From: Anthony Liguori <aliguori@us.ibm.com>
To: Kevin Wolf <kwolf@suse.de>
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH] Use qemu_memalign instead of qemu_malloc
Date: Wed, 25 Jun 2008 08:48:13 -0500 [thread overview]
Message-ID: <48624C9D.90903@us.ibm.com> (raw)
In-Reply-To: <48620DAB.5010501@suse.de>
Kevin Wolf wrote:
> Anthony Liguori schrieb:
>
>> I guess the main block code is not as defensive as I thought it was. This patch
>> uses qemu_memalign to allocate the buffers for IO so that you don't get errors
>> when using O_DIRECT.
>>
>
> Actually, the block code should be able to deal with unaligned buffers
> since qemu rev. 4599. This change seems to be present in current KVM.
>
That was what I thought at first too.
> Can you tell exactly which operation failed?
>
The aio requests fail with -22 (EINVAL).
> But apart from that, qemu_memalign is the right thing to do, because
> copying from/into an aligned buffer in the block code costs performance
> (don't know how much, though).
>
Regards,
Anthony Liguori
> Kevin
>
next prev parent reply other threads:[~2008-06-25 13:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-24 18:49 [PATCH] Use qemu_memalign instead of qemu_malloc Anthony Liguori
2008-06-25 9:19 ` Kevin Wolf
2008-06-25 13:48 ` Anthony Liguori [this message]
2008-06-25 14:15 ` Kevin Wolf
2008-06-25 14:19 ` Anthony Liguori
2008-06-25 14:29 ` Kevin Wolf
2008-06-25 15:22 ` Anthony Liguori
2008-06-25 15:29 ` Kevin Wolf
2008-06-25 15:44 ` Anthony Liguori
2008-06-25 14:55 ` Laurent Vivier
2008-06-25 15:14 ` Kevin Wolf
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