On Wednesday, January 25, 2017 4:31 PM 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 <redacted>
---

Acked-by: Hillf Danton <redacted>


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