linux/samples/bpf/offwaketime_kern.c
Daniel Borkmann 02413cabd6 bpf, samples: don't zero data when not needed
Remove the zero initialization in the sample programs where appropriate.
Note that this is an optimization which is now possible, old programs
still doing the zero initialization are just fine as well. Also, make
sure we don't have padding issues when we don't memset() the entire
struct anymore.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-14 21:40:42 -04:00

152 lines
3.5 KiB
C

/* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"
#include <uapi/linux/ptrace.h>
#include <uapi/linux/perf_event.h>
#include <linux/version.h>
#include <linux/sched.h>
#define _(P) ({typeof(P) val; bpf_probe_read(&val, sizeof(val), &P); val;})
#define MINBLOCK_US 1
struct key_t {
char waker[TASK_COMM_LEN];
char target[TASK_COMM_LEN];
u32 wret;
u32 tret;
};
struct bpf_map_def SEC("maps") counts = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(struct key_t),
.value_size = sizeof(u64),
.max_entries = 10000,
};
struct bpf_map_def SEC("maps") start = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(u32),
.value_size = sizeof(u64),
.max_entries = 10000,
};
struct wokeby_t {
char name[TASK_COMM_LEN];
u32 ret;
};
struct bpf_map_def SEC("maps") wokeby = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(u32),
.value_size = sizeof(struct wokeby_t),
.max_entries = 10000,
};
struct bpf_map_def SEC("maps") stackmap = {
.type = BPF_MAP_TYPE_STACK_TRACE,
.key_size = sizeof(u32),
.value_size = PERF_MAX_STACK_DEPTH * sizeof(u64),
.max_entries = 10000,
};
#define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
SEC("kprobe/try_to_wake_up")
int waker(struct pt_regs *ctx)
{
struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
struct wokeby_t woke;
u32 pid;
pid = _(p->pid);
bpf_get_current_comm(&woke.name, sizeof(woke.name));
woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
return 0;
}
static inline int update_counts(void *ctx, u32 pid, u64 delta)
{
struct wokeby_t *woke;
u64 zero = 0, *val;
struct key_t key;
__builtin_memset(&key.waker, 0, sizeof(key.waker));
bpf_get_current_comm(&key.target, sizeof(key.target));
key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
key.wret = 0;
woke = bpf_map_lookup_elem(&wokeby, &pid);
if (woke) {
key.wret = woke->ret;
__builtin_memcpy(&key.waker, woke->name, sizeof(key.waker));
bpf_map_delete_elem(&wokeby, &pid);
}
val = bpf_map_lookup_elem(&counts, &key);
if (!val) {
bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
val = bpf_map_lookup_elem(&counts, &key);
if (!val)
return 0;
}
(*val) += delta;
return 0;
}
#if 1
/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
struct sched_switch_args {
unsigned long long pad;
char prev_comm[16];
int prev_pid;
int prev_prio;
long long prev_state;
char next_comm[16];
int next_pid;
int next_prio;
};
SEC("tracepoint/sched/sched_switch")
int oncpu(struct sched_switch_args *ctx)
{
/* record previous thread sleep time */
u32 pid = ctx->prev_pid;
#else
SEC("kprobe/finish_task_switch")
int oncpu(struct pt_regs *ctx)
{
struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
/* record previous thread sleep time */
u32 pid = _(p->pid);
#endif
u64 delta, ts, *tsp;
ts = bpf_ktime_get_ns();
bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
/* calculate current thread's delta time */
pid = bpf_get_current_pid_tgid();
tsp = bpf_map_lookup_elem(&start, &pid);
if (!tsp)
/* missed start or filtered */
return 0;
delta = bpf_ktime_get_ns() - *tsp;
bpf_map_delete_elem(&start, &pid);
delta = delta / 1000;
if (delta < MINBLOCK_US)
return 0;
return update_counts(ctx, pid, delta);
}
char _license[] SEC("license") = "GPL";
u32 _version SEC("version") = LINUX_VERSION_CODE;