Linux 5.1.15

[linux/fpc-iii.git] / tools / perf / bench / epoll-wait.c

// SPDX-License-Identifier: GPL-2.0
#ifdef HAVE_EVENTFD
/*
 * Copyright (C) 2018 Davidlohr Bueso.
 *
 * This program benchmarks concurrent epoll_wait(2) monitoring multiple
 * file descriptors under one or two load balancing models. The first,
 * and default, is the single/combined queueing (which refers to a single
 * epoll instance for N worker threads):
 *
 *                          |---> [worker A]
 *                          |---> [worker B]
 *        [combined queue]  .---> [worker C]
 *                          |---> [worker D]
 *                          |---> [worker E]
 *
 * While the second model, enabled via --multiq option, uses multiple
 * queueing (which refers to one epoll instance per worker). For example,
 * short lived tcp connections in a high throughput httpd server will
 * ditribute the accept()'ing  connections across CPUs. In this case each
 * worker does a limited  amount of processing.
 *
 *             [queue A]  ---> [worker]
 *             [queue B]  ---> [worker]
 *             [queue C]  ---> [worker]
 *             [queue D]  ---> [worker]
 *             [queue E]  ---> [worker]
 *
 * Naturally, the single queue will enforce more concurrency on the epoll
 * instance, and can therefore scale poorly compared to multiple queues.
 * However, this is a benchmark raw data and must be taken with a grain of
 * salt when choosing how to make use of sys_epoll.

 * Each thread has a number of private, nonblocking file descriptors,
 * referred to as fdmap. A writer thread will constantly be writing to
 * the fdmaps of all threads, minimizing each threads's chances of
 * epoll_wait not finding any ready read events and blocking as this
 * is not what we want to stress. The size of the fdmap can be adjusted
 * by the user; enlarging the value will increase the chances of
 * epoll_wait(2) blocking as the lineal writer thread will take "longer",
 * at least at a high level.
 *
 * Note that because fds are private to each thread, this workload does
 * not stress scenarios where multiple tasks are awoken per ready IO; ie:
 * EPOLLEXCLUSIVE semantics.
 *
 * The end result/metric is throughput: number of ops/second where an
 * operation consists of:
 *
 *   epoll_wait(2) + [others]
 *
 *        ... where [others] is the cost of re-adding the fd (EPOLLET),
 *            or rearming it (EPOLLONESHOT).
 *
 *
 * The purpose of this is program is that it be useful for measuring
 * kernel related changes to the sys_epoll, and not comparing different
 * IO polling methods, for example. Hence everything is very adhoc and
 * outputs raw microbenchmark numbers. Also this uses eventfd, similar
 * tools tend to use pipes or sockets, but the result is the same.
 */

/* For the CLR_() macros */
#include <string.h>
#include <pthread.h>

#include <errno.h>
#include <inttypes.h>
#include <signal.h>
#include <stdlib.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/types.h>

#include "../util/stat.h"
#include <subcmd/parse-options.h>
#include "bench.h"
#include "cpumap.h"

#include <err.h>

#define printinfo(fmt, arg...) \
        do { if (__verbose) { printf(fmt, ## arg); fflush(stdout); } } while (0)

static unsigned int nthreads = 0;
static unsigned int nsecs    = 8;
struct timeval start, end, runtime;
static bool wdone, done, __verbose, randomize, nonblocking;

/*
 * epoll related shared variables.
 */

/* Maximum number of nesting allowed inside epoll sets */
#define EPOLL_MAXNESTS 4

static int epollfd;
static int *epollfdp;
static bool noaffinity;
static unsigned int nested = 0;
static bool et; /* edge-trigger */
static bool oneshot;
static bool multiq; /* use an epoll instance per thread */

/* amount of fds to monitor, per thread */
static unsigned int nfds = 64;

static pthread_mutex_t thread_lock;
static unsigned int threads_starting;
static struct stats throughput_stats;
static pthread_cond_t thread_parent, thread_worker;

struct worker {
        int tid;
        int epollfd; /* for --multiq */
        pthread_t thread;
        unsigned long ops;
        int *fdmap;
};

static const struct option options[] = {
        /* general benchmark options */
        OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
        OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds)"),
        OPT_UINTEGER('f', "nfds",    &nfds,  "Specify amount of file descriptors to monitor for each thread"),
        OPT_BOOLEAN( 'n', "noaffinity",  &noaffinity,   "Disables CPU affinity"),
        OPT_BOOLEAN('R', "randomize", &randomize,   "Enable random write behaviour (default is lineal)"),
        OPT_BOOLEAN( 'v', "verbose", &__verbose, "Verbose mode"),

