samples/bpf/offwaketime_kern.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <uapi/linux/bpf.h>
   8 #include <uapi/linux/ptrace.h>
   9 #include <uapi/linux/perf_event.h>
  10 #include <linux/version.h>
  11 #include <linux/sched.h>
  12 #include <bpf/bpf_helpers.h>
  13 #include <bpf/bpf_tracing.h>
  14
  15 #define _(P)                                                                   \
  16         ({                                                                     \
  17                 typeof(P) val;                                                 \
  18                 bpf_probe_read_kernel(&val, sizeof(val), &(P));                \
  19                 val;                                                           \
  20         })
  21
  22 #define MINBLOCK_US     1
  23
  24 struct key_t {
  25         char waker[TASK_COMM_LEN];
  26         char target[TASK_COMM_LEN];
  27         u32 wret;
  28         u32 tret;
  29 };
  30
  31 struct {
  32         __uint(type, BPF_MAP_TYPE_HASH);
  33         __type(key, struct key_t);
  34         __type(value, u64);
  35         __uint(max_entries, 10000);
  36 } counts SEC(".maps");
  37
  38 struct {
  39         __uint(type, BPF_MAP_TYPE_HASH);
  40         __type(key, u32);
  41         __type(value, u64);
  42         __uint(max_entries, 10000);
  43 } start SEC(".maps");
  44
  45 struct wokeby_t {
  46         char name[TASK_COMM_LEN];
  47         u32 ret;
  48 };
  49
  50 struct {
  51         __uint(type, BPF_MAP_TYPE_HASH);
  52         __type(key, u32);
  53         __type(value, struct wokeby_t);
  54         __uint(max_entries, 10000);
  55 } wokeby SEC(".maps");
  56
  57 struct {
  58         __uint(type, BPF_MAP_TYPE_STACK_TRACE);
  59         __uint(key_size, sizeof(u32));
  60         __uint(value_size, PERF_MAX_STACK_DEPTH * sizeof(u64));
  61         __uint(max_entries, 10000);
  62 } stackmap SEC(".maps");
  63
  64 #define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
  65
  66 SEC("kprobe/try_to_wake_up")
  67 int waker(struct pt_regs *ctx)
  68 {
  69         struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
  70         struct wokeby_t woke;
  71         u32 pid;
  72
  73         pid = _(p->pid);
  74
  75         bpf_get_current_comm(&woke.name, sizeof(woke.name));
  76         woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
  77
  78         bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
  79         return 0;
  80 }
  81
  82 static inline int update_counts(void *ctx, u32 pid, u64 delta)
  83 {
  84         struct wokeby_t *woke;
  85         u64 zero = 0, *val;
  86         struct key_t key;
  87
  88         __builtin_memset(&key.waker, 0, sizeof(key.waker));
  89         bpf_get_current_comm(&key.target, sizeof(key.target));
  90         key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
  91         key.wret = 0;
  92
  93         woke = bpf_map_lookup_elem(&wokeby, &pid);
  94         if (woke) {
  95                 key.wret = woke->ret;
  96                 __builtin_memcpy(&key.waker, woke->name, sizeof(key.waker));
  97                 bpf_map_delete_elem(&wokeby, &pid);
  98         }
  99
 100         val = bpf_map_lookup_elem(&counts, &key);
 101         if (!val) {
 102                 bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
 103                 val = bpf_map_lookup_elem(&counts, &key);
 104                 if (!val)
 105                         return 0;
 106         }
 107         (*val) += delta;
 108         return 0;
 109 }
 110
 111 #if 1
 112 /* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
 113 struct sched_switch_args {
 114         unsigned long long pad;
 115         char prev_comm[16];
 116         int prev_pid;
 117         int prev_prio;
 118         long long prev_state;
 119         char next_comm[16];
 120         int next_pid;
 121         int next_prio;
 122 };
 123 SEC("tracepoint/sched/sched_switch")
 124 int oncpu(struct sched_switch_args *ctx)
 125 {
 126         /* record previous thread sleep time */
 127         u32 pid = ctx->prev_pid;
 128 #else
 129 SEC("kprobe/finish_task_switch")
 130 int oncpu(struct pt_regs *ctx)
 131 {
 132         struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
 133         /* record previous thread sleep time */
 134         u32 pid = _(p->pid);
 135 #endif
 136         u64 delta, ts, *tsp;
 137
 138         ts = bpf_ktime_get_ns();
 139         bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
 140
 141         /* calculate current thread's delta time */
 142         pid = bpf_get_current_pid_tgid();
 143         tsp = bpf_map_lookup_elem(&start, &pid);
 144         if (!tsp)
 145                 /* missed start or filtered */
 146                 return 0;
 147
 148         delta = bpf_ktime_get_ns() - *tsp;
 149         bpf_map_delete_elem(&start, &pid);
 150         delta = delta / 1000;
 151         if (delta < MINBLOCK_US)
 152                 return 0;
 153
 154         return update_counts(ctx, pid, delta);
 155 }
 156 char _license[] SEC("license") = "GPL";
 157 u32 _version SEC("version") = LINUX_VERSION_CODE;