * the r_cpu to the correct value. The hpts
                                 * goes off and sees the mis-match. We
                                 * simply correct it here and the CPU will
                                 * switch to the new hpts nextime the tcb
                                 * gets added to the hpts (not this one)
                                 * :-)
                                 */
                                tcp_set_hpts(tp);
                        }
                        CURVNET_SET(inp->inp_vnet);
                        /* Lets do any logging that we might want to */
                        if (hpts_does_tp_logging && tcp_bblogging_on(tp)) {
                                tcp_hpts_log(hpts, tp, &tv, slots_to_run, i,
                                    from_callout);
                        }

                        if (tp->t_fb_ptr != NULL) {
                                kern_prefetch(tp->t_fb_ptr, &did_prefetch);
                                did_prefetch = 1;
                        }
                        /*
                         * We set TF2_HPTS_CALLS before any possible output.
                         * The contract with the transport is that if it cares
                         * about hpts calling it should clear the flag. That
                         * way next time it is called it will know it is hpts.
                         *
                         * We also only call tfb_do_queued_segments() <or>
                         * tcp_output().  It is expected that if segments are
                         * queued and come in that the final input mbuf will
                         * cause a call to output if it is needed so we do
                         * not need a second call to tcp_output(). So we do
                         * one or the other but not both.
                         *
                         * XXXGL: some KPI abuse here.  tfb_do_queued_segments
                         * returns unlocked with positive error (always 1) and
                         * tcp_output returns unlocked with negative error.
                         */
                        tp->t_flags2 |= TF2_HPTS_CALLS;
                        if ((tp->t_flags2 & TF2_SUPPORTS_MBUFQ) &&
                            !STAILQ_EMPTY(&tp->t_inqueue))
                                error = -(*tp->t_fb->tfb_do_queued_segments)(tp,
                                    0);
                        else
                                error = tcp_output(tp);
                        if (__predict_true(error >= 0))
                                INP_WUNLOCK(inp);
                        CURVNET_RESTORE();
                }
                if (seen_endpoint) {
                        /*
                         * We now have a accurate distance between
                         * slot_pos_of_endpoint <-> orig_exit_slot
                         * to tell us how late we were, orig_exit_slot
                         * is where we calculated the end of our cycle to
                         * be when we first entered.
                         */
                        completed_measure = true;
                }
                HPTS_LOCK(hpts);
                hpts->p_runningslot++;
                if (hpts->p_runningslot >= NUM_OF_HPTSI_SLOTS) {
                        hpts->p_runningslot = 0;
                }
        }
no_one:
        HPTS_MTX_ASSERT(hpts);
        hpts->p_delayed_by = 0;
        /*
         * Check to see if we took an excess amount of time and need to run
         * more ticks (if we did not hit eno-bufs).
         */
        hpts->p_prev_slot = hpts->p_cur_slot;
        hpts->p_lasttick = hpts->p_curtick;
        if (!from_callout || (loop_cnt > max_pacer_loops)) {
                /*
                 * Something is serious slow we have
                 * looped through processing the wheel
                 * and by the time we cleared the
                 * needs to run max_pacer_loops time
                 * we still needed to run. That means
                 * the system is hopelessly behind and
                 * can never catch up :(
                 *
                 * We will just lie to this thread
                 * and let it thing p_curtick is
                 * correct. When it next awakens
                 * it will find itself further behind.
                 */
                if (from_callout)
                        counter_u64_add(hpts_hopelessly_behind, 1);
                goto no_run;
        }
        hpts->p_curtick = tcp_gethptstick(&tv);
        hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
        if (!seen_endpoint) {
                /* We saw no endpoint but we may be looping */
                orig_exit_slot = hpts->p_cur_slot;
        }
        if ((wrap_loop_cnt < 2) &&
            (hpts->p_lasttick != hpts->p_curtick)) {
                counter_u64_add(hpts_loops, 1);
                loop_cnt++;
                goto again;
        }
no_run:
        tcp_pace.cts_last_ran[hpts->p_num] = tcp_tv_to_usectick(&tv);
        /*
         * Set flag to tell that we are done for
         * any slot input that happens during
         * input.
         */
        hpts->p_wheel_complete = 1;
        /*
         * Now did we spend too long running input and need to run more ticks?
         * Note that if wrap_loop_cnt < 2 then we should have the conditions
         * in the KASSERT's true. But if the wheel is behind i.e. wrap_loop_cnt
         * is greater than 2, then the condtion most likely are *not* true.
         * Also if we are called not from the callout, we don't run the wheel
         * multiple times so the slots may not align either.
         */
        KASSERT(((hpts->p_prev_slot == hpts->p_cur_slot) ||
                 (wrap_loop_cnt >= 2) || !from_callout),
                ("H:%p p_prev_slot:%u not equal to p_cur_slot:%u", hpts,
                 hpts->p_prev_slot, hpts->p_cur_slot));
        KASSERT(((hpts->p_lasttick == hpts->p_curtick)
                 || (wrap_loop_cnt >= 2) || !from_callout),
                ("H:%p p_lasttick:%u not equal to p_curtick:%u", hpts,
                 hpts->p_lasttick, hpts->p_curtick));
        if (from_callout && (hpts->p_lasttick != hpts->p_curtick)) {
                hpts->p_curtick = tcp_gethptstick(&tv);
                counter_u64_add(hpts_loops, 1);
                hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
                goto again;
        }

