| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <aDojkKOJCgvlgL2x@google.com>
Date: Fri, 30 May 2025 14:30:56 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Howard Chu <howardchu95@...il.com>
Cc: acme@...nel.org, mingo@...hat.com, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com, peterz@...radead.org,
kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] perf trace: Enhance task filtering
Hi Howard,
On Thu, May 29, 2025 at 11:24:07PM -0700, Howard Chu wrote:
> This patch does two things:
> 1. Add a pids_targeted map, put pids that interest perf trace in.
> 2. Make bpf-output event system-wide.
>
> Effect 1:
> perf trace doesn't augment threads properly. With the script below:
>
> Program test_trace_loop.c
> ~~~
> #include <pthread.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <stdlib.h>
>
> #define THREAD_NR 2
>
> struct thread_arg {
> int index;
> };
>
> void *func(void *arg) {
> struct thread_arg *t_arg = arg;
> while (1) {
> printf("thread %d running\n", t_arg->index);
> sleep(1);
> }
> return NULL;
> }
>
> int main()
> {
> pthread_t thread_ids[THREAD_NR];
> struct thread_arg thread_args[THREAD_NR];
>
> for (int i = 0; i < THREAD_NR; i++) {
> thread_args[i].index = i;
> if (pthread_create(&thread_ids[i], NULL, &func, &thread_args[i])) {
> perror("failed to create thread, exiting\n");
> exit(1);
> }
> }
>
> while (1) {
> printf("parent sleeping\n");
> sleep(1);
> }
>
> for (int i = 0; i < THREAD_NR; i++)
> pthread_join(thread_ids[i], NULL);
>
> return 0;
> }
> ~~~
>
> Commands
> ~~~
> $ gcc test_trace_loop.c -o test_trace_loop
>
> $ ./test_trace_loop &
> [1] 1404183
>
> $ pstree 1404183 -p
> test_trace_loop(1404183)─┬─{test_trace_loop}(1404185)
> └─{test_trace_loop}(1404186)
>
> $ sudo perf trace -p 1404183 -e *sleep
> ~~~
>
> Output
> before:
> $ sudo /tmp/perf/perf trace -p 1404183 -e *sleep
> ? ( ): test_trace_loo/1404186 ... [continued]: clock_nanosleep()) = 0
> ? ( ): test_trace_loo/1404183 ... [continued]: clock_nanosleep()) = 0
> 0.119 ( ): test_trace_loo/1404186 clock_nanosleep(rqtp: 0x7a86061fde60, rmtp: 0x7a86061fde60) ...
> ? ( ): test_trace_loo/1404185 ... [continued]: clock_nanosleep()) = 0
> 0.047 ( ): test_trace_loo/1404183 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7ffd89091450) ...
> 0.047 (1000.127 ms): test_trace_loo/1404183 ... [continued]: clock_nanosleep()) = 0
>
> explanation: only the parent thread 1404183 got augmented
>
> after:
> $ sudo /tmp/perf/perf trace -p 1404183 -e *sleep
> ? ( ): test_trace_loo/1404183 ... [continued]: clock_nanosleep()) = 0
> ? ( ): test_trace_loo/1404186 ... [continued]: clock_nanosleep()) = 0
> 0.147 ( ): test_trace_loo/1404186 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7a86061fde60) ...
> ? ( ): test_trace_loo/1404185 ... [continued]: clock_nanosleep()) = 0
> 0.076 ( ): test_trace_loo/1404183 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7ffd89091450) ...
> 0.076 (1000.160 ms): test_trace_loo/1404183 ... [continued]: clock_nanosleep()) = 0
> 0.147 (1000.090 ms): test_trace_loo/1404186 ... [continued]: clock_nanosleep()) = 0
> 2.557 ( ): test_trace_loo/1404185 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7a86069fee60) ...
> 1000.323 ( ): test_trace_loo/1404186 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7a86061fde60) ...
