linux-kernel - Re: [PATCH v2 for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma

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Message-Id: <20200928215055.02ff9b3ff5e0c392b2403411@linux-foundation.org>
Date:   Mon, 28 Sep 2020 21:50:55 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Joonsoo Kim <js1304@...il.com>
Cc:     Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Mel Gorman <mgorman@...hsingularity.net>, kernel-team@....com,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 for v5.9] mm/page_alloc: handle a missing case for
 memalloc_nocma_{save/restore} APIs

On Tue, 29 Sep 2020 10:28:05 +0900 Joonsoo Kim <js1304@...il.com> 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.

> > 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.