linux-kernel - Re: [PATCH] perf/x86/intel: Fix debug

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Date:   Mon, 17 Jul 2017 13:37:58 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>
Subject: Re: [PATCH] perf/x86/intel: Fix debug_store reset field for freq
 events

On Fri, Jul 14, 2017 at 10:22:49AM -0700, Andi Kleen wrote:
> Jiri Olsa <jolsa@...nel.org> writes:
> >
> > Setting the reset field to 0 for freq events.
> 
> Looks good to me.
> 
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>
> 
> BTW I suspect there's a related bug that
> 
> perf record -e '{cycles:pp,branches}:S' ..
> 
> would enable multi record PEBS, even though it shouldn't because
> we need the PMI to read the other events.

there's PERF_SAMPLE_READ om cycles's sample_type for this example
so it won't pass the x86_pmu::free_running_flags filter

also PERF_SAMPLE_TIME and PERF_SAMPLE_PERIOD will be set
in your example which will prevent that, but those
could be unset via record's '-c xxxx' and '--no-timestamp'

jirka