        if (from_callout) {
                tcp_hpts_set_max_sleep(hpts, wrap_loop_cnt);
        }
        if (seen_endpoint)
                return(hpts_slots_diff(slot_pos_of_endpoint, orig_exit_slot));
        else
                return (0);
}

void
__tcp_set_hpts(struct tcpcb *tp, int32_t line)
{
        struct tcp_hpts_entry *hpts;
        int failed;

        INP_WLOCK_ASSERT(tptoinpcb(tp));

        hpts = tcp_hpts_lock(tp);
        if (tp->t_in_hpts == IHPTS_NONE && !(tp->t_flags2 & TF2_HPTS_CPU_SET)) {
                tp->t_hpts_cpu = hpts_cpuid(tp, &failed);
                if (failed == 0)
                        tp->t_flags2 |= TF2_HPTS_CPU_SET;
        }
        HPTS_UNLOCK(hpts);
}

static struct tcp_hpts_entry *
tcp_choose_hpts_to_run(void)
{
        int i, oldest_idx, start, end;
        uint32_t cts, time_since_ran, calc;

        cts = tcp_get_usecs(NULL);
        time_since_ran = 0;
        /* Default is all one group */
        start = 0;
        end = tcp_pace.rp_num_hptss;
        /*
         * If we have more than one L3 group figure out which one
         * this CPU is in.
         */
        if (tcp_pace.grp_cnt > 1) {
                for (i = 0; i < tcp_pace.grp_cnt; i++) {
                        if (CPU_ISSET(curcpu, &tcp_pace.grps[i]->cg_mask)) {
                                start = tcp_pace.grps[i]->cg_first;
                                end = (tcp_pace.grps[i]->cg_last + 1);
                                break;
                        }
                }
        }
        oldest_idx = -1;
        for (i = start; i < end; i++) {
                if (TSTMP_GT(cts, tcp_pace.cts_last_ran[i]))
                        calc = cts - tcp_pace.cts_last_ran[i];
                else
                        calc = 0;
                if (calc > time_since_ran) {
                        oldest_idx = i;
                        time_since_ran = calc;
                }
        }
        if (oldest_idx >= 0)
                return(tcp_pace.rp_ent[oldest_idx]);
        else
                return(tcp_pace.rp_ent[(curcpu % tcp_pace.rp_num_hptss)]);
}

static void
__tcp_run_hpts(void)
{
        struct epoch_tracker et;
        struct tcp_hpts_entry *hpts;
        int ticks_ran;

        hpts = tcp_choose_hpts_to_run();

        if (hpts->p_hpts_active) {
                /* Already active */
                return;
        }
        if (!HPTS_TRYLOCK(hpts)) {
                /* Someone else got the lock */
                return;
        }
        NET_EPOCH_ENTER(et);
        if (hpts->p_hpts_active)
                goto out_with_mtx;
        hpts->syscall_cnt++;
        counter_u64_add(hpts_direct_call, 1);
        hpts->p_hpts_active = 1;
        ticks_ran = tcp_hptsi(hpts, false);
        /* We may want to adjust the sleep values here */
        if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                if (ticks_ran > ticks_indicate_less_sleep) {
                        struct timeval tv;
                        sbintime_t sb;

