Message-ID: <51B213CB.8070102@yandex-team.ru>
Date: Fri, 07 Jun 2013 21:09:31 +0400
From: Roman Gushchin <klamm@yandex-team.ru>
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To: Christoph Lameter <cl@gentwo.org>
CC: penberg@kernel.org, mpm@selenic.com, yanmin.zhang@intel.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: slub: slab order on multi-processor machines
References: <51B1A04B.7030003@yandex-team.ru> <0000013f1efbaa4f-6039ad3e-286e-4486-8b7e-7b0331edf990-000000@email.amazonses.com>
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On 07.06.2013 18:12, Christoph Lameter wrote:
> On Fri, 7 Jun 2013, Roman Gushchin wrote:
>
>> As I understand, the idea was to make kernel allocations cheaper by reducing
>> the total
>> number of page allocations (allocating 1 page with order 3 is cheaper than
>> allocating
>> 8 1-ordered pages).
>
> Its also affecting allocator speed. By having less page structures to
> manage the metadata effort is reduced. By having more objects in a page
> the fastpath of slub is more likely to be used (Visible in allocator
> benchmarks). Slub can fall back dynamically to order 0 pages if necessary.
> So it can take opportunistically take advantage of contiguous pages.

Thank you for clarification!

May be it's reasonable to fall back to order 0 pages if it's not possible
to allocate new large page without direct compaction?
I'll try to perform some tests here.

Regards,
Roman
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