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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Date:   Thu, 31 Aug 2017 13:12:40 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
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

Hi,
On 22.08.2017 23:21, Peter Zijlstra wrote:
> 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?

I eventually managed to overcome difficulties with implementation
of rb_tree indexed by {cpu,index} for event groups so please 
see patches v9.

> 
> 
>