linux-kernel - Re: [PATCH v2 6/7] mm, page_alloc: move draining pcplists to page isolation users

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Date:   Thu, 22 Oct 2020 14:44:32 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        David Hildenbrand <david@...hat.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v2 6/7] mm, page_alloc: move draining pcplists to page
 isolation users

On Thu, Oct 08, 2020 at 01:42:00PM +0200, Vlastimil Babka wrote:
> Currently, pcplists are drained during set_migratetype_isolate() which means
> once per pageblock processed start_isolate_page_range(). This is somewhat
> wasteful. Moreover, the callers might need different guarantees, and the
> draining is currently prone to races and does not guarantee that no page
> from isolated pageblock will end up on the pcplist after the drain.
> 
> Better guarantees are added by later patches and require explicit actions
> by page isolation users that need them. Thus it makes sense to move the
> current imperfect draining to the callers also as a preparation step.
> 
> Suggested-by: David Hildenbrand <david@...hat.com>
> Suggested-by: Pavel Tatashin <pasha.tatashin@...een.com>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Acked-by: Michal Hocko <mhocko@...e.com>

Reviewed-by: Oscar Salvador <osalvador@...e.de>

-- 
Oscar Salvador
SUSE L3