From: Ingo Molnar <mingo@kernel.org>
To: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Paul Turner <pjt@google.com>,
Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
Christoph Lameter <cl@linux.com>, Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 5/8] sched, numa, mm: Add adaptive NUMA affinity support
Date: Fri, 16 Nov 2012 19:14:33 +0100 [thread overview]
Message-ID: <20121116181433.GA4763@gmail.com> (raw)
In-Reply-To: <50A68096.1050208@redhat.com>
* Rik van Riel <riel@redhat.com> wrote:
> On 11/12/2012 11:04 AM, Peter Zijlstra wrote:
>
> >We change the load-balancer to prefer moving tasks in order of:
> >
> > 1) !numa tasks and numa tasks in the direction of more faults
> > 2) allow !ideal tasks getting worse in the direction of faults
> > 3) allow private tasks to get worse
> > 4) allow shared tasks to get worse
> >
> >This order ensures we prefer increasing memory locality but when
> >we do have to make hard decisions we prefer spreading private
> >over shared, because spreading shared tasks significantly
> >increases the interconnect bandwidth since not all memory can
> >follow.
>
> Combined with the fact that we only turn a certain amount of
> memory into NUMA ptes each second, could this result in a
> program being classified as a private task one second, and a
> shared task a few seconds later?
It's a statistical method, like most of scheduling.
It's as prone to oscillation as tasks are already prone to being
moved spuriously by the load balancer today, due to the per CPU
load average being statistical and them being slightly above or
below a critical load average value.
Higher freq oscillation should not happen normally though, we
dampen these metrics and have per CPU hysteresis.
( We can also add explicit hysteresis if anyone demonstrates
real oscillation with a real workload - wanted to keep it
simple first and change it only as-needed. )
Thanks,
Ingo
next prev parent reply other threads:[~2012-11-16 18:14 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-12 16:04 [PATCH 0/8] Announcement: Enhanced NUMA scheduling with adaptive affinity Peter Zijlstra
2012-11-12 16:04 ` [PATCH 1/8] sched, numa, mm: Introduce sched_feat_numa() Peter Zijlstra
2012-11-12 16:04 ` [PATCH 2/8] sched, numa, mm: Implement THP migration Peter Zijlstra
2012-11-12 16:04 ` [PATCH 3/8] sched, numa, mm: Add credits for NUMA placement Peter Zijlstra
2012-11-12 16:04 ` [PATCH 4/8] sched, numa, mm: Add last_cpu to page flags Peter Zijlstra
2012-11-13 11:55 ` Ingo Molnar
2012-11-13 16:09 ` Rik van Riel
2012-11-12 16:04 ` [PATCH 5/8] sched, numa, mm: Add adaptive NUMA affinity support Peter Zijlstra
2012-11-13 0:02 ` Christoph Lameter
2012-11-13 8:19 ` Ingo Molnar
2012-11-13 22:57 ` Rik van Riel
2012-11-16 18:06 ` Rik van Riel
2012-11-16 18:14 ` Ingo Molnar [this message]
2012-11-16 18:23 ` Rik van Riel
2012-11-29 19:34 ` Andi Kleen
2012-11-12 16:04 ` [PATCH 6/8] sched, numa, mm: Implement constant, per task Working Set Sampling (WSS) rate Peter Zijlstra
2012-11-12 16:04 ` [PATCH 7/8] sched, numa, mm: Count WS scanning against present PTEs, not virtual memory ranges Peter Zijlstra
2012-11-12 16:04 ` [PATCH 8/8] sched, numa, mm: Implement slow start for working set sampling Peter Zijlstra
2012-11-12 18:48 ` Benchmark results: "Enhanced NUMA scheduling with adaptive affinity" Ingo Molnar
2012-11-15 10:08 ` Mel Gorman
2012-11-15 18:52 ` Rik van Riel
2012-11-15 21:27 ` Mel Gorman
2012-11-15 20:32 ` Linus Torvalds
2012-11-15 22:04 ` Rik van Riel
2012-11-16 14:14 ` Mel Gorman
2012-11-16 19:50 ` Andrea Arcangeli
2012-11-16 20:05 ` Mel Gorman
2012-11-16 16:16 ` Ingo Molnar
2012-11-16 15:56 ` Ingo Molnar
2012-11-16 16:25 ` Mel Gorman
2012-11-16 17:49 ` Ingo Molnar
2012-11-16 19:04 ` Mel Gorman
2012-11-12 23:43 ` [PATCH 0/8] Announcement: Enhanced NUMA scheduling with adaptive affinity Christoph Lameter
2012-11-13 7:24 ` Ingo Molnar
2012-11-15 14:26 ` Christoph Lameter
2012-11-16 15:59 ` Ingo Molnar
2012-11-16 20:57 ` Christoph Lameter
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