linux-kernel - Re: [PATCH v2]: perf/core: addressing 4x slowdown during per-process, profiling of STREAM benchmark on Intel Xeon Phi

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Message-ID: <20170529112311.ht3pg2dd7pjm3m3a@hirez.programming.kicks-ass.net>
Date:   Mon, 29 May 2017 13:23:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Dmitri Prokhorov <Dmitry.Prohorov@...el.com>,
        Valery Cherepennikov <valery.cherepennikov@...el.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2]: perf/core: addressing 4x slowdown during
 per-process, profiling of STREAM benchmark on Intel Xeon Phi

On Mon, May 29, 2017 at 01:56:05PM +0300, Alexey Budankov wrote:
> On 29.05.2017 13:43, Peter Zijlstra wrote:

> > Why can't the tree do both?
> > 
> 
> Well, indeed, the tree provides such capability too. However switching to
> the full tree iteration in cases where we now go through _groups lists will
> enlarge the patch, what is probably is not a big deal. Do you think it is
> worth implementing the switch?

Do it as a series of patches, where patch 1 introduces the tree, patches
2 through n convert the list users into tree users, and patch n+1
removes the list.

I think its good to not have duplicate data structures if we can avoid
it.