Re: [RFC 00/73] libperf: Add sampling interface

From: Jiri Olsa <jolsa@redhat.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>,
	Kan Liang <kan.liang@linux.intel.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Ian Rogers <irogers@google.com>,
	Stephane Eranian <eranian@google.com>,
	Song Liu <songliubraving@fb.com>,
	Alexey Budankov <alexey.budankov@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Michael Petlan <mpetlan@redhat.com>
Subject: Re: [RFC 00/73] libperf: Add sampling interface
Date: Sun, 22 Sep 2019 16:47:05 +0200	[thread overview]
Message-ID: <20190922144705.GA17104@krava> (raw)
In-Reply-To: <20190913132355.21634-1-jolsa@kernel.org>

On Fri, Sep 13, 2019 at 03:22:42PM +0200, Jiri Olsa wrote:
> hi,
> sending changes for exporting basic sampling interface
> in libperf. It's now possible to use following code in
> applications via libperf:
> 
> --- (example is without error checks for simplicity)
> 
>   struct perf_event_attr attr = {
>           .type             = PERF_TYPE_TRACEPOINT,
>           .sample_period    = 1,
>           .wakeup_watermark = 1,
>           .disabled         = 1,
>   };
>   /* ... setup attr */
> 
>   cpus = perf_cpu_map__new(NULL);
> 
>   evlist = perf_evlist__new();
>   evsel  = perf_evsel__new(&attr);
>   perf_evlist__add(evlist, evsel);
> 
>   perf_evlist__set_maps(evlist, cpus, NULL);
> 
>   err = perf_evlist__open(evlist);
>   err = perf_evlist__mmap(evlist, 4);
> 
>   err = perf_evlist__enable(evlist);
> 
>   /* ... monitored area, plus all the other cpus */
> 
>   err = perf_evlist__disable(evlist);
> 
>   perf_evlist__for_each_mmap(evlist, map) {
>           if (perf_mmap__read_init(map) < 0)
>                   continue;
> 
>           while ((event = perf_mmap__read_event(map)) != NULL) {
>                   perf_mmap__consume(map);
>           }
> 
>           perf_mmap__read_done(map);
>   }
> 
>   perf_evlist__delete(evlist);
>   perf_cpu_map__put(cpus);
> 
> --- (end)
> 
> Nothing is carved in stone so far, the interface is exported
> as is available in perf now and we can change it as we want.
> 
> New tests are added in test-evlist.c to do thread and cpu based
> sampling.
> 
> All the functionality should not change, however there's considerable
> mmap code rewrite, so would be great if guys could run your usual
> workloads to see if all is fine.. so far so good in my tests ;-)
> 
> It's also available in here:
>   git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
>   perf/lib

hi,
I rebased the branch to latest Arnaldo's perf/core branch

jirka