                        hpts->p_mysleep.tv_usec /= 2;
                        if (hpts->p_mysleep.tv_usec < dynamic_min_sleep)
                                hpts->p_mysleep.tv_usec = dynamic_min_sleep;
                        /* Reschedule with new to value */
                        tcp_hpts_set_max_sleep(hpts, 0);
                        tv.tv_sec = 0;
                        tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
                        /* Validate its in the right ranges */
                        if (tv.tv_usec < hpts->p_mysleep.tv_usec) {
                                hpts->overidden_sleep = tv.tv_usec;
                                tv.tv_usec = hpts->p_mysleep.tv_usec;
                        } else if (tv.tv_usec > dynamic_max_sleep) {
                                /* Lets not let sleep get above this value */
                                hpts->overidden_sleep = tv.tv_usec;
                                tv.tv_usec = dynamic_max_sleep;
                        }
                        /*
                         * In this mode the timer is a backstop to
                         * all the userret/lro_flushes so we use
                         * the dynamic value and set the on_min_sleep
                         * flag so we will not be awoken.
                         */
                        sb = tvtosbt(tv);
                        /* Store off to make visible the actual sleep time */
                        hpts->sleeping = tv.tv_usec;
                        callout_reset_sbt_on(&hpts->co, sb, 0,
                                             hpts_timeout_swi, hpts, hpts->p_cpu,
                                             (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
                } else if (ticks_ran < ticks_indicate_more_sleep) {
                        /* For the further sleep, don't reschedule  hpts */
                        hpts->p_mysleep.tv_usec *= 2;
                        if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                }
                hpts->p_on_min_sleep = 1;
        }
        hpts->p_hpts_active = 0;
out_with_mtx:
        HPTS_UNLOCK(hpts);
        NET_EPOCH_EXIT(et);
}

static void
tcp_hpts_thread(void *ctx)
{
        struct tcp_hpts_entry *hpts;
        struct epoch_tracker et;
        struct timeval tv;
        sbintime_t sb;
        int ticks_ran;

