Re: [PATCH 13/63] sched: numa: Mitigate chance that same task alwaysupdates PTEs

[Rik van Riel]

On 10/07/2013 06:28 AM, Mel Gorman wrote:
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> 
> With a trace_printk("working\n"); right after the cmpxchg in
> task_numa_work() we can see that of a 4 thread process, its always the
> same task winning the race and doing the protection change.
> 
> This is a problem since the task doing the protection change has a
> penalty for taking faults -- it is busy when marking the PTEs. If its
> always the same task the ->numa_faults[] get severely skewed.
> 
> Avoid this by delaying the task doing the protection change such that
> it is unlikely to win the privilege again.

> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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