From: Christoph Lameter <cl@linux-foundation.org>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eric Sandeen <sandeen@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, mhalcrow@us.ibm.com,
stable@kernel.org
Subject: Re: [PATCH] eCryptfs - use page_alloc not kmalloc to get a page of memory
Date: Wed, 30 Jul 2008 09:48:41 -0500 [thread overview]
Message-ID: <48907F49.7020101@linux-foundation.org> (raw)
In-Reply-To: <488E3643.8000300@cs.helsinki.fi>
Pekka Enberg wrote:
>> For whatever reason, I did see non-page-aligned memory returned from
>> kmalloc(PAGE_CACHE_SIZE), and I think this is what caused the problem
>> once virt_to_page() was used to get hold of a page to pass around in the
>> ecryptfs/crypto code...
>
> With SLUB? I can't see how that's possible. I can see this with SLAB,
> though, for 4K pages.
It possible because PAGE_CACHE_SIZE is still handled by SLUB and if debugging is on then kmalloc may return non page aligned objects. The handoff to the page allocator only occurs for objects > 4k. We used to do this also for 4k objects but then we got performance regressions in tbench.
> In any case, the patch, of course, make sense as kmalloc() behavior
> varies between allocators.
>
> Pekka
next prev parent reply other threads:[~2008-07-30 14:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-28 16:13 [PATCH] eCryptfs - use page_alloc not kmalloc to get a page of memory Eric Sandeen
2008-07-28 16:25 ` Michael Halcrow
2008-07-28 16:53 ` Rik van Riel
2008-07-28 20:35 ` Andrew Morton
2008-07-28 20:38 ` Eric Sandeen
2008-07-28 20:42 ` Pekka Enberg
2008-07-28 21:03 ` Eric Sandeen
2008-07-28 21:12 ` Pekka Enberg
2008-07-30 14:48 ` Christoph Lameter [this message]
2008-07-30 14:39 ` Christoph Lameter
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