Re: [PATCH 4/4] capture pages freed during direct reclaim for allocationby the reclaimer

[Christoph Lameter]

Andy Whitcroft wrote:
> When a process enters direct reclaim it will expend effort identifying
> and releasing pages in the hope of obtaining a page.  However as these
> pages are released asynchronously there is every possibility that the
> pages will have been consumed by other allocators before the reclaimer
> gets a look in.  This is particularly problematic where the reclaimer is
> attempting to allocate a higher order page.  It is highly likely that
> a parallel allocation will consume lower order constituent pages as we
> release them preventing them coelescing into the higher order page the
> reclaimer desires.

The reclaim problem is due to the pcp queueing right? Could we disable pcp
queueing during reclaim? pcp processing is not necessarily a gain, so
temporarily disabling it should not be a problem.

At the beginning of reclaim just flush all pcp pages and then do not allow pcp
refills again until reclaim is finished?
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