From: Mel Gorman <mgorman@suse.de>
To: riel@redhat.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
peterz@infradead.org, mingo@redhat.com, chegu_vinod@hp.com
Subject: Re: [PATCH 6/9] numa,sched: normalize faults_cpu stats and weigh by CPU use
Date: Tue, 28 Jan 2014 10:01:31 +0000 [thread overview]
Message-ID: <20140128100131.GS4963@suse.de> (raw)
In-Reply-To: <1390860228-21539-7-git-send-email-riel@redhat.com>
On Mon, Jan 27, 2014 at 05:03:45PM -0500, riel@redhat.com wrote:
> From: Rik van Riel <riel@redhat.com>
>
> Tracing the code that decides the active nodes has made it abundantly clear
> that the naive implementation of the faults_from code has issues.
>
> Specifically, the garbage collector in some workloads will access orders
> of magnitudes more memory than the threads that do all the active work.
> This resulted in the node with the garbage collector being marked the only
> active node in the group.
>
> This issue is avoided if we weigh the statistics by CPU use of each task in
> the numa group, instead of by how many faults each thread has occurred.
>
> To achieve this, we normalize the number of faults to the fraction of faults
> that occurred on each node, and then multiply that fraction by the fraction
> of CPU time the task has used since the last time task_numa_placement was
> invoked.
>
> This way the nodes in the active node mask will be the ones where the tasks
> from the numa group are most actively running, and the influence of eg. the
> garbage collector and other do-little threads is properly minimized.
>
> On a 4 node system, using CPU use statistics calculated over a longer interval
> results in about 1% fewer page migrations with two 32-warehouse specjbb runs
> on a 4 node system, and about 5% fewer page migrations, as well as 1% better
> throughput, with two 8-warehouse specjbb runs, as compared with the shorter
> term statistics kept by the scheduler.
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Chegu Vinod <chegu_vinod@hp.com>
> Signed-off-by: Rik van Riel <riel@redhat.com>
Major changes are related to the weight calculations to avoid overflow
and the avg runtime is calculated based on a longer runtime than the v4
version. Both seem sane so
Acked-by: Mel Gorman <mgorman@suse>
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2014-01-28 10:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-27 22:03 [PATCH v5 0/9] numa,sched,mm: pseudo-interleaving for automatic NUMA balancing riel
2014-01-27 22:03 ` [PATCH 1/9] numa,sched,mm: remove p->numa_migrate_deferred riel
2014-01-27 22:03 ` [PATCH 2/9] rename p->numa_faults to numa_faults_memory riel
2014-01-27 22:03 ` [PATCH 3/9] numa,sched: track from which nodes NUMA faults are triggered riel
2014-01-27 22:03 ` [PATCH 4/9] numa,sched: build per numa_group active node mask from numa_faults_cpu statistics riel
2014-01-27 22:03 ` [PATCH 5/9] numa,sched,mm: use active_nodes nodemask to limit numa migrations riel
2014-01-28 9:58 ` Mel Gorman
2014-01-27 22:03 ` [PATCH 6/9] numa,sched: normalize faults_cpu stats and weigh by CPU use riel
2014-01-28 10:01 ` Mel Gorman [this message]
2014-01-27 22:03 ` [PATCH 7/9] numa,sched: do statistics calculation using local variables only riel
2014-01-27 22:03 ` [PATCH 8/9] numa,sched: rename variables in task_numa_fault riel
2014-01-27 22:03 ` [PATCH 9/9] numa,sched: turn some magic numbers into defines riel
2014-01-28 0:35 ` [PATCH v5 0/9] numa,sched,mm: pseudo-interleaving for automatic NUMA balancing Chegu Vinod
-- strict thread matches above, loose matches on Subject: below --
2014-01-21 22:20 [PATCH v4 0/9] " riel
2014-01-21 22:20 ` [PATCH 6/9] numa,sched: normalize faults_cpu stats and weigh by CPU use riel
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