        hpts = (struct tcp_hpts_entry *)ctx;
        HPTS_LOCK(hpts);
        if (hpts->p_direct_wake) {
                /* Signaled by input or output with low occupancy count. */
                callout_stop(&hpts->co);
                counter_u64_add(hpts_direct_awakening, 1);
        } else {
                /* Timed out, the normal case. */
                counter_u64_add(hpts_wake_timeout, 1);
                if (callout_pending(&hpts->co) ||
                    !callout_active(&hpts->co)) {
                        HPTS_UNLOCK(hpts);
                        return;
                }
        }
        callout_deactivate(&hpts->co);
        hpts->p_hpts_wake_scheduled = 0;
        NET_EPOCH_ENTER(et);
        if (hpts->p_hpts_active) {
                /*
                 * We are active already. This means that a syscall
                 * trap or LRO is running in behalf of hpts. In that case
                 * we need to double our timeout since there seems to be
                 * enough activity in the system that we don't need to
                 * run as often (if we were not directly woken).
                 */
                tv.tv_sec = 0;
                if (hpts->p_direct_wake == 0) {
                        counter_u64_add(hpts_back_tosleep, 1);
                        if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                                hpts->p_mysleep.tv_usec *= 2;
                                if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                        hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                                tv.tv_usec = hpts->p_mysleep.tv_usec;
                                hpts->p_on_min_sleep = 1;
                        } else {
                                /*
                                 * Here we have low count on the wheel, but
                                 * somehow we still collided with one of the
                                 * connections. Lets go back to sleep for a
                                 * min sleep time, but clear the flag so we
                                 * can be awoken by insert.
                                 */
                                hpts->p_on_min_sleep = 0;
                                tv.tv_usec = tcp_min_hptsi_time;
                        }
                } else {
                        /*
                         * Directly woken most likely to reset the
                         * callout time.
                         */
                        tv.tv_usec = hpts->p_mysleep.tv_usec;
                }
                goto back_to_sleep;
        }
        hpts->sleeping = 0;
        hpts->p_hpts_active = 1;
        ticks_ran = tcp_hptsi(hpts, true);
        tv.tv_sec = 0;
        tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
        if ((hpts->p_on_queue_cnt > conn_cnt_thresh) && (hpts->hit_callout_thresh == 0)) {
                hpts->hit_callout_thresh = 1;
                atomic_add_int(&hpts_that_need_softclock, 1);
        } else if ((hpts->p_on_queue_cnt <= conn_cnt_thresh) && (hpts->hit_callout_thresh == 1)) {
                hpts->hit_callout_thresh = 0;
                atomic_subtract_int(&hpts_that_need_softclock, 1);
        }
        if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                if(hpts->p_direct_wake == 0) {
                        /*
                         * Only adjust sleep time if we were
                         * called from the callout i.e. direct_wake == 0.
                         */
                        if (ticks_ran < ticks_indicate_more_sleep) {
                                hpts->p_mysleep.tv_usec *= 2;
                                if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                        hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                        } else if (ticks_ran > ticks_indicate_less_sleep) {
                                hpts->p_mysleep.tv_usec /= 2;
                                if (hpts->p_mysleep.tv_usec < dynamic_min_sleep)
                                        hpts->p_mysleep.tv_usec = dynamic_min_sleep;
                        }
                }
                if (tv.tv_usec < hpts->p_mysleep.tv_usec) {
                        hpts->overidden_sleep = tv.tv_usec;
                        tv.tv_usec = hpts->p_mysleep.tv_usec;
                } else if (tv.tv_usec > dynamic_max_sleep) {
                        /* Lets not let sleep get above this value */
                        hpts->overidden_sleep = tv.tv_usec;
                        tv.tv_usec = dynamic_max_sleep;
                }
                /*
                 * In this mode the timer is a backstop to
                 * all the userret/lro_flushes so we use
                 * the dynamic value and set the on_min_sleep
                 * flag so we will not be awoken.
                 */
                hpts->p_on_min_sleep = 1;
        } else if (hpts->p_on_queue_cnt == 0)  {
                /*
                 * No one on the wheel, please wake us up
                 * if you insert on the wheel.
                 */
                hpts->p_on_min_sleep = 0;
                hpts->overidden_sleep = 0;
        } else {
                /*
                 * We hit here when we have a low number of
                 * clients on the wheel (our else clause).
                 * We may need to go on min sleep, if we set
                 * the flag we will not be awoken if someone
                 * is inserted ahead of us. Clearing the flag
                 * means we can be awoken. This is "old mode"
                 * where the timer is what runs hpts mainly.
                 */
                if (tv.tv_usec < tcp_min_hptsi_time) {
                        /*
                         * Yes on min sleep, which means
                         * we cannot be awoken.
                         */
                        hpts->overidden_sleep = tv.tv_usec;
                        tv.tv_usec = tcp_min_hptsi_time;
                        hpts->p_on_min_sleep = 1;
                } else {
                        /* Clear the min sleep flag */
                        hpts->overidden_sleep = 0;
                        hpts->p_on_min_sleep = 0;
                }
        }
        HPTS_MTX_ASSERT(hpts);
        hpts->p_hpts_active = 0;
back_to_sleep:
        hpts->p_direct_wake = 0;
        sb = tvtosbt(tv);
        /* Store off to make visible the actual sleep time */
        hpts->sleeping = tv.tv_usec;
        callout_reset_sbt_on(&hpts->co, sb, 0,
                             hpts_timeout_swi, hpts, hpts->p_cpu,
                             (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
        NET_EPOCH_EXIT(et);
        HPTS_UNLOCK(hpts);
}