> 2.557 (1000.129 ms): test_trace_loo/1404185 ... [continued]: clock_nanosleep()) = 0
> 1000.384 ( ): test_trace_loo/1404183 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7ffd89091450) ...
>
> explanation: all threads augmented
>
> Effect 2: perf trace doesn't collect syscall argument data for *ALL*
> pids, and throw it away anymore. Those uninteresting pids get filtered
> right away. There should be a performance advantage.
Thanks for doing this!
>
> Signed-off-by: Howard Chu <howardchu95@...il.com>
> ---
> tools/perf/builtin-trace.c | 52 ++++++++++++++++---
> .../bpf_skel/augmented_raw_syscalls.bpf.c | 35 ++++++++++---
> tools/perf/util/evlist.c | 2 +-
> 3 files changed, 73 insertions(+), 16 deletions(-)
>
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index 67b557ec3b0d..11620cb40198 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -4377,6 +4377,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> unsigned long before;
> const bool forks = argc > 0;
> bool draining = false;
> + bool enable_evlist = false;
>
> trace->live = true;
>
> @@ -4447,6 +4448,9 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> evlist__set_default_cgroup(trace->evlist, trace->cgroup);
>
> create_maps:
> + if (trace->syscalls.events.bpf_output)
> + trace->syscalls.events.bpf_output->core.system_wide = true;
> +
> err = evlist__create_maps(evlist, &trace->opts.target);
> if (err < 0) {
> fprintf(trace->output, "Problems parsing the target to trace, check your options!\n");
> @@ -4481,20 +4485,54 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> goto out_error_open;
> #ifdef HAVE_BPF_SKEL
> if (trace->syscalls.events.bpf_output) {
> + struct perf_evsel *perf_evsel = &trace->syscalls.events.bpf_output->core;
> struct perf_cpu cpu;
> + bool t = true;
> +
> + enable_evlist = true;
> + if (trace->opts.target.system_wide)
> + trace->skel->bss->system_wide = true;
> + else
> + trace->skel->bss->system_wide = false;
>
> /*
> * Set up the __augmented_syscalls__ BPF map to hold for each
> * CPU the bpf-output event's file descriptor.
> */
> - perf_cpu_map__for_each_cpu(cpu, i, trace->syscalls.events.bpf_output->core.cpus) {
> + perf_cpu_map__for_each_cpu(cpu, i, perf_evsel->cpus) {
> int mycpu = cpu.cpu;
>
> - bpf_map__update_elem(trace->skel->maps.__augmented_syscalls__,
> - &mycpu, sizeof(mycpu),
> - xyarray__entry(trace->syscalls.events.bpf_output->core.fd,
> - mycpu, 0),
> - sizeof(__u32), BPF_ANY);
> + err = bpf_map__update_elem(trace->skel->maps.__augmented_syscalls__,
> + &mycpu, sizeof(mycpu),
> + xyarray__entry(perf_evsel->fd, mycpu, 0),
> + sizeof(__u32), BPF_ANY);
> + if (err) {
> + pr_err("Couldn't set system-wide bpf output perf event fd"
> + ", err: %d\n", err);
> + goto out_disable;
> + }
> + }
> +
> + if (target__has_task(&trace->opts.target)) {
> + struct perf_thread_map *threads = trace->evlist->core.threads;
> +
> + for (int thread = 0; thread < perf_thread_map__nr(threads); thread++) {
> + pid_t pid = perf_thread_map__pid(threads, thread);
> +
> + err = bpf_map__update_elem(trace->skel->maps.pids_targeted, &pid,
> + sizeof(pid), &t, sizeof(t), BPF_ANY);
> + if (err) {
> + pr_err("Couldn't set pids_targeted map, err: %d\n", err);
> + goto out_disable;
> + }
> + }
> + } else if (workload_pid != -1) {
> + err = bpf_map__update_elem(trace->skel->maps.pids_targeted, &workload_pid,
> + sizeof(workload_pid), &t, sizeof(t), BPF_ANY);
> + if (err) {
> + pr_err("Couldn't set pids_targeted map for workload, err: %d\n", err);
> + goto out_disable;
> + }
> }
> }
>
> @@ -4553,7 +4591,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
> goto out_error_mmap;
> }
>
> - if (!target__none(&trace->opts.target) && !trace->opts.target.initial_delay)
> + if (enable_evlist || (!target__none(&trace->opts.target) && !trace->opts.target.initial_delay))
I guess target__none() should not call evlist__enable() here.
