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Message-ID: <ZtkyCWXVjnn-hjUT@google.com>
Date: Wed, 4 Sep 2024 21:22:33 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libperf: Add perf_evsel__id() function
Hello,
On Fri, Aug 23, 2024 at 11:58:38AM -0700, Charlie Jenkins wrote:
> Introduce perf_evsel__id() to collect the id of an evsel. It is not
> currently possible when using libperf to determine the id of an evsel.
> This will allow applications to link the id returned by PERF_SAMPLE_ID
> to the event being sampled.
I'm not sure what's your use case. We have evlist__id2evsel() to
convert sample-ID to evsel already. It'd read the IDs from perf data
file.
>
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> tools/lib/perf/Documentation/libperf.txt | 2 ++
> tools/lib/perf/evsel.c | 10 ++++++++++
> tools/lib/perf/include/perf/evsel.h | 1 +
> 3 files changed, 13 insertions(+)
>
> diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
> index fcfb9499ef9c..69c1d7efb659 100644
> --- a/tools/lib/perf/Documentation/libperf.txt
> +++ b/tools/lib/perf/Documentation/libperf.txt
> @@ -94,6 +94,8 @@ SYNOPSIS
> void perf_evlist__enable(struct perf_evlist *evlist);
> void perf_evlist__disable(struct perf_evlist *evlist);
>
> + void perf_evsel__id(struct perf_evsel *evsel, u64 *id);
> +
> #define perf_evlist__for_each_evsel(evlist, pos)
>
> void perf_evlist__set_maps(struct perf_evlist *evlist,
> diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> index c07160953224..765b17045342 100644
> --- a/tools/lib/perf/evsel.c
> +++ b/tools/lib/perf/evsel.c
> @@ -484,6 +484,16 @@ int perf_evsel__disable(struct perf_evsel *evsel)
> return err;
> }
>
> +int perf_evsel__id(struct perf_evsel *evsel, __u64 *id)
> +{
> + int i;
> + int err = 0;
> +
> + for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
> + err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ID, (unsigned long)id, i);
IIUC this would update the place pointed by 'id' for every fd then you
will get the last ID only.
Thanks,
Namhyung
> + return err;
> +}
> +
> int perf_evsel__apply_filter(struct perf_evsel *evsel, const char *filter)
> {
> int err = 0, i;
> diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
> index 6f92204075c2..1457e5a46b28 100644
> --- a/tools/lib/perf/include/perf/evsel.h
> +++ b/tools/lib/perf/include/perf/evsel.h
> @@ -41,6 +41,7 @@ LIBPERF_API int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx
> LIBPERF_API int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread);
> LIBPERF_API int perf_evsel__disable(struct perf_evsel *evsel);
> LIBPERF_API int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
> +LIBPERF_API int perf_evsel__id(struct perf_evsel *evsel, __u64 *id);
> LIBPERF_API struct perf_cpu_map *perf_evsel__cpus(struct perf_evsel *evsel);
> LIBPERF_API struct perf_thread_map *perf_evsel__threads(struct perf_evsel *evsel);
> LIBPERF_API struct perf_event_attr *perf_evsel__attr(struct perf_evsel *evsel);
>
> ---
> base-commit: 47ac09b91befbb6a235ab620c32af719f8208399
> change-id: 20240822-perf_evsel_get_id-f7e11f15504b
> --
> - Charlie
>
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