linux-kernel - Re: [PATCH v7 0/2] perf/core: addressing 4x slowdown during per-process profiling of STREAM benchmark on Intel Xeon Phi

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Message-ID: <20170822202106.GP32112@worktop.programming.kicks-ass.net>
Date:   Tue, 22 Aug 2017 22:21:06 +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>,
        Mark Rutland <mark.rutland@....com>,
        Stephane Eranian <eranian@...gle.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 0/2] perf/core: addressing 4x slowdown during
 per-process profiling of STREAM benchmark on Intel Xeon Phi

On Fri, Aug 18, 2017 at 08:17:15AM +0300, Alexey Budankov wrote:
> Hi,

Please don't post new versions in reply to old versions, that gets them
lost in thread sorted views.

> This patch set v7 moves event groups into rb trees and implements 
> skipping to the current CPU's list on hrtimer interrupt.

Does this depend on your timekeeping rework posted in that v6 thread?
If so, I would have expected to see that as part of these patches, if
not, I'm confused, because part of the problem was that we currently
need to update times for events we don't want to schedule etc..

> Events allocated for the same CPU are still kept in a linked list
> of the event directly attached to the tree because it is unclear 
> how to implement fast iteration thru events allocated for 
> the same CPU when they are all attached to a tree employing 
> additional 64bit index as a secondary treee key.

Finding the CPU subtree and rb_next() wasn't good?