#undef  timersub

static int32_t
hpts_count_level(struct cpu_group *cg)
{
        int32_t count_l3, i;

        count_l3 = 0;
        if (cg->cg_level == CG_SHARE_L3)
                count_l3++;
        /* Walk all the children looking for L3 */
        for (i = 0; i < cg->cg_children; i++) {
                count_l3 += hpts_count_level(&cg->cg_child[i]);
        }
        return (count_l3);
}

static void
hpts_gather_grps(struct cpu_group **grps, int32_t *at, int32_t max, struct cpu_group *cg)
{
        int32_t idx, i;

        idx = *at;
        if (cg->cg_level == CG_SHARE_L3) {
                grps[idx] = cg;
                idx++;
                if (idx == max) {
                        *at = idx;
                        return;
                }
        }
        *at = idx;
        /* Walk all the children looking for L3 */
        for (i = 0; i < cg->cg_children; i++) {
                hpts_gather_grps(grps, at, max, &cg->cg_child[i]);
        }
}

static void
tcp_hpts_mod_load(void)
{
        struct cpu_group *cpu_top;
        int32_t error __diagused;
        int32_t i, j, bound = 0, created = 0;
        size_t sz, asz;
        struct timeval tv;
        sbintime_t sb;
        struct tcp_hpts_entry *hpts;
        struct pcpu *pc;
        char unit[16];
        uint32_t ncpus = mp_ncpus ? mp_ncpus : MAXCPU;
        int count, domain;

#ifdef SMP
        cpu_top = smp_topo();
#else
        cpu_top = NULL;
#endif
        tcp_pace.rp_num_hptss = ncpus;
        hpts_hopelessly_behind = counter_u64_alloc(M_WAITOK);
        hpts_loops = counter_u64_alloc(M_WAITOK);
        back_tosleep = counter_u64_alloc(M_WAITOK);
        combined_wheel_wrap = counter_u64_alloc(M_WAITOK);
        wheel_wrap = counter_u64_alloc(M_WAITOK);
        hpts_wake_timeout = counter_u64_alloc(M_WAITOK);
        hpts_direct_awakening = counter_u64_alloc(M_WAITOK);
        hpts_back_tosleep = counter_u64_alloc(M_WAITOK);
        hpts_direct_call = counter_u64_alloc(M_WAITOK);
        cpu_uses_flowid = counter_u64_alloc(M_WAITOK);
        cpu_uses_random = counter_u64_alloc(M_WAITOK);

