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// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
// Copyright (c) 2021 Facebook
// Copyright (c) 2021 Google
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
#define MAX_LEVELS 10 // max cgroup hierarchy level: arbitrary
#define MAX_EVENTS 32 // max events per cgroup: arbitrary
// NOTE: many of map and global data will be modified before loading
// from the userspace (perf tool) using the skeleton helpers.
// single set of global perf events to measure
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(int));
__uint(max_entries, 1);
} events SEC(".maps");
// from cgroup id to event index
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(key_size, sizeof(__u64));
__uint(value_size, sizeof(__u32));
__uint(max_entries, 1);
} cgrp_idx SEC(".maps");
// per-cpu event snapshots to calculate delta
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(struct bpf_perf_event_value));
} prev_readings SEC(".maps");
// aggregated event values for each cgroup (per-cpu)
// will be read from the user-space
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(struct bpf_perf_event_value));
} cgrp_readings SEC(".maps");
const volatile __u32 num_events = 1;
const volatile __u32 num_cpus = 1;
int enabled = 0;
int use_cgroup_v2 = 0;
int perf_subsys_id = -1;
static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
{
struct task_struct *p = (void *)bpf_get_current_task();
struct cgroup *cgrp;
register int i = 0;
__u32 *elem;
int level;
int cnt;
if (perf_subsys_id == -1) {
#if __has_builtin(__builtin_preserve_enum_value)
perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
perf_event_cgrp_id);
#else
perf_subsys_id = perf_event_cgrp_id;
#endif
}
cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_subsys_id], cgroup);
level = BPF_CORE_READ(cgrp, level);
for (cnt = 0; i < MAX_LEVELS; i++) {
__u64 cgrp_id;
if (i > level)
break;
// convert cgroup-id to a map index
cgrp_id = BPF_CORE_READ(cgrp, ancestors[i], kn, id);
elem = bpf_map_lookup_elem(&cgrp_idx, &cgrp_id);
if (!elem)
continue;
cgrps[cnt++] = *elem;
if (cnt == size)
break;
}
return cnt;
}
static inline int get_cgroup_v2_idx(__u32 *cgrps, int size)
{
register int i = 0;
__u32 *elem;
int cnt;
for (cnt = 0; i < MAX_LEVELS; i++) {
__u64 cgrp_id = bpf_get_current_ancestor_cgroup_id(i);
if (cgrp_id == 0)
break;
// convert cgroup-id to a map index
elem = bpf_map_lookup_elem(&cgrp_idx, &cgrp_id);
if (!elem)
continue;
cgrps[cnt++] = *elem;
if (cnt == size)
break;
}
return cnt;
}
static int bperf_cgroup_count(void)
{
register __u32 idx = 0; // to have it in a register to pass BPF verifier
register int c = 0;
struct bpf_perf_event_value val, delta, *prev_val, *cgrp_val;
__u32 cpu = bpf_get_smp_processor_id();
__u32 cgrp_idx[MAX_LEVELS];
int cgrp_cnt;
__u32 key, cgrp;
long err;
if (use_cgroup_v2)
cgrp_cnt = get_cgroup_v2_idx(cgrp_idx, MAX_LEVELS);
else
cgrp_cnt = get_cgroup_v1_idx(cgrp_idx, MAX_LEVELS);
for ( ; idx < MAX_EVENTS; idx++) {
if (idx == num_events)
break;
// XXX: do not pass idx directly (for verifier)
key = idx;
// this is per-cpu array for diff
prev_val = bpf_map_lookup_elem(&prev_readings, &key);
if (!prev_val) {
val.counter = val.enabled = val.running = 0;
bpf_map_update_elem(&prev_readings, &key, &val, BPF_ANY);
prev_val = bpf_map_lookup_elem(&prev_readings, &key);
if (!prev_val)
continue;
}
// read from global perf_event array
key = idx * num_cpus + cpu;
err = bpf_perf_event_read_value(&events, key, &val, sizeof(val));
if (err)
continue;
if (enabled) {
delta.counter = val.counter - prev_val->counter;
delta.enabled = val.enabled - prev_val->enabled;
delta.running = val.running - prev_val->running;
for (c = 0; c < MAX_LEVELS; c++) {
if (c == cgrp_cnt)
break;
cgrp = cgrp_idx[c];
// aggregate the result by cgroup
key = cgrp * num_events + idx;
cgrp_val = bpf_map_lookup_elem(&cgrp_readings, &key);
if (cgrp_val) {
cgrp_val->counter += delta.counter;
cgrp_val->enabled += delta.enabled;
cgrp_val->running += delta.running;
} else {
bpf_map_update_elem(&cgrp_readings, &key,
&delta, BPF_ANY);
}
}
}
*prev_val = val;
}
return 0;
}
// This will be attached to cgroup-switches event for each cpu
SEC("perf_event")
int BPF_PROG(on_cgrp_switch)
{
return bperf_cgroup_count();
}
SEC("raw_tp/sched_switch")
int BPF_PROG(trigger_read)
{
return bperf_cgroup_count();
}
char LICENSE[] SEC("license") = "Dual BSD/GPL";
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