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From: Rik van Riel <riel@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH,RFC] numa,sched: use group fault statistics in numa placement
Date: Thu, 01 Aug 2013 12:35:09 -0400	[thread overview]
Message-ID: <51FA8E3D.4070204@redhat.com> (raw)
In-Reply-To: <20130801103713.GO3008@twins.programming.kicks-ass.net>

On 08/01/2013 06:37 AM, Peter Zijlstra wrote:
> On Thu, Aug 01, 2013 at 02:23:19AM -0400, Rik van Riel wrote:
>> Subject: [PATCH,RFC] numa,sched: use group fault statistics in numa placement
>>
>> Here is a quick strawman on how the group fault stuff could be used
>> to help pick the best node for a task. This is likely to be quite
>> suboptimal and in need of tweaking. My main goal is to get this to
>> Peter & Mel before it's breakfast time on their side of the Atlantic...
>>
>> This goes on top of "sched, numa: Use {cpu, pid} to create task groups for shared faults"
>>
>> Enjoy :)
>>
>> +	/*
>> +	 * Should we stay on our own, or move in with the group?
>> +	 * The absolute count of faults may not be useful, but comparing
>> +	 * the fraction of accesses in each top node may give us a hint
>> +	 * where to start looking for a migration target.
>> +	 *
>> +	 *  max_group_faults     max_faults
>> +	 * ------------------ > ------------
>> +	 * total_group_faults   total_faults
>> +	 */
>> +	if (max_group_nid >= 0 && max_group_nid != max_nid) {
>> +		if (max_group_faults * total_faults >
>> +				max_faults * total_group_faults)
>> +			max_nid = max_group_nid;
>> +	}
>
> This makes sense.. another part of the problem, which you might already
> have spotted is selecting a task to swap with.
>
> If you only look at per task faults its often impossible to find a
> suitable swap task because moving you to a more suitable node would
> degrade the other task -- below a patch you've already seen but I
> haven't yet posted because I'm not at all sure its something 'sane' :-)

I did not realize you had not posted that patch yet, and was
actually building on top of it :)

I suspect that comparing both per-task and per-group fault weights
in task_numa_compare should make your code do the right thing in
task_numa_migrate.

I suspect there will be enough randomness in accesses that they
will never be exactly the same, so we might not need an explicit
tie breaker.

However, if numa_migrate_preferred fails, we may want to try
migrating to any node that has a better score than the current
one.  After all, if we have a group of tasks that would fit in
2 NUMA nodes, we don't want half of the tasks to not migrate
at all because the top node is full. We want them to move to
the #2 node at some point.

-- 
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  reply	other threads:[~2013-08-01 16:35 UTC|newest]