        /* epoll specific options */
        OPT_BOOLEAN( 'm', "multiq",  &multiq,   "Use multiple epoll instances (one per thread)"),
        OPT_BOOLEAN( 'B', "nonblocking", &nonblocking, "Nonblocking epoll_wait(2) behaviour"),
        OPT_UINTEGER( 'N', "nested",  &nested,   "Nesting level epoll hierarchy (default is 0, no nesting)"),
        OPT_BOOLEAN( 'S', "oneshot",  &oneshot,   "Use EPOLLONESHOT semantics"),
        OPT_BOOLEAN( 'E', "edge",  &et,   "Use Edge-triggered interface (default is LT)"),

        OPT_END()
};

static const char * const bench_epoll_wait_usage[] = {
        "perf bench epoll wait <options>",
        NULL
};


/*
 * Arrange the N elements of ARRAY in random order.
 * Only effective if N is much smaller than RAND_MAX;
 * if this may not be the case, use a better random
 * number generator. -- Ben Pfaff.
 */
static void shuffle(void *array, size_t n, size_t size)
{
        char *carray = array;
        void *aux;
        size_t i;

        if (n <= 1)
                return;

        aux = calloc(1, size);
        if (!aux)
                err(EXIT_FAILURE, "calloc");

        for (i = 1; i < n; ++i) {
                size_t j =   i + rand() / (RAND_MAX / (n - i) + 1);
                j *= size;

                memcpy(aux, &carray[j], size);
                memcpy(&carray[j], &carray[i*size], size);
                memcpy(&carray[i*size], aux, size);
        }

        free(aux);
}


static void *workerfn(void *arg)
{
        int fd, ret, r;
        struct worker *w = (struct worker *) arg;
        unsigned long ops = w->ops;
        struct epoll_event ev;
        uint64_t val;
        int to = nonblocking? 0 : -1;
        int efd = multiq ? w->epollfd : epollfd;

        pthread_mutex_lock(&thread_lock);
        threads_starting--;
        if (!threads_starting)
                pthread_cond_signal(&thread_parent);
        pthread_cond_wait(&thread_worker, &thread_lock);
        pthread_mutex_unlock(&thread_lock);

        do {
                /*
                 * Block undefinitely waiting for the IN event.
                 * In order to stress the epoll_wait(2) syscall,
                 * call it event per event, instead of a larger
                 * batch (max)limit.
                 */
                do {
                        ret = epoll_wait(efd, &ev, 1, to);
                } while (ret < 0 && errno == EINTR);
                if (ret < 0)
                        err(EXIT_FAILURE, "epoll_wait");

                fd = ev.data.fd;

                do {
                        r = read(fd, &val, sizeof(val));
                } while (!done && (r < 0 && errno == EAGAIN));

                if (et) {
                        ev.events = EPOLLIN | EPOLLET;
                        ret = epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ev);
                }

                if (oneshot) {
                        /* rearm the file descriptor with a new event mask */
                        ev.events |= EPOLLIN | EPOLLONESHOT;
                        ret = epoll_ctl(efd, EPOLL_CTL_MOD, fd, &ev);
                }

                ops++;
        }  while (!done);

        if (multiq)
                close(w->epollfd);

        w->ops = ops;
        return NULL;
}

static void nest_epollfd(struct worker *w)
{
        unsigned int i;
        struct epoll_event ev;
        int efd = multiq ? w->epollfd : epollfd;

        if (nested > EPOLL_MAXNESTS)
                nested = EPOLL_MAXNESTS;

        epollfdp = calloc(nested, sizeof(*epollfdp));
        if (!epollfdp)
                err(EXIT_FAILURE, "calloc");

        for (i = 0; i < nested; i++) {
                epollfdp[i] = epoll_create(1);
                if (epollfdp[i] < 0)
                        err(EXIT_FAILURE, "epoll_create");
        }

        ev.events = EPOLLHUP; /* anything */
        ev.data.u64 = i; /* any number */

        for (i = nested - 1; i; i--) {
                if (epoll_ctl(epollfdp[i - 1], EPOLL_CTL_ADD,
                              epollfdp[i], &ev) < 0)
                        err(EXIT_FAILURE, "epoll_ctl");
        }