> evlist__enable(evlist);
>
> if (forks)
> diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> index e4352881e3fa..e517eec7290b 100644
> --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> @@ -26,6 +26,7 @@
> #define is_power_of_2(n) (n != 0 && ((n & (n - 1)) == 0))
>
> #define MAX_CPUS 4096
> +#define MAX_PIDS 4096
>
> /* bpf-output associated map */
> struct __augmented_syscalls__ {
> @@ -113,6 +114,15 @@ struct pids_filtered {
> __uint(max_entries, 64);
> } pids_filtered SEC(".maps");
>
> +volatile bool system_wide;
> +
> +struct pids_targeted {
> + __uint(type, BPF_MAP_TYPE_HASH);
> + __type(key, pid_t);
> + __type(value, bool);
> + __uint(max_entries, MAX_PIDS);
> +} pids_targeted SEC(".maps");
> +
> struct augmented_args_payload {
> struct syscall_enter_args args;
> struct augmented_arg arg, arg2; // We have to reserve space for two arguments (rename, etc)
> @@ -145,6 +155,11 @@ struct beauty_payload_enter_map {
> __uint(max_entries, 1);
> } beauty_payload_enter_map SEC(".maps");
>
> +static pid_t getpid(void)
> +{
> + return bpf_get_current_pid_tgid();
> +}
> +
> static inline struct augmented_args_payload *augmented_args_payload(void)
> {
> int key = 0;
> @@ -418,14 +433,18 @@ int sys_enter_nanosleep(struct syscall_enter_args *args)
> return 1; /* Failure: don't filter */
> }
>
> -static pid_t getpid(void)
> +static bool filter_pid(void)
> {
> - return bpf_get_current_pid_tgid();
> -}
> + if (system_wide)
> + return false;
Doesn't it need to check CPU list when -C option is used?
>
> -static bool pid_filter__has(struct pids_filtered *pids, pid_t pid)
> -{
> - return bpf_map_lookup_elem(pids, &pid) != NULL;
> + pid_t pid = getpid();
> +
> + if (bpf_map_lookup_elem(&pids_targeted, &pid) &&
> + !bpf_map_lookup_elem(&pids_filtered, &pid))
Can we just use a single map for this purpose?
Thanks,
Namhyung
> + return false;
> +
> + return true;
> }
>
> static int augment_sys_enter(void *ctx, struct syscall_enter_args *args)
> @@ -534,7 +553,7 @@ int sys_enter(struct syscall_enter_args *args)
> * initial, non-augmented raw_syscalls:sys_enter payload.
> */
>
> - if (pid_filter__has(&pids_filtered, getpid()))
> + if (filter_pid())
> return 0;
>
> augmented_args = augmented_args_payload();
> @@ -560,7 +579,7 @@ int sys_exit(struct syscall_exit_args *args)
> {
> struct syscall_exit_args exit_args;
>
> - if (pid_filter__has(&pids_filtered, getpid()))
> + if (filter_pid())
> return 0;
>
> bpf_probe_read_kernel(&exit_args, sizeof(exit_args), args);
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index dcd1130502df..7b5837c6e6bb 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1012,7 +1012,7 @@ int evlist__create_maps(struct evlist *evlist, struct target *target)
> if (!threads)
> return -1;
>
> - if (target__uses_dummy_map(target) && !evlist__has_bpf_output(evlist))
> + if (target__uses_dummy_map(target))
> cpus = perf_cpu_map__new_any_cpu();
> else
> cpus = perf_cpu_map__new(target->cpu_list);
> --
> 2.45.2
>
Powered by blists - more mailing lists