linux-kernel - Re: [PATCH 22/63] sched: Favour moving tasks towards the preferred node

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Message-ID: <5252FFFD.4070002@redhat.com>
Date:	Mon, 07 Oct 2013 14:39:57 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 22/63] sched: Favour moving tasks towards the preferred
 node

On 10/07/2013 06:29 AM, Mel Gorman wrote:
> This patch favours moving tasks towards NUMA node that recorded a higher
> number of NUMA faults during active load balancing.  Ideally this is
> self-reinforcing as the longer the task runs on that node, the more faults
> it should incur causing task_numa_placement to keep the task running on that
> node. In reality a big weakness is that the nodes CPUs can be overloaded
> and it would be more efficient to queue tasks on an idle node and migrate
> to the new node. This would require additional smarts in the balancer so
> for now the balancer will simply prefer to place the task on the preferred
> node for a PTE scans which is controlled by the numa_balancing_settle_count
> sysctl. Once the settle_count number of scans has complete the schedule
> is free to place the task on an alternative node if the load is imbalanced.
> 
> [srikar@...ux.vnet.ibm.com: Fixed statistics]
> [peterz@...radead.org: Tunable and use higher faults instead of preferred]
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Acked-by: Rik van Riel <riel@...hat.com>

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