linux-kernel - Re: [PATCH 09/19] sched/numa: Modify migrate

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Date:   Tue, 5 Jun 2018 09:58:40 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 09/19] sched/numa: Modify migrate_swap to accept
 additional params

On Mon, Jun 04, 2018 at 03:30:18PM +0530, Srikar Dronamraju wrote:
> There are checks in migrate_swap_stop that check if the task/cpu
> combination is as per migrate_swap_arg before migrating.
> 
> However atleast one of the two tasks to be swapped by migrate_swap could
> have migrated to a completely different cpu before updating the
> migrate_swap_arg. The new cpu where the task is currently running could
> be a different node too. If the task has migrated, numa balancer might
> end up placing a task in a wrong node.  Instead of achieving node
> consolidation, it may end up spreading the load across nodes.
> 
> To avoid that pass the cpus as additional parameters.
> 
> While here, place migrate_swap under CONFIG_NUMA_BALANCING.
> 
> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Acked-by: Mel Gorman <mgorman@...hsingularity.net>

-- 
Mel Gorman
SUSE Labs