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// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
// Copyright (c) 2021 Google
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
// This should be in sync with "util/ftrace.h"
#define NUM_BUCKET 22
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u64));
__uint(value_size, sizeof(__u64));
__uint(max_entries, 10000);
} functime SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u8));
__uint(max_entries, 1);
} cpu_filter SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u8));
__uint(max_entries, 1);
} task_filter SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u64));
__uint(max_entries, NUM_BUCKET);
} latency SEC(".maps");
int enabled = 0;
// stats
__s64 total;
__s64 count;
__s64 max;
__s64 min;
const volatile int has_cpu = 0;
const volatile int has_task = 0;
const volatile int use_nsec = 0;
const volatile unsigned int bucket_range;
const volatile unsigned int min_latency;
const volatile unsigned int max_latency;
SEC("kprobe/func")
int BPF_PROG(func_begin)
{
__u64 key, now;
if (!enabled)
return 0;
key = bpf_get_current_pid_tgid();
if (has_cpu) {
__u32 cpu = bpf_get_smp_processor_id();
__u8 *ok;
ok = bpf_map_lookup_elem(&cpu_filter, &cpu);
if (!ok)
return 0;
}
if (has_task) {
__u32 pid = key & 0xffffffff;
__u8 *ok;
ok = bpf_map_lookup_elem(&task_filter, &pid);
if (!ok)
return 0;
}
now = bpf_ktime_get_ns();
// overwrite timestamp for nested functions
bpf_map_update_elem(&functime, &key, &now, BPF_ANY);
return 0;
}
SEC("kretprobe/func")
int BPF_PROG(func_end)
{
__u64 tid;
__u64 *start;
__u64 cmp_base = use_nsec ? 1 : 1000;
if (!enabled)
return 0;
tid = bpf_get_current_pid_tgid();
start = bpf_map_lookup_elem(&functime, &tid);
if (start) {
__s64 delta = bpf_ktime_get_ns() - *start;
__u32 key = 0;
__u64 *hist;
bpf_map_delete_elem(&functime, &tid);
if (delta < 0)
return 0;
if (bucket_range != 0) {
delta /= cmp_base;
if (min_latency > 0) {
if (delta > min_latency)
delta -= min_latency;
else
goto do_lookup;
}
// Less than 1 unit (ms or ns), or, in the future,
// than the min latency desired.
if (delta > 0) { // 1st entry: [ 1 unit .. bucket_range units )
// clang 12 doesn't like s64 / u32 division
key = (__u64)delta / bucket_range + 1;
if (key >= NUM_BUCKET ||
delta >= max_latency - min_latency)
key = NUM_BUCKET - 1;
}
delta += min_latency;
goto do_lookup;
}
// calculate index using delta
for (key = 0; key < (NUM_BUCKET - 1); key++) {
if (delta < (cmp_base << key))
break;
}
do_lookup:
hist = bpf_map_lookup_elem(&latency, &key);
if (!hist)
return 0;
*hist += 1;
if (bucket_range == 0)
delta /= cmp_base;
__sync_fetch_and_add(&total, delta);
__sync_fetch_and_add(&count, 1);
if (delta > max)
max = delta;
if (delta < min)
min = delta;
}
return 0;
}
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