Re: [PATCH v2 for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs

[Joonsoo Kim]

2020년 9월 29일 (화) 오후 1:50, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>님이 작성:
>
> On Tue, 29 Sep 2020 10:28:05 +0900 Joonsoo Kim <js1304@xxxxxxxxx> wrote:
>
> > > What about manually emptying the pcplists beforehand?
> >
> > It also increases the probability. schedule() or interrupt after emptying but
> > before the allocation could invalidate the effect.
>
> Keep local interrupts disabled across the pcp drain and the allocation
> attempt.

As said before, it's an allocation context API and actual allocation
happens later.
Doing such things there is not an easy job.

> > > Or byassing the pcplists for this caller and calling __rmqueue() directly?
> >
> > What this patch does is this one.
>
> I meant via a different function rather than by adding overhead to the
> existing commonly-used function.

Got it. One idea could be disabling/enabling pcp list on these APIs but
it's overhead would not be appropriate on these APIs. I don't have
another idea that doesn't touch the allocation path.

Thanks.