        if (epoll_ctl(efd, EPOLL_CTL_ADD, *epollfdp, &ev) < 0)
                err(EXIT_FAILURE, "epoll_ctl");
}

static void toggle_done(int sig __maybe_unused,
                        siginfo_t *info __maybe_unused,
                        void *uc __maybe_unused)
{
        /* inform all threads that we're done for the day */
        done = true;
        gettimeofday(&end, NULL);
        timersub(&end, &start, &runtime);
}

static void print_summary(void)
{
        unsigned long avg = avg_stats(&throughput_stats);
        double stddev = stddev_stats(&throughput_stats);

        printf("\nAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
               avg, rel_stddev_stats(stddev, avg),
               (int) runtime.tv_sec);
}

static int do_threads(struct worker *worker, struct cpu_map *cpu)
{
        pthread_attr_t thread_attr, *attrp = NULL;
        cpu_set_t cpuset;
        unsigned int i, j;
        int ret = 0, events = EPOLLIN;

        if (oneshot)
                events |= EPOLLONESHOT;
        if (et)
                events |= EPOLLET;

        printinfo("starting worker/consumer %sthreads%s\n",
                  noaffinity ?  "":"CPU affinity ",
                  nonblocking ? " (nonblocking)":"");
        if (!noaffinity)
                pthread_attr_init(&thread_attr);

        for (i = 0; i < nthreads; i++) {
                struct worker *w = &worker[i];

                if (multiq) {
                        w->epollfd = epoll_create(1);
                        if (w->epollfd < 0)
                                err(EXIT_FAILURE, "epoll_create");

                        if (nested)
                                nest_epollfd(w);
                }

                w->tid = i;
                w->fdmap = calloc(nfds, sizeof(int));
                if (!w->fdmap)
                        return 1;

                for (j = 0; j < nfds; j++) {
                        int efd = multiq ? w->epollfd : epollfd;
                        struct epoll_event ev;

                        w->fdmap[j] = eventfd(0, EFD_NONBLOCK);
                        if (w->fdmap[j] < 0)
                                err(EXIT_FAILURE, "eventfd");

                        ev.data.fd = w->fdmap[j];
                        ev.events = events;

                        ret = epoll_ctl(efd, EPOLL_CTL_ADD,
                                        w->fdmap[j], &ev);
                        if (ret < 0)
                                err(EXIT_FAILURE, "epoll_ctl");
                }

                if (!noaffinity) {
                        CPU_ZERO(&cpuset);
                        CPU_SET(cpu->map[i % cpu->nr], &cpuset);

                        ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset);
                        if (ret)
                                err(EXIT_FAILURE, "pthread_attr_setaffinity_np");

                        attrp = &thread_attr;
                }

                ret = pthread_create(&w->thread, attrp, workerfn,
                                     (void *)(struct worker *) w);
                if (ret)
                        err(EXIT_FAILURE, "pthread_create");
        }

        if (!noaffinity)
                pthread_attr_destroy(&thread_attr);

        return ret;
}

static void *writerfn(void *p)
{
        struct worker *worker = p;
        size_t i, j, iter;
        const uint64_t val = 1;
        ssize_t sz;
        struct timespec ts = { .tv_sec = 0,
                               .tv_nsec = 500 };

        printinfo("starting writer-thread: doing %s writes ...\n",
                  randomize? "random":"lineal");

        for (iter = 0; !wdone; iter++) {
                if (randomize) {
                        shuffle((void *)worker, nthreads, sizeof(*worker));
                }

                for (i = 0; i < nthreads; i++) {
                        struct worker *w = &worker[i];

                        if (randomize) {
                                shuffle((void *)w->fdmap, nfds, sizeof(int));
                        }

