Hi,
On 2024/10/17 5:16, Namhyung Kim wrote:
> Hello,
>
> On Sat, Oct 12, 2024 at 02:32:24AM +0000, Tengda Wu wrote:
>> bperf has a nice ability to share PMUs, but it still does not support
>> inherit events during fork(), resulting in some deviations in its stat
>> results compared with perf.
>>
>> perf stat result:
>> $ ./perf stat -e cycles,instructions -- ./perf test -w sqrtloop
>>
>> Performance counter stats for './perf test -w sqrtloop':
>>
>> 2,316,038,116 cycles
>> 2,859,350,725 instructions
>>
>> 1.009603637 seconds time elapsed
>>
>> 1.004196000 seconds user
>> 0.003950000 seconds sys
>>
>> bperf stat result:
>> $ ./perf stat --bpf-counters -e cycles,instructions -- \
>> ./perf test -w sqrtloop
>>
>> Performance counter stats for './perf test -w sqrtloop':
>>
>> 18,762,093 cycles
>> 23,487,766 instructions
>>
>> 1.008913769 seconds time elapsed
>>
>> 1.003248000 seconds user
>> 0.004069000 seconds sys
>>
>> In order to support event inheritance, two new bpf programs are added
>> to monitor the fork and exit of tasks respectively. When a task is
>> created, add it to the filter map to enable counting, and reuse the
>> `accum_key` of its parent task to count together with the parent task.
>> When a task exits, remove it from the filter map to disable counting.
>>
>> After support:
>> $ ./perf stat --bpf-counters -e cycles,instructions -- \
>> ./perf test -w sqrtloop
>>
>> Performance counter stats for './perf test -w sqrtloop':
>>
>> 2,316,252,189 cycles
>> 2,859,946,547 instructions
>>
>> 1.009422314 seconds time elapsed
>>
>> 1.003597000 seconds user
>> 0.004270000 seconds sys
>>
>> Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
>> ---
>> tools/perf/builtin-stat.c | 4 +-
>> tools/perf/util/bpf_counter.c | 57 +++++++++---
>> tools/perf/util/bpf_counter.h | 13 ++-
>> tools/perf/util/bpf_counter_cgroup.c | 3 +-
>> tools/perf/util/bpf_skel/bperf_follower.bpf.c | 87 +++++++++++++++++--
>> tools/perf/util/bpf_skel/bperf_u.h | 5 ++
>> 6 files changed, 145 insertions(+), 24 deletions(-)
>>
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index 3e6b9f216e80..c27b107c1985 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -698,6 +698,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>> char msg[BUFSIZ];
>> unsigned long long t0, t1;
>> struct evsel *counter;
>> + struct bpf_stat_opts opts;
>> size_t l;
>> int status = 0;
>> const bool forks = (argc > 0);
>> @@ -725,7 +726,8 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>>
>> evlist__for_each_entry(evsel_list, counter) {
>> counter->reset_group = false;
>> - if (bpf_counter__load(counter, &target)) {
>> + opts.inherit = !stat_config.no_inherit;
>> + if (bpf_counter__load(counter, &target, &opts)) {
>
> Maybe you can just add a boolean member in the struct target.
Yes，this approach would be more straightforward.
I had considered it before, but, as you see, considering that `inherit` does not
align well with the `target` semantics, I chose the another one.
Anyway, I'll try it. Code changes would be more clean. Thanks.
