linux-kernel - Re: [PATCH 1/3] perf tools: Fix period/freq terms setup

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Date:   Mon, 5 Feb 2018 12:58:16 -0800
From:   Stephane Eranian <eranian@...gle.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/3] perf tools: Fix period/freq terms setup

On Mon, Feb 5, 2018 at 7:17 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Fri, Feb 02, 2018 at 01:04:34PM -0800, Stephane Eranian wrote:
>> On Fri, Feb 2, 2018 at 12:40 PM, Arnaldo Carvalho de Melo
>> <acme@...nel.org> wrote:
>> > Em Fri, Feb 02, 2018 at 05:28:49PM -0300, Arnaldo Carvalho de Melo escreveu:
>> >> Em Fri, Feb 02, 2018 at 10:45:46AM -0800, Stephane Eranian escreveu:
>> >> > Otherwise, I tested what you have written so far and it works.
>> >
>> >> So I take that as a Tested-by: Stephane and will apply the patches, Jiri
>> >> can continue working on these other aspects, right?
>> >
>> > I also added this for the casual reader to get up to speed more quickly,
>> > please check that it makes sense.
>> >
>> >     Committer note:
>> >
>> >     When we use -c or a period=N term in the event definition, then we don't
>> >     need to ask the kernel, via perf_event_attr.sample_type |=
>> >     PERF_SAMPLE_PERIOD, to put the event period in each sample, as we know
>> >     it already, it is in perf_event_attr.sample_period.
>> >
>> Not quite. It depends on how each event is setup. I can mix & match period
>> and frequency. The PERF_SAMPLE_PERIOD can be dropped only if all the
>> events use a fixed period either via period=N or -c.
>
> I think you can have both period and freq based event in one session
> if that's your concern..? what would be the problem?
>
My understanding was that perf only support configs where all events
have the same attr.sample_type. With frequency mode, you'd want the period
recorded in some cases.

> jirka
>
>> I hope that perf report can deal with config mixing period and fixed
>> mode correctly.