                        for (j = 0; j < nfds; j++) {
                                do {
                                        sz = write(w->fdmap[j], &val, sizeof(val));
                                } while (!wdone && (sz < 0 && errno == EAGAIN));
                        }
                }

                nanosleep(&ts, NULL);
        }

        printinfo("exiting writer-thread (total full-loops: %zd)\n", iter);
        return NULL;
}

static int cmpworker(const void *p1, const void *p2)
{

        struct worker *w1 = (struct worker *) p1;
        struct worker *w2 = (struct worker *) p2;
        return w1->tid > w2->tid;
}

int bench_epoll_wait(int argc, const char **argv)
{
        int ret = 0;
        struct sigaction act;
        unsigned int i;
        struct worker *worker = NULL;
        struct cpu_map *cpu;
        pthread_t wthread;
        struct rlimit rl, prevrl;

        argc = parse_options(argc, argv, options, bench_epoll_wait_usage, 0);
        if (argc) {
                usage_with_options(bench_epoll_wait_usage, options);
                exit(EXIT_FAILURE);
        }

        sigfillset(&act.sa_mask);
        act.sa_sigaction = toggle_done;
        sigaction(SIGINT, &act, NULL);

        cpu = cpu_map__new(NULL);
        if (!cpu)
                goto errmem;

        /* a single, main epoll instance */
        if (!multiq) {
                epollfd = epoll_create(1);
                if (epollfd < 0)
                        err(EXIT_FAILURE, "epoll_create");

                /*
                 * Deal with nested epolls, if any.
                 */
                if (nested)
                        nest_epollfd(NULL);
        }

        printinfo("Using %s queue model\n", multiq ? "multi" : "single");
        printinfo("Nesting level(s): %d\n", nested);

        /* default to the number of CPUs and leave one for the writer pthread */
        if (!nthreads)
                nthreads = cpu->nr - 1;

        worker = calloc(nthreads, sizeof(*worker));
        if (!worker) {
                goto errmem;
        }

        if (getrlimit(RLIMIT_NOFILE, &prevrl))
                err(EXIT_FAILURE, "getrlimit");
        rl.rlim_cur = rl.rlim_max = nfds * nthreads * 2 + 50;
        printinfo("Setting RLIMIT_NOFILE rlimit from %" PRIu64 " to: %" PRIu64 "\n",
                  (uint64_t)prevrl.rlim_max, (uint64_t)rl.rlim_max);
        if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
                err(EXIT_FAILURE, "setrlimit");

        printf("Run summary [PID %d]: %d threads monitoring%s on "
               "%d file-descriptors for %d secs.\n\n",
               getpid(), nthreads, oneshot ? " (EPOLLONESHOT semantics)": "", nfds, nsecs);

        init_stats(&throughput_stats);
        pthread_mutex_init(&thread_lock, NULL);
        pthread_cond_init(&thread_parent, NULL);
        pthread_cond_init(&thread_worker, NULL);

        threads_starting = nthreads;

        gettimeofday(&start, NULL);

        do_threads(worker, cpu);

        pthread_mutex_lock(&thread_lock);
        while (threads_starting)
                pthread_cond_wait(&thread_parent, &thread_lock);
        pthread_cond_broadcast(&thread_worker);
        pthread_mutex_unlock(&thread_lock);

        /*
         * At this point the workers should be blocked waiting for read events
         * to become ready. Launch the writer which will constantly be writing
         * to each thread's fdmap.
         */
        ret = pthread_create(&wthread, NULL, writerfn,
                             (void *)(struct worker *) worker);
        if (ret)
                err(EXIT_FAILURE, "pthread_create");

        sleep(nsecs);
        toggle_done(0, NULL, NULL);
        printinfo("main thread: toggling done\n");

        sleep(1); /* meh */
        wdone = true;
        ret = pthread_join(wthread, NULL);
        if (ret)
                err(EXIT_FAILURE, "pthread_join");

        /* cleanup & report results */
        pthread_cond_destroy(&thread_parent);
        pthread_cond_destroy(&thread_worker);
        pthread_mutex_destroy(&thread_lock);

        /* sort the array back before reporting */
        if (randomize)
                qsort(worker, nthreads, sizeof(struct worker), cmpworker);

        for (i = 0; i < nthreads; i++) {
                unsigned long t = worker[i].ops/runtime.tv_sec;

                update_stats(&throughput_stats, t);

                if (nfds == 1)
                        printf("[thread %2d] fdmap: %p [ %04ld ops/sec ]\n",
                               worker[i].tid, &worker[i].fdmap[0], t);
                else
                        printf("[thread %2d] fdmap: %p ... %p [ %04ld ops/sec ]\n",
                               worker[i].tid, &worker[i].fdmap[0],
                               &worker[i].fdmap[nfds-1], t);
        }

        print_summary();

        close(epollfd);
        return ret;
errmem:
        err(EXIT_FAILURE, "calloc");
}
#endif // HAVE_EVENTFD