linux-kernel - Re: [PATCH 0/9] re-shrink 'struct page' when SLUB is on.

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Message-ID: <52D41F52.5020805@sr71.net>
Date:	Mon, 13 Jan 2014 09:16:02 -0800
From:	Dave Hansen <dave@...1.net>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Christoph Lameter <cl@...ux.com>
CC:	Pekka Enberg <penberg@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/9] re-shrink 'struct page' when SLUB is on.

On 01/12/2014 05:44 PM, Joonsoo Kim wrote:
> We only touch one struct page on small allocation.
> In 64-byte case, we always use one cacheline for touching struct page, since
> it is aligned to cacheline size. However, in 56-byte case, we possibly use
> two cachelines because struct page isn't aligned to cacheline size.

I think you're completely correct that this can _happen_, but I'm a bit
unconvinced that what you're talking about is the thing which dominates
the results.  I'm sure it plays a role, but the tests I was doing were
doing tens of millions of allocations and touching a _lot_ of 'struct
pages'.  I would not expect these effects to be observable across such a
large sample of pages.
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