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-15 15:20 [PATCH 0/18] Basic scheduler support for automatic NUMA balancing V5 Mel Gorman
2013-07-15 15:20 ` [PATCH 01/18] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman
2013-07-15 15:20 ` [PATCH 02/18] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-07-17 10:50   ` Peter Zijlstra
2013-07-31  7:54     ` Mel Gorman
2013-07-29 10:10   ` Peter Zijlstra
2013-07-31  7:54     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 03/18] mm: numa: Account for THP numa hinting faults on the correct node Mel Gorman
2013-07-17  0:33   ` Hillf Danton
2013-07-17  1:26     ` Wanpeng Li
2013-07-17  1:26     ` Wanpeng Li
2013-07-15 15:20 ` [PATCH 04/18] mm: numa: Do not migrate or account for hinting faults on the zero page Mel Gorman
2013-07-17 11:00   ` Peter Zijlstra
2013-07-31  8:11     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 05/18] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-07-15 15:20 ` [PATCH 06/18] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-07-15 15:20 ` [PATCH 07/18] sched: Favour moving tasks towards the preferred node Mel Gorman
2013-07-25 10:40   ` [PATCH] sched, numa: migrates_degrades_locality() Peter Zijlstra
2013-07-31  8:44     ` Mel Gorman
2013-07-31  8:50       ` Peter Zijlstra
2013-07-15 15:20 ` [PATCH 08/18] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-07-17  1:31   ` Hillf Danton
2013-07-31  9:07     ` Mel Gorman
2013-07-31  9:38       ` Srikar Dronamraju
2013-08-01  4:47   ` Srikar Dronamraju
2013-08-01 15:38     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 09/18] sched: Add infrastructure for split shared/private accounting of NUMA hinting faults Mel Gorman
2013-07-17  2:17   ` Hillf Danton
2013-07-31  9:08     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 10/18] sched: Increase NUMA PTE scanning when a new preferred node is selected Mel Gorman
2013-07-15 15:20 ` [PATCH 11/18] sched: Check current->mm before allocating NUMA faults Mel Gorman
2013-07-15 15:20 ` [PATCH 12/18] sched: Set the scan rate proportional to the size of the task being scanned Mel Gorman
2013-07-15 15:20 ` [PATCH 13/18] mm: numa: Scan pages with elevated page_mapcount Mel Gorman
2013-07-17  5:22   ` Sam Ben
2013-07-31  9:13     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 14/18] sched: Remove check that skips small VMAs Mel Gorman
2013-07-15 15:20 ` [PATCH 15/18] sched: Set preferred NUMA node based on number of private faults Mel Gorman
2013-07-18  1:53   ` [PATCH 15/18] fix compilation with !CONFIG_NUMA_BALANCING Rik van Riel
2013-07-31  9:19     ` Mel Gorman
2013-07-26 11:20   ` [PATCH 15/18] sched: Set preferred NUMA node based on number of private faults Peter Zijlstra
2013-07-31  9:29     ` Mel Gorman
2013-07-31  9:34       ` Peter Zijlstra
2013-07-31 10:10         ` Mel Gorman
2013-07-15 15:20 ` [PATCH 16/18] sched: Avoid overloading CPUs on a preferred NUMA node Mel Gorman
2013-07-15 20:03   ` Peter Zijlstra
2013-07-16  8:23     ` Mel Gorman
2013-07-16 10:35       ` Peter Zijlstra
2013-07-16 15:55   ` Hillf Danton
2013-07-16 16:01     ` Mel Gorman
2013-07-17 10:54   ` Peter Zijlstra
2013-07-31  9:49     ` Mel Gorman
2013-08-01  7:10   ` Srikar Dronamraju
2013-08-01 15:42     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 17/18] sched: Retry migration of tasks to CPU on a preferred node Mel Gorman
2013-07-25 10:33   ` Peter Zijlstra
2013-07-31 10:03     ` Mel Gorman
2013-07-31 10:05       ` Peter Zijlstra
2013-07-31 10:07         ` Mel Gorman
2013-07-25 10:35   ` Peter Zijlstra
2013-08-01  5:13   ` Srikar Dronamraju
2013-08-01 15:46     ` Mel Gorman
2013-07-15 15:20 ` [PATCH 18/18] sched: Swap tasks when reschuling if a CPU on a target node is imbalanced Mel Gorman
2013-07-15 20:11   ` Peter Zijlstra
2013-07-16  9:41     ` Mel Gorman
2013-08-01  4:59   ` Srikar Dronamraju
2013-08-01 15:48     ` Mel Gorman
2013-07-15 20:14 ` [PATCH 0/18] Basic scheduler support for automatic NUMA balancing V5 Peter Zijlstra
2013-07-16 15:10 ` Srikar Dronamraju
2013-07-25 10:36 ` Peter Zijlstra
2013-07-31 10:30   ` Mel Gorman
2013-07-31 10:48     ` Peter Zijlstra
2013-07-31 11:57       ` Mel Gorman
2013-07-31 15:30         ` Peter Zijlstra
2013-07-31 16:11           ` Mel Gorman
2013-07-31 16:39             ` Peter Zijlstra
2013-08-01 15:51               ` Mel Gorman
2013-07-25 10:38 ` [PATCH] mm, numa: Sanitize task_numa_fault() callsites Peter Zijlstra
2013-07-31 11:25   ` Mel Gorman
2013-07-25 10:41 ` [PATCH] sched, numa: Improve scanner Peter Zijlstra
2013-07-25 10:46 ` [PATCH] mm, sched, numa: Create a per-task MPOL_INTERLEAVE policy Peter Zijlstra
2013-07-26  9:55   ` Peter Zijlstra
2013-08-26 16:10     ` Peter Zijlstra
2013-08-26 16:14       ` Peter Zijlstra
2013-07-30 11:24 ` [PATCH] mm, numa: Change page last {nid,pid} into {cpu,pid} Peter Zijlstra
2013-08-01 22:33   ` Rik van Riel
2013-07-30 11:38 ` [PATCH] sched, numa: Use {cpu, pid} to create task groups for shared faults Peter Zijlstra
2013-07-31 15:07   ` Peter Zijlstra
2013-07-31 15:38     ` Peter Zijlstra
2013-07-31 15:45     ` Don Morris
2013-07-31 16:05       ` Peter Zijlstra
2013-08-02 16:47       ` [PATCH -v3] " Peter Zijlstra
2013-08-02 16:50         ` [PATCH] mm, numa: Do not group on RO pages Peter Zijlstra
2013-08-02 19:56           ` Peter Zijlstra
2013-08-05 19:36           ` [PATCH] numa,sched: use group fault statistics in numa placement Rik van Riel
2013-08-09 13:55             ` Don Morris
2013-08-28 16:41         ` [PATCH -v3] sched, numa: Use {cpu, pid} to create task groups for shared faults Peter Zijlstra
2013-08-28 17:10           ` Rik van Riel
2013-08-01  6:23   ` [PATCH,RFC] numa,sched: use group fault statistics in numa placement Rik van Riel
2013-08-01 10:37     ` Peter Zijlstra
2013-08-01 16:35       ` Rik van Riel [this message]
2013-08-01 22:36   ` [RFC PATCH -v2] " Rik van Riel
2013-07-30 13:58 ` [PATCH 0/18] Basic scheduler support for automatic NUMA balancing V5 Andrew Theurer

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