linux-kernel - Re: [RFC 3/6] perf/core: use rb-tree to sched in event groups

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Date:   Thu, 12 Jan 2017 10:11:37 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     "Liang, Kan" <kan.liang@...el.com>
Cc:     David Carrillo-Cisneros <davidcc@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andi Kleen <ak@...ux.intel.com>, Borislav Petkov <bp@...e.de>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Vince Weaver <vince@...ter.net>, Paul Turner <pjt@...gle.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [RFC 3/6] perf/core: use rb-tree to sched in event groups

On Wed, Jan 11, 2017 at 08:31:11PM +0000, Liang, Kan wrote:

> > Kan, in your per-cpu event list patch you mentioned that you saw a large
> > overhead in perf_iterate_ctx() when skipping events for other CPUs.
> > Which callers of perf_iterate_ctx() specifically was that problematic for? Do
> > those callers only care about the *active* events, for example?
> 
> Based on my test, the large overhead was observed in perf_iterate_sb.
> Yes, it only cares about the *active* events.

Great!

That should mean the first patch of this series (adding the active
events lists) should give us sufficient infrastructure to solve that
particular issue.

Thanks,
Mark.