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Message-ID: <f587fc70-deca-4db5-a3c5-c8ace9e83493@linaro.org>
Date: Mon, 6 Jan 2025 17:14:15 +0000
From: James Clark <james.clark@...aro.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...nel.org>, Ian Rogers <irogers@...gle.com>,
Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [PATCH 1/3] perf ftrace: Add --stats option to latency subcommand
On 03/01/2025 11:16 pm, Namhyung Kim wrote:
> Sometimes users also want to see average latency as well as histogram.
> The --stats option is to display latency statistics at the end.
>
> $ sudo ./perf ftrace latency -ab --stats -T synchronize_rcu -- ...
> # DURATION | COUNT | GRAPH |
> 0 - 1 us | 0 | |
> 1 - 2 us | 0 | |
> 2 - 4 us | 0 | |
> 4 - 8 us | 0 | |
> 8 - 16 us | 0 | |
> 16 - 32 us | 0 | |
> 32 - 64 us | 0 | |
> 64 - 128 us | 0 | |
> 128 - 256 us | 0 | |
> 256 - 512 us | 0 | |
> 512 - 1024 us | 0 | |
> 1 - 2 ms | 0 | |
> 2 - 4 ms | 0 | |
> 4 - 8 ms | 0 | |
> 8 - 16 ms | 1 | ##### |
> 16 - 32 ms | 7 | ######################################## |
> 32 - 64 ms | 0 | |
> 64 - 128 ms | 0 | |
> 128 - 256 ms | 0 | |
> 256 - 512 ms | 0 | |
> 512 - 1024 ms | 0 | |
> 1 - ... s | 0 | |
>
> # statistics (in usec)
> total time: 171832
> avg time: 21479
> max time: 30906
> min time: 15869
> count: 8
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
> tools/perf/Documentation/perf-ftrace.txt | 4 ++++
> tools/perf/builtin-ftrace.c | 24 ++++++++++++++++++++-
> tools/perf/util/bpf_ftrace.c | 16 ++++++++++++--
> tools/perf/util/bpf_skel/func_latency.bpf.c | 19 ++++++++++++++++
> tools/perf/util/ftrace.h | 4 +++-
> 5 files changed, 63 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
> index eccc0483f7faecad..16b067eb5d84746d 100644
> --- a/tools/perf/Documentation/perf-ftrace.txt
> +++ b/tools/perf/Documentation/perf-ftrace.txt
> @@ -160,6 +160,10 @@ OPTIONS for 'perf ftrace latency'
> -n/--use-nsec). The setting is ignored if the value results in more than
> 22 buckets.
>
> +--stats::
> + Display latency statistics at the end.
> +
> +
> OPTIONS for 'perf ftrace profile'
> ---------------------------------
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 834074162a63bf2b..0ac2b20b272bd790 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -43,6 +43,8 @@
> static volatile sig_atomic_t workload_exec_errno;
> static volatile sig_atomic_t done;
>
> +static struct stats latency_stats; /* for tracepoints */
> +
> static void sig_handler(int sig __maybe_unused)
> {
> done = true;
> @@ -801,6 +803,13 @@ static void make_histogram(struct perf_ftrace *ftrace, int buckets[],
> do_inc:
> buckets[i]++;
>
> + if (ftrace->stats) {
> + if (num >= min_latency)
> + num += min_latency;
> +
> + update_stats(&latency_stats, num);
> + }
> +
> next:
> /* empty the line buffer for the next output */
> linebuf[0] = '\0';
> @@ -894,6 +903,14 @@ static void display_histogram(struct perf_ftrace *ftrace, int buckets[])
> printf(" | %10d | %.*s%*s |\n", buckets[NUM_BUCKET - 1],
> bar_len, bar, bar_total - bar_len, "");
>
> + if (ftrace->stats) {
> + printf("\n# statistics (in %s)\n", ftrace->use_nsec ? "nsec" : "usec");
> + printf(" total time: %20.0f\n", latency_stats.mean * latency_stats.n);
> + printf(" avg time: %20.0f\n", latency_stats.mean);
> + printf(" max time: %20"PRIu64"\n", latency_stats.max);
> + printf(" min time: %20"PRIu64"\n", latency_stats.min);
> + printf(" count: %20.0f\n", latency_stats.n);
> + }
> }
>
> static int prepare_func_latency(struct perf_ftrace *ftrace)
> @@ -932,6 +949,9 @@ static int prepare_func_latency(struct perf_ftrace *ftrace)
> if (fd < 0)
> pr_err("failed to open trace_pipe\n");
>
> + if (ftrace->stats)
> + init_stats(&latency_stats);
> +
> put_tracing_file(trace_file);
> return fd;
> }
> @@ -961,7 +981,7 @@ static int stop_func_latency(struct perf_ftrace *ftrace)
> static int read_func_latency(struct perf_ftrace *ftrace, int buckets[])
> {
> if (ftrace->target.use_bpf)
> - return perf_ftrace__latency_read_bpf(ftrace, buckets);
