linux-kernel - Re: [PATCH v4 2/4] mm: failfast mode with __GFP_NORETRY in alloc_contig

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Date:   Mon, 25 Jan 2021 14:13:43 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, hyesoo.yu@...sung.com,
        david@...hat.com, surenb@...gle.com, pullip.cho@...sung.com,
        joaodias@...gle.com, hridya@...gle.com, john.stultz@...aro.org,
        sumit.semwal@...aro.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, hch@...radead.org, robh+dt@...nel.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v4 2/4] mm: failfast mode with __GFP_NORETRY in
 alloc_contig_range

On Mon 25-01-21 14:12:02, Michal Hocko wrote:
> On Thu 21-01-21 09:55:00, Minchan Kim wrote:
> > Contiguous memory allocation can be stalled due to waiting
> > on page writeback and/or page lock which causes unpredictable
> > delay. It's a unavoidable cost for the requestor to get *big*
> > contiguous memory but it's expensive for *small* contiguous
> > memory(e.g., order-4) because caller could retry the request
> > in different range where would have easy migratable pages
> > without stalling.
> > 
> > This patch introduce __GFP_NORETRY as compaction gfp_mask in
> > alloc_contig_range so it will fail fast without blocking
> > when it encounters pages needed waiting.
> 
> I am not against controling how hard this allocator tries with gfp mask
> but this changelog is rather void on any data and any user.

OK, I can see that a user is in the last patch.

-- 
Michal Hocko
SUSE Labs