>
>
>> err = -1;
>> goto err_out;
>> }
>> diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
>> index 7a8af60e0f51..00afea6bde63 100644
>> --- a/tools/perf/util/bpf_counter.c
>> +++ b/tools/perf/util/bpf_counter.c
>> @@ -166,7 +166,9 @@ static int bpf_program_profiler_load_one(struct evsel *evsel, u32 prog_id)
>> return -1;
>> }
>>
>> -static int bpf_program_profiler__load(struct evsel *evsel, struct target *target)
>> +static int bpf_program_profiler__load(struct evsel *evsel,
>> + struct target *target,
>> + struct bpf_stat_opts *opts __maybe_unused)
>> {
>> char *bpf_str, *bpf_str_, *tok, *saveptr = NULL, *p;
>> u32 prog_id;
>> @@ -364,6 +366,7 @@ static int bperf_lock_attr_map(struct target *target)
>>
>> static int bperf_check_target(struct evsel *evsel,
>> struct target *target,
>> + struct bpf_stat_opts *opts,
>> enum bperf_filter_type *filter_type,
>> __u32 *filter_entry_cnt)
>> {
>> @@ -383,7 +386,12 @@ static int bperf_check_target(struct evsel *evsel,
>> *filter_type = BPERF_FILTER_PID;
>> *filter_entry_cnt = perf_thread_map__nr(evsel->core.threads);
>> } else if (target->pid || evsel->evlist->workload.pid != -1) {
>> - *filter_type = BPERF_FILTER_TGID;
>> + /*
>> + * unlike the PID type, the TGID type implicitly enables
>> + * event inheritance within a single process.
>> + */
>> + *filter_type = opts->inherit ?
>> + BPERF_FILTER_TGID : BPERF_FILTER_PID;
>
> I'm not sure if it's right. You should be able to use PID type with
> inheritance. In this case child processes or threads from the selected
> thread would be counted only.
Sorry, don't quite understand. TGID type counts together with all sub-threads within
the same process, which is what inheritance needs to do; while PID type only counts
for a single thread and should be used when inheritance is turned off. This is equivalent
to the code above.
Simple test blow:
---
$ ./perf stat -e cpu-clock -- ./perf test -w sqrtloop
Performance counter stats for './perf test -w sqrtloop':
1,022.29 msec cpu-clock # 0.999 CPUs utilized
1.023801331 seconds time elapsed
1.012666000 seconds user
0.010618000 seconds sys
$ ./perf stat -e cpu-clock -i -- ./perf test -w sqrtloop
Performance counter stats for './perf test -w sqrtloop':
19.85 msec cpu-clock # 0.019 CPUs utilized
1.023108515 seconds time elapsed
1.008862000 seconds user
0.014346000 seconds sys
$ ./perf stat --bpf-counters -e cpu-clock -- ./perf test -w sqrtloop
Performance counter stats for './perf test -w sqrtloop':
1,022.77 msec cpu-clock # 0.986 CPUs utilized
1.037375618 seconds time elapsed
1.014952000 seconds user
0.008047000 seconds sys
$ ./perf stat --bpf-counters -e cpu-clock -i -- ./perf test -w sqrtloop
Performance counter stats for './perf test -w sqrtloop':
18.88 msec cpu-clock # 0.018 CPUs utilized
1.021336780 seconds time elapsed
0.998283000 seconds user
0.023079000 seconds sys
As we can see, the perf and bperf counts are consistent before and after enabling
-i(--no-inherit), which means the TGID and PID type switch works well.
Thanks,
Tengda
>
> Thanks,
> Namhyung
>
>
>> *filter_entry_cnt = perf_thread_map__nr(evsel->core.threads);
>> } else {
>> pr_err("bpf managed perf events do not yet support these targets.\n");
>> @@ -394,6 +402,7 @@ static int bperf_check_target(struct evsel *evsel,
>> }
>>
>> static struct perf_cpu_map *all_cpu_map;
>> +static __u32 filter_entry_cnt;
>>
