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From:   Joonsoo Kim <js1304@gmail.com>
Date:   Tue, 29 Dec 2020 10:10:34 +0900
Message-ID: <CAAmzW4P9OQTh0TYfKUc6Q6z1j0-ewfmOD3c18b9tHPNy0T45hQ@mail.gmail.com>
Subject: Re: [PATCH] mm, slub: Consider rest of partial list if acquire_slab() fails
To:     Jann Horn <jannh@google.com>
Cc:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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2020=EB=85=84 12=EC=9B=94 28=EC=9D=BC (=EC=9B=94) =EC=98=A4=ED=9B=84 10:10,=
 Jann Horn <jannh@google.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> acquire_slab() fails if there is contention on the freelist of the page
> (probably because some other CPU is concurrently freeing an object from t=
he
> page). In that case, it might make sense to look for a different page
> (since there might be more remote frees to the page from other CPUs, and =
we
> don't want contention on struct page).
>
> However, the current code accidentally stops looking at the partial list
> completely in that case. Especially on kernels without CONFIG_NUMA set,
> this means that get_partial() fails and new_slab_objects() falls back to
> new_slab(), allocating new pages. This could lead to an unnecessary
> increase in memory fragmentation.
>
> Fixes: 7ced37197196 ("slub: Acquire_slab() avoid loop")
> Signed-off-by: Jann Horn <jannh@google.com>

Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Thanks.