linux-kernel - Re: slub: slab order on multi-processor machines

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Message-ID: <51B213CB.8070102@yandex-team.ru>
Date:	Fri, 07 Jun 2013 21:09:31 +0400
From:	Roman Gushchin <klamm@...dex-team.ru>
To:	Christoph Lameter <cl@...two.org>
CC:	penberg@...nel.org, mpm@...enic.com, yanmin.zhang@...el.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: slub: slab order on multi-processor machines

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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