>> static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
>> struct perf_event_attr_map_entry *entry)
>> @@ -444,14 +453,36 @@ static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
>> return err;
>> }
>>
>> -static int bperf__load(struct evsel *evsel, struct target *target)
>> +static int bperf_attach_follower_program(struct bperf_follower_bpf *skel,
>> + enum bperf_filter_type filter_type,
>> + bool inherit)
>> +{
>> + struct bpf_link *link;
>> + int err = 0;
>> +
>> + if ((filter_type == BPERF_FILTER_PID ||
>> + filter_type == BPERF_FILTER_TGID) && inherit)
>> + /* attach all follower bpf progs to enable event inheritance */
>> + err = bperf_follower_bpf__attach(skel);
>> + else {
>> + link = bpf_program__attach(skel->progs.fexit_XXX);
>> + if (IS_ERR(link))
>> + err = PTR_ERR(link);
>> + }
>> +
>> + return err;
>> +}
>> +
>> +static int bperf__load(struct evsel *evsel, struct target *target,
>> + struct bpf_stat_opts *opts)
>> {
>> struct perf_event_attr_map_entry entry = {0xffffffff, 0xffffffff};
>> int attr_map_fd, diff_map_fd = -1, err;
>> enum bperf_filter_type filter_type;
>> - __u32 filter_entry_cnt, i;
>> + __u32 i;
>>
>> - if (bperf_check_target(evsel, target, &filter_type, &filter_entry_cnt))
>> + if (bperf_check_target(evsel, target, opts, &filter_type,
>> + &filter_entry_cnt))
>> return -1;
>>
>> if (!all_cpu_map) {
>> @@ -529,9 +560,6 @@ static int bperf__load(struct evsel *evsel, struct target *target)
>> /* set up reading map */
>> bpf_map__set_max_entries(evsel->follower_skel->maps.accum_readings,
>> filter_entry_cnt);
>> - /* set up follower filter based on target */
>> - bpf_map__set_max_entries(evsel->follower_skel->maps.filter,
>> - filter_entry_cnt);
>> err = bperf_follower_bpf__load(evsel->follower_skel);
>> if (err) {
>> pr_err("Failed to load follower skeleton\n");
>> @@ -543,6 +571,7 @@ static int bperf__load(struct evsel *evsel, struct target *target)
>> for (i = 0; i < filter_entry_cnt; i++) {
>> int filter_map_fd;
>> __u32 key;
>> + struct bperf_filter_value fval = { i, 0 };
>>
>> if (filter_type == BPERF_FILTER_PID ||
>> filter_type == BPERF_FILTER_TGID)
>> @@ -553,12 +582,13 @@ static int bperf__load(struct evsel *evsel, struct target *target)
>> break;
>>
>> filter_map_fd = bpf_map__fd(evsel->follower_skel->maps.filter);
>> - bpf_map_update_elem(filter_map_fd, &key, &i, BPF_ANY);
>> + bpf_map_update_elem(filter_map_fd, &key, &fval, BPF_ANY);
>> }
>>
>> evsel->follower_skel->bss->type = filter_type;
>>
>> - err = bperf_follower_bpf__attach(evsel->follower_skel);
>> + err = bperf_attach_follower_program(evsel->follower_skel, filter_type,
>> + opts->inherit);
>>
>> out:
>> if (err && evsel->bperf_leader_link_fd >= 0)
>> @@ -623,7 +653,7 @@ static int bperf__read(struct evsel *evsel)
>> bperf_sync_counters(evsel);
>> reading_map_fd = bpf_map__fd(skel->maps.accum_readings);
>>
>> - for (i = 0; i < bpf_map__max_entries(skel->maps.accum_readings); i++) {
>> + for (i = 0; i < filter_entry_cnt; i++) {
>> struct perf_cpu entry;
>> __u32 cpu;
>>
>> @@ -776,7 +806,8 @@ int bpf_counter__install_pe(struct evsel *evsel, int cpu_map_idx, int fd)
>> return evsel->bpf_counter_ops->install_pe(evsel, cpu_map_idx, fd);
>> }
>>
>> -int bpf_counter__load(struct evsel *evsel, struct target *target)
>> +int bpf_counter__load(struct evsel *evsel, struct target *target,
