linux-kernel - Re: libperf: lack of interface

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Message-ID: <YTCOVGyffe+VwL6G@krava>
Date:   Thu, 2 Sep 2021 10:41:56 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Nakamura Shun <nakamura.shun@...itsu.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: libperf: lack of interface

On Wed, Sep 01, 2021 at 10:36:40AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Sep 01, 2021 at 09:45:10AM +0000, nakamura.shun@...itsu.com escreveu:
> > Hello.
> > 
> > I'm trying to change rdpmc test in perf_event_tests[1] to use libperf, but libperf doesn't have enough interfaces.
> > Does anyone plan to implement any of these libperf features?
> > 
> > - Interfaces that can run ioctl (PERF_EVENT_IOC_RESET) from userland
> > - Interfaces that can run fcntl (SIGIO) from userland

hi,
we could add perf_evsel__fd like below, would it help your usecase?

if you described your usecases in more details we could
see if we could add/move something to libperf for that

as Arnaldo said below it could be already in tools/perf/util/*.c
somewhere ;-)

jirka


> > 
> > [1] https://github.com/deater/perf_event_tests/tree/master/tests/rdpmc
> 
> So, while in this specific case you should probably follow PeterZ's
> advice, feel free to submit patches moving stuff that is in
> tools/perf/util/ to tools/lib/perf/ (libperf) when you have a reasonable
> use case, such as Vince's test suite.
> 
> We can then discuss if any adjustment is needed, but doing it this
> piecemeal way, with justification, should be a good way to enrich
> libperf with things that are in quiescent state in tools/perf/util/ and
> that have external users.
> 
> Thanks,
> 
> - Arnaldo
> 

---
 tools/lib/perf/evsel.c              | 13 +++++++++++++
 tools/lib/perf/include/perf/evsel.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index d8886720e83d..8cbdaa78749c 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -413,3 +413,16 @@ void perf_evsel__free_id(struct perf_evsel *evsel)
 	zfree(&evsel->id);
 	evsel->ids = 0;
 }
+
+int perf_evsel__fd(struct perf_evsel *evsel, int cpu, int thread)
+{
+	int max_thread = xyarray__max_y(evsel->fd);
+	int max_cpu = xyarray__max_x(evsel->fd);
+
+	if (thread >= max_thread)
+		return -EINVAL;
+	if (cpu >= max_cpu)
+		return -EINVAL;
+
+	return FD(evsel, cpu, thread);
+}
diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
index 60eae25076d3..5f29935efcaf 100644
--- a/tools/lib/perf/include/perf/evsel.h
+++ b/tools/lib/perf/include/perf/evsel.h
@@ -39,5 +39,6 @@ LIBPERF_API int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu);
 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);
+LIBPERF_API int perf_evsel__fd(struct perf_evsel *evsel, int cpu, int thread);
 
 #endif /* __LIBPERF_EVSEL_H */
-- 
2.31.1