        sz = (tcp_pace.rp_num_hptss * sizeof(struct tcp_hpts_entry *));
        tcp_pace.rp_ent = malloc(sz, M_TCPHPTS, M_WAITOK | M_ZERO);
        sz = (sizeof(uint32_t) * tcp_pace.rp_num_hptss);
        tcp_pace.cts_last_ran = malloc(sz, M_TCPHPTS, M_WAITOK);
        tcp_pace.grp_cnt = 0;
        if (cpu_top == NULL) {
                tcp_pace.grp_cnt = 1;
        } else {
                /* Find out how many cache level 3 domains we have */
                count = 0;
                tcp_pace.grp_cnt = hpts_count_level(cpu_top);
                if (tcp_pace.grp_cnt == 0) {
                        tcp_pace.grp_cnt = 1;
                }
                sz = (tcp_pace.grp_cnt * sizeof(struct cpu_group *));
                tcp_pace.grps = malloc(sz, M_TCPHPTS, M_WAITOK);
                /* Now populate the groups */
                if (tcp_pace.grp_cnt == 1) {
                        /*
                         * All we need is the top level all cpu's are in
                         * the same cache so when we use grp[0]->cg_mask
                         * with the cg_first <-> cg_last it will include
                         * all cpu's in it. The level here is probably
                         * zero which is ok.
                         */
                        tcp_pace.grps[0] = cpu_top;
                } else {
                        /*
                         * Here we must find all the level three cache domains
                         * and setup our pointers to them.
                         */
                        count = 0;
                        hpts_gather_grps(tcp_pace.grps, &count, tcp_pace.grp_cnt, cpu_top);
                }
        }
        asz = sizeof(struct hptsh) * NUM_OF_HPTSI_SLOTS;
        for (i = 0; i < tcp_pace.rp_num_hptss; i++) {
                tcp_pace.rp_ent[i] = malloc(sizeof(struct tcp_hpts_entry),
                    M_TCPHPTS, M_WAITOK | M_ZERO);
                tcp_pace.rp_ent[i]->p_hptss = malloc(asz, M_TCPHPTS, M_WAITOK);
                hpts = tcp_pace.rp_ent[i];
                /*
                 * Init all the hpts structures that are not specifically
                 * zero'd by the allocations. Also lets attach them to the
                 * appropriate sysctl block as well.
                 */
                mtx_init(&hpts->p_mtx, "tcp_hpts_lck",
                    "hpts", MTX_DEF | MTX_DUPOK);
                for (j = 0; j < NUM_OF_HPTSI_SLOTS; j++) {
                        TAILQ_INIT(&hpts->p_hptss[j].head);
                        hpts->p_hptss[j].count = 0;
                        hpts->p_hptss[j].gencnt = 0;
                }
                sysctl_ctx_init(&hpts->hpts_ctx);
                sprintf(unit, "%d", i);
                hpts->hpts_root = SYSCTL_ADD_NODE(&hpts->hpts_ctx,
                    SYSCTL_STATIC_CHILDREN(_net_inet_tcp_hpts),
                    OID_AUTO,
                    unit,
                    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                    "");
                SYSCTL_ADD_INT(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "out_qcnt", CTLFLAG_RD,
                    &hpts->p_on_queue_cnt, 0,
                    "Count TCB's awaiting output processing");
                SYSCTL_ADD_U16(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "active", CTLFLAG_RD,
                    &hpts->p_hpts_active, 0,
                    "Is the hpts active");
                SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "curslot", CTLFLAG_RD,
                    &hpts->p_cur_slot, 0,
                    "What the current running pacers goal");
                SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "runtick", CTLFLAG_RD,
                    &hpts->p_runningslot, 0,
                    "What the running pacers current slot is");
                SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "curtick", CTLFLAG_RD,
                    &hpts->p_curtick, 0,
                    "What the running pacers last tick mapped to the wheel was");
                SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "lastran", CTLFLAG_RD,
                    &tcp_pace.cts_last_ran[i], 0,
                    "The last usec tick that this hpts ran");
                SYSCTL_ADD_LONG(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "cur_min_sleep", CTLFLAG_RD,
                    &hpts->p_mysleep.tv_usec,
                    "What the running pacers is using for p_mysleep.tv_usec");
                SYSCTL_ADD_U64(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "now_sleeping", CTLFLAG_RD,
                    &hpts->sleeping, 0,
                    "What the running pacers is actually sleeping for");
                SYSCTL_ADD_U64(&hpts->hpts_ctx,
                    SYSCTL_CHILDREN(hpts->hpts_root),
                    OID_AUTO, "syscall_cnt", CTLFLAG_RD,
                    &hpts->syscall_cnt, 0,
                    "How many times we had syscalls on this hpts");

                hpts->p_hpts_sleep_time = hpts_sleep_max;
                hpts->p_num = i;
                hpts->p_curtick = tcp_gethptstick(&tv);
                tcp_pace.cts_last_ran[i] = tcp_tv_to_usectick(&tv);
                hpts->p_prev_slot = hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
                hpts->p_cpu = 0xffff;
                hpts->p_nxt_slot = hpts_slot(hpts->p_cur_slot, 1);
                callout_init(&hpts->co, 1);
        }
        /* Don't try to bind to NUMA domains if we don't have any */
        if (vm_ndomains == 1 && tcp_bind_threads == 2)
                tcp_bind_threads = 0;

        /*
         * Now lets start ithreads to handle the hptss.
         */
        for (i = 0; i < tcp_pace.rp_num_hptss; i++) {
                hpts = tcp_pace.rp_ent[i];
                hpts->p_cpu = i;