>> + struct bpf_stat_opts *opts)
>> {
>> if (target->bpf_str)
>> evsel->bpf_counter_ops = &bpf_program_profiler_ops;
>> @@ -787,7 +818,7 @@ int bpf_counter__load(struct evsel *evsel, struct target *target)
>> evsel->bpf_counter_ops = &bperf_ops;
>>
>> if (evsel->bpf_counter_ops)
>> - return evsel->bpf_counter_ops->load(evsel, target);
>> + return evsel->bpf_counter_ops->load(evsel, target, opts);
>> return 0;
>> }
>>
>> diff --git a/tools/perf/util/bpf_counter.h b/tools/perf/util/bpf_counter.h
>> index c6d21c07b14c..70d7869c0cd6 100644
>> --- a/tools/perf/util/bpf_counter.h
>> +++ b/tools/perf/util/bpf_counter.h
>> @@ -15,9 +15,14 @@ struct evsel;
>> struct target;
>> struct bpf_counter;
>>
>> +struct bpf_stat_opts {
>> + bool inherit;
>> +};
>> +
>> typedef int (*bpf_counter_evsel_op)(struct evsel *evsel);
>> typedef int (*bpf_counter_evsel_target_op)(struct evsel *evsel,
>> - struct target *target);
>> + struct target *target,
>> + struct bpf_stat_opts *opts);
>> typedef int (*bpf_counter_evsel_install_pe_op)(struct evsel *evsel,
>> int cpu_map_idx,
>> int fd);
>> @@ -38,7 +43,8 @@ struct bpf_counter {
>>
>> #ifdef HAVE_BPF_SKEL
>>
>> -int bpf_counter__load(struct evsel *evsel, struct target *target);
>> +int bpf_counter__load(struct evsel *evsel, struct target *target,
>> + struct bpf_stat_opts *opts);
>> int bpf_counter__enable(struct evsel *evsel);
>> int bpf_counter__disable(struct evsel *evsel);
>> int bpf_counter__read(struct evsel *evsel);
>> @@ -50,7 +56,8 @@ int bpf_counter__install_pe(struct evsel *evsel, int cpu_map_idx, int fd);
>> #include <linux/err.h>
>>
>> static inline int bpf_counter__load(struct evsel *evsel __maybe_unused,
>> - struct target *target __maybe_unused)
>> + struct target *target __maybe_unused,
>> + struct bpf_stat_opts *opts __maybe_unused)
>> {
>> return 0;
>> }
>> diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c
>> index 6ff42619de12..755f12a6703c 100644
>> --- a/tools/perf/util/bpf_counter_cgroup.c
>> +++ b/tools/perf/util/bpf_counter_cgroup.c
>> @@ -167,7 +167,8 @@ static int bperf_load_program(struct evlist *evlist)
>> }
>>
>> static int bperf_cgrp__load(struct evsel *evsel,
>> - struct target *target __maybe_unused)
>> + struct target *target __maybe_unused,
>> + struct bpf_stat_opts *opts __maybe_unused)
>> {
>> static bool bperf_loaded = false;
>>
>> diff --git a/tools/perf/util/bpf_skel/bperf_follower.bpf.c b/tools/perf/util/bpf_skel/bperf_follower.bpf.c
>> index f193998530d4..e804b2a9d0a6 100644
>> --- a/tools/perf/util/bpf_skel/bperf_follower.bpf.c
>> +++ b/tools/perf/util/bpf_skel/bperf_follower.bpf.c
>> @@ -5,6 +5,8 @@
>> #include <bpf/bpf_tracing.h>
>> #include "bperf_u.h"
>>
>> +#define MAX_ENTRIES 102400
>> +
>> struct {
>> __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
>> __uint(key_size, sizeof(__u32));
>> @@ -22,7 +24,9 @@ struct {
>> struct {
>> __uint(type, BPF_MAP_TYPE_HASH);
>> __uint(key_size, sizeof(__u32));
>> - __uint(value_size, sizeof(__u32));
>> + __uint(value_size, sizeof(struct bperf_filter_value));
>> + __uint(max_entries, MAX_ENTRIES);
>> + __uint(map_flags, BPF_F_NO_PREALLOC);
>> } filter SEC(".maps");
>>
>> enum bperf_filter_type type = 0;
>> @@ -33,14 +37,15 @@ int BPF_PROG(fexit_XXX)
>> {
>> struct bpf_perf_event_value *diff_val, *accum_val;
>> __u32 filter_key, zero = 0;
>> - __u32 *accum_key;
>> + __u32 accum_key;