> + return perf_ftrace__latency_read_bpf(ftrace, buckets, &latency_stats);
>
> return 0;
> }
> @@ -1620,6 +1640,8 @@ int cmd_ftrace(int argc, const char **argv)
> "Minimum latency (1st bucket). Works only with --bucket-range."),
> OPT_UINTEGER(0, "max-latency", &ftrace.max_latency,
> "Maximum latency (last bucket). Works only with --bucket-range and total buckets less than 22."),
> + OPT_BOOLEAN(0, "stats", &ftrace.stats,
> + "Collect function latency stats too"),
> OPT_PARENT(common_options),
> };
> const struct option profile_options[] = {
> diff --git a/tools/perf/util/bpf_ftrace.c b/tools/perf/util/bpf_ftrace.c
> index bc484e65fb8f69ca..ecd5e16df9730e0d 100644
> --- a/tools/perf/util/bpf_ftrace.c
> +++ b/tools/perf/util/bpf_ftrace.c
> @@ -11,6 +11,7 @@
> #include "util/debug.h"
> #include "util/evlist.h"
> #include "util/bpf_counter.h"
> +#include "util/stat.h"
>
> #include "util/bpf_skel/func_latency.skel.h"
>
> @@ -53,6 +54,7 @@ int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace)
> }
>
> skel->rodata->use_nsec = ftrace->use_nsec;
> + skel->rodata->stats = ftrace->stats;
>
> set_max_rlimit();
>
> @@ -86,6 +88,9 @@ int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace)
> }
> }
>
> + if (ftrace->stats)
> + skel->bss->min = INT64_MAX;
> +
> skel->links.func_begin = bpf_program__attach_kprobe(skel->progs.func_begin,
> false, func->name);
> if (IS_ERR(skel->links.func_begin)) {
> @@ -121,8 +126,8 @@ int perf_ftrace__latency_stop_bpf(struct perf_ftrace *ftrace __maybe_unused)
> return 0;
> }
>
> -int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace __maybe_unused,
> - int buckets[])
> +int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace,
> + int buckets[], struct stats *stats)
> {
> int i, fd, err;
> u32 idx;
> @@ -146,6 +151,13 @@ int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace __maybe_unused,
> buckets[idx] += hist[i];
> }
>
> + if (ftrace->stats && skel->bss->count) {
> + stats->mean = skel->bss->total / skel->bss->count;
> + stats->n = skel->bss->count;
> + stats->max = skel->bss->max;
> + stats->min = skel->bss->min;
> + }
> +
> free(hist);
> return 0;
> }
> diff --git a/tools/perf/util/bpf_skel/func_latency.bpf.c b/tools/perf/util/bpf_skel/func_latency.bpf.c
> index 4df54e1b1411b10a..9b68eea8fd444699 100644
> --- a/tools/perf/util/bpf_skel/func_latency.bpf.c
> +++ b/tools/perf/util/bpf_skel/func_latency.bpf.c
> @@ -38,12 +38,19 @@ struct {
>
> 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;
> +const volatile int stats = 0;
>
> SEC("kprobe/func")
> int BPF_PROG(func_begin)
> @@ -136,6 +143,18 @@ int BPF_PROG(func_end)
> return 0;
>
> *hist += 1;
> +
> + if (stats) {
> + 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;
> diff --git a/tools/perf/util/ftrace.h b/tools/perf/util/ftrace.h
> index f218703063f74786..76038ed712085fbc 100644
> --- a/tools/perf/util/ftrace.h
> +++ b/tools/perf/util/ftrace.h
> @@ -7,6 +7,7 @@
>
> struct evlist;
> struct hashamp;
> +struct stats;
>
> struct perf_ftrace {
> struct evlist *evlist;
> @@ -23,6 +24,7 @@ struct perf_ftrace {
> unsigned int bucket_range;
> unsigned int min_latency;
> unsigned int max_latency;
> + bool stats;
> int graph_depth;
> int func_stack_trace;
> int func_irq_info;
> @@ -46,7 +48,7 @@ int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace);
> int perf_ftrace__latency_start_bpf(struct perf_ftrace *ftrace);
> int perf_ftrace__latency_stop_bpf(struct perf_ftrace *ftrace);
> int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace,
> - int buckets[]);
> + int buckets[], struct stats *stats);
Hi Namhyung,
There's a stub below for !HAVE_BPF_SKEL that needs updating too.
Also a minor point, but it seems quite low impact so it could be always
on and then get rid of the --stats option.
Other than that:
Reviewed-by: James Clark <james.clark@...aro.org>
> int perf_ftrace__latency_cleanup_bpf(struct perf_ftrace *ftrace);
>
> #else /* !HAVE_BPF_SKEL */
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