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

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Date:   Mon, 17 Jul 2017 11:07:07 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <andi@...stfloor.org>, 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 Mon, Jul 17, 2017 at 01:37:58PM +0200, Jiri Olsa wrote:
> 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

Good thanks for checking.

> 
> 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'

PERF_SAMPLE_TIME works with Skylake/goldmont, but yes forgot 
the -c.

-Andi