                error = swi_add(&hpts->ie, "hpts",
                    tcp_hpts_thread, (void *)hpts,
                    SWI_NET, INTR_MPSAFE, &hpts->ie_cookie);
                KASSERT(error == 0,
                        ("Can't add hpts:%p i:%d err:%d",
                         hpts, i, error));
                created++;
                hpts->p_mysleep.tv_sec = 0;
                hpts->p_mysleep.tv_usec = tcp_min_hptsi_time;
                if (tcp_bind_threads == 1) {
                        if (intr_event_bind(hpts->ie, i) == 0)
                                bound++;
                } else if (tcp_bind_threads == 2) {
                        /* Find the group for this CPU (i) and bind into it */
                        for (j = 0; j < tcp_pace.grp_cnt; j++) {
                                if (CPU_ISSET(i, &tcp_pace.grps[j]->cg_mask)) {
                                        if (intr_event_bind_ithread_cpuset(hpts->ie,
                                                &tcp_pace.grps[j]->cg_mask) == 0) {
                                                bound++;
                                                pc = pcpu_find(i);
                                                domain = pc->pc_domain;
                                                count = hpts_domains[domain].count;
                                                hpts_domains[domain].cpu[count] = i;
                                                hpts_domains[domain].count++;
                                                break;
                                        }
                                }
                        }
                }
                tv.tv_sec = 0;
                tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
                hpts->sleeping = tv.tv_usec;
                sb = tvtosbt(tv);
                callout_reset_sbt_on(&hpts->co, sb, 0,
                                     hpts_timeout_swi, hpts, hpts->p_cpu,
                                     (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
        }
        /*
         * If we somehow have an empty domain, fall back to choosing
         * among all htps threads.
         */
        for (i = 0; i < vm_ndomains; i++) {
                if (hpts_domains[i].count == 0) {
                        tcp_bind_threads = 0;
                        break;
                }
        }
        tcp_hpts_softclock = __tcp_run_hpts;
        tcp_lro_hpts_init();
        printf("TCP Hpts created %d swi interrupt threads and bound %d to %s\n",
            created, bound,
            tcp_bind_threads == 2 ? "NUMA domains" : "cpus");
}

static void
tcp_hpts_mod_unload(void)
{
        int rv __diagused;

        tcp_lro_hpts_uninit();
        atomic_store_ptr(&tcp_hpts_softclock, NULL);

        for (int i = 0; i < tcp_pace.rp_num_hptss; i++) {
                struct tcp_hpts_entry *hpts = tcp_pace.rp_ent[i];

                rv = callout_drain(&hpts->co);
                MPASS(rv != 0);

                rv = swi_remove(hpts->ie_cookie);
                MPASS(rv == 0);

                rv = sysctl_ctx_free(&hpts->hpts_ctx);
                MPASS(rv == 0);

                mtx_destroy(&hpts->p_mtx);
                free(hpts->p_hptss, M_TCPHPTS);
                free(hpts, M_TCPHPTS);
        }

        free(tcp_pace.rp_ent, M_TCPHPTS);
        free(tcp_pace.cts_last_ran, M_TCPHPTS);
#ifdef SMP
        free(tcp_pace.grps, M_TCPHPTS);
#endif

        counter_u64_free(hpts_hopelessly_behind);
        counter_u64_free(hpts_loops);
        counter_u64_free(back_tosleep);
        counter_u64_free(combined_wheel_wrap);
        counter_u64_free(wheel_wrap);
        counter_u64_free(hpts_wake_timeout);
        counter_u64_free(hpts_direct_awakening);
        counter_u64_free(hpts_back_tosleep);
        counter_u64_free(hpts_direct_call);
        counter_u64_free(cpu_uses_flowid);
        counter_u64_free(cpu_uses_random);
}

static int
tcp_hpts_modevent(module_t mod, int what, void *arg)
{

        switch (what) {
        case MOD_LOAD:
                tcp_hpts_mod_load();
                return (0);
        case MOD_QUIESCE:
                /*
                 * Since we are a dependency of TCP stack modules, they should
                 * already be unloaded, and the HPTS ring is empty.  However,
                 * function pointer manipulations aren't 100% safe.  Although,
                 * tcp_hpts_mod_unload() use atomic(9) the userret() doesn't.
                 * Thus, allow only forced unload of HPTS.
                 */
                return (EBUSY);
        case MOD_UNLOAD:
                tcp_hpts_mod_unload();
                return (0);
        default:
                return (EINVAL);
        };
}

static moduledata_t tcp_hpts_module = {
        .name = "tcphpts",
        .evhand = tcp_hpts_modevent,
};

DECLARE_MODULE(tcphpts, tcp_hpts_module, SI_SUB_SOFTINTR, SI_ORDER_ANY);
MODULE_VERSION(tcphpts, 1);