linux-kernel - Re: [PATCH 6/7] mm/page_alloc: Give GFP_ATOMIC and non-blocking allocations access to reserves

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Message-ID: <Y77cikPSHepZ/GQj@dhcp22.suse.cz>
Date:   Wed, 11 Jan 2023 16:58:02 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        NeilBrown <neilb@...e.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] mm/page_alloc: Give GFP_ATOMIC and non-blocking
 allocations access to reserves

On Mon 09-01-23 15:16:30, Mel Gorman wrote:
> Explicit GFP_ATOMIC allocations get flagged ALLOC_HARDER which is a bit
> vague. In preparation for removing __GFP_ATOMIC, give GFP_ATOMIC and
> other non-blocking allocation requests equal access to reserve.  Rename
> ALLOC_HARDER to ALLOC_NON_BLOCK to make it more clear what the flag
> means.

GFP_NOWAIT can be also used for opportunistic allocations which can and
should fail quickly if the memory is tight and more elaborate path
should be taken (e.g. try higher order allocation first but fall back to
smaller request if the memory is fragmented). Do we really want to give
those access to memory reserves as well?
-- 
Michal Hocko
SUSE Labs