Re: [PATCH] mm, page_alloc: Use static global work_struct for draining per-cpu pages
From: Vlastimil Babka
Date: Wed Jan 25 2017 - 04:26:06 EST
On 01/25/2017 09:30 AM, Mel Gorman wrote:
> As suggested by Vlastimil Babka and Tejun Heo, this patch uses a static
> work_struct to co-ordinate the draining of per-cpu pages on the workqueue.
> Only one task can drain at a time but this is better than the previous
> scheme that allowed multiple tasks to send IPIs at a time.
> One consideration is whether parallel requests should synchronise against
> each other. This patch does not synchronise for a global drain as the common
> case for such callers is expected to be multiple parallel direct reclaimers
> competing for pages when the watermark is close to min. Draining the per-cpu
> list is unlikely to make much progress and serialising the drain is of
> dubious merit. Drains are synchonrised for callers such as memory hotplug
> and CMA that care about the drain being complete when the function returns.
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>