>> + struct bperf_filter_value *fval;
>>
>> if (!enabled)
>> return 0;
>>
>> switch (type) {
>> case BPERF_FILTER_GLOBAL:
>> - accum_key = &zero;
>> + accum_key = zero;
>> goto do_add;
>> case BPERF_FILTER_CPU:
>> filter_key = bpf_get_smp_processor_id();
>> @@ -55,16 +60,20 @@ int BPF_PROG(fexit_XXX)
>> return 0;
>> }
>>
>> - accum_key = bpf_map_lookup_elem(&filter, &filter_key);
>> - if (!accum_key)
>> + fval = bpf_map_lookup_elem(&filter, &filter_key);
>> + if (!fval)
>> return 0;
>>
>> + accum_key = fval->accum_key;
>> + if (fval->exited)
>> + bpf_map_delete_elem(&filter, &filter_key);
>> +
>> do_add:
>> diff_val = bpf_map_lookup_elem(&diff_readings, &zero);
>> if (!diff_val)
>> return 0;
>>
>> - accum_val = bpf_map_lookup_elem(&accum_readings, accum_key);
>> + accum_val = bpf_map_lookup_elem(&accum_readings, &accum_key);
>> if (!accum_val)
>> return 0;
>>
>> @@ -75,4 +84,70 @@ int BPF_PROG(fexit_XXX)
>> return 0;
>> }
>>
>> +/* The program is only used for PID or TGID filter types. */
>> +SEC("tp_btf/task_newtask")
>> +int BPF_PROG(on_newtask, struct task_struct *task, __u64 clone_flags)
>> +{
>> + __u32 parent_key, child_key;
>> + struct bperf_filter_value *parent_fval;
>> + struct bperf_filter_value child_fval = { 0 };
>> +
>> + if (!enabled)
>> + return 0;
>> +
>> + switch (type) {
>> + case BPERF_FILTER_PID:
>> + parent_key = bpf_get_current_pid_tgid() & 0xffffffff;
>> + child_key = task->pid;
>> + break;
>> + case BPERF_FILTER_TGID:
>> + parent_key = bpf_get_current_pid_tgid() >> 32;
>> + child_key = task->tgid;
>> + if (child_key == parent_key)
>> + return 0;
>> + break;
>> + default:
>> + return 0;
>> + }
>> +
>> + /* Check if the current task is one of the target tasks to be counted */
>> + parent_fval = bpf_map_lookup_elem(&filter, &parent_key);
>> + if (!parent_fval)
>> + return 0;
>> +
>> + /* Start counting for the new task by adding it into filter map,
>> + * inherit the accum key of its parent task so that they can be
>> + * counted together.
>> + */
>> + child_fval.accum_key = parent_fval->accum_key;
>> + child_fval.exited = 0;
>> + bpf_map_update_elem(&filter, &child_key, &child_fval, BPF_NOEXIST);
>> +
>> + return 0;
>> +}
>> +
>> +/* The program is only used for PID or TGID filter types. */
>> +SEC("tp_btf/sched_process_exit")
>> +int BPF_PROG(on_exittask, struct task_struct *task)
>> +{
>> + __u32 pid;
>> + struct bperf_filter_value *fval;
>> +
>> + if (!enabled)
>> + return 0;
>> +
>> + /* Stop counting for this task by removing it from filter map.
>> + * For TGID type, if the pid can be found in the map, it means that
>> + * this pid belongs to the leader task. After the task exits, the
>> + * tgid of its child tasks (if any) will be 1, so the pid can be
>> + * safely removed.
>> + */
>> + pid = task->pid;
>> + fval = bpf_map_lookup_elem(&filter, &pid);
>> + if (fval)
>> + fval->exited = 1;
>> +
>> + return 0;
>> +}
>> +
>> char LICENSE[] SEC("license") = "Dual BSD/GPL";
>> diff --git a/tools/perf/util/bpf_skel/bperf_u.h b/tools/perf/util/bpf_skel/bperf_u.h
>> index 1ce0c2c905c1..4a4a753980be 100644
>> --- a/tools/perf/util/bpf_skel/bperf_u.h
>> +++ b/tools/perf/util/bpf_skel/bperf_u.h
>> @@ -11,4 +11,9 @@ enum bperf_filter_type {
>> BPERF_FILTER_TGID,
>> };
>>
>> +struct bperf_filter_value {
>> + __u32 accum_key;
>> + __u8 exited;
>> +};
>> +
>> #endif /* __BPERF_STAT_U_H */
>> --
>> 2.34.1
>>
