tools/bpf/runqslower/runqslower.bpf.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2019 Facebook
   3 #include "vmlinux.h"
   4 #include <bpf/bpf_helpers.h>
   5 #include "runqslower.h"
   6
   7 #define TASK_RUNNING 0
   8 #define BPF_F_CURRENT_CPU 0xffffffffULL
   9
  10 const volatile __u64 min_us = 0;
  11 const volatile pid_t targ_pid = 0;
  12
  13 struct {
  14         __uint(type, BPF_MAP_TYPE_HASH);
  15         __uint(max_entries, 10240);
  16         __type(key, u32);
  17         __type(value, u64);
  18 } start SEC(".maps");
  19
  20 struct {
  21         __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
  22         __uint(key_size, sizeof(u32));
  23         __uint(value_size, sizeof(u32));
  24 } events SEC(".maps");
  25
  26 /* record enqueue timestamp */
  27 __always_inline
  28 static int trace_enqueue(u32 tgid, u32 pid)
  29 {
  30         u64 ts;
  31
  32         if (!pid || (targ_pid && targ_pid != pid))
  33                 return 0;
  34
  35         ts = bpf_ktime_get_ns();
  36         bpf_map_update_elem(&start, &pid, &ts, 0);
  37         return 0;
  38 }
  39
  40 SEC("tp_btf/sched_wakeup")
  41 int handle__sched_wakeup(u64 *ctx)
  42 {
  43         /* TP_PROTO(struct task_struct *p) */
  44         struct task_struct *p = (void *)ctx[0];
  45
  46         return trace_enqueue(p->tgid, p->pid);
  47 }
  48
  49 SEC("tp_btf/sched_wakeup_new")
  50 int handle__sched_wakeup_new(u64 *ctx)
  51 {
  52         /* TP_PROTO(struct task_struct *p) */
  53         struct task_struct *p = (void *)ctx[0];
  54
  55         return trace_enqueue(p->tgid, p->pid);
  56 }
  57
  58 SEC("tp_btf/sched_switch")
  59 int handle__sched_switch(u64 *ctx)
  60 {
  61         /* TP_PROTO(bool preempt, struct task_struct *prev,
  62          *          struct task_struct *next)
  63          */
  64         struct task_struct *prev = (struct task_struct *)ctx[1];
  65         struct task_struct *next = (struct task_struct *)ctx[2];
  66         struct event event = {};
  67         u64 *tsp, delta_us;
  68         long state;
  69         u32 pid;
  70
  71         /* ivcsw: treat like an enqueue event and store timestamp */
  72         if (prev->state == TASK_RUNNING)
  73                 trace_enqueue(prev->tgid, prev->pid);
  74
  75         pid = next->pid;
  76
  77         /* fetch timestamp and calculate delta */
  78         tsp = bpf_map_lookup_elem(&start, &pid);
  79         if (!tsp)
  80                 return 0;   /* missed enqueue */
  81
  82         delta_us = (bpf_ktime_get_ns() - *tsp) / 1000;
  83         if (min_us && delta_us <= min_us)
  84                 return 0;
  85
  86         event.pid = pid;
  87         event.delta_us = delta_us;
  88         bpf_get_current_comm(&event.task, sizeof(event.task));
  89
  90         /* output */
  91         bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,
  92                               &event, sizeof(event));
  93
  94         bpf_map_delete_elem(&start, &pid);
  95         return 0;
  96 }
  97
  98 char LICENSE[] SEC("license") = "GPL";