linux-kernel - Re: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio

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Message-ID: <51F8DE28.4000508@parallels.com>
Date:	Wed, 31 Jul 2013 13:51:36 +0400
From:	Maxim Patlasov <mpatlasov@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Dave Kleikamp <dave.kleikamp@...cle.com>,
	<linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	Zach Brown <zab@...bo.net>
Subject: Re: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec

07/31/2013 01:28 AM, Andrew Morton пишет:
> On Thu, 25 Jul 2013 12:50:26 -0500 Dave Kleikamp <dave.kleikamp@...cle.com> wrote:
>
>> This patch series adds a kernel interface to fs/aio.c so that kernel code can
>> issue concurrent asynchronous IO to file systems.  It adds an aio command and
>> file system methods which specify io memory with pages instead of userspace
>> addresses.
>>
>> This series was written to reduce the current overhead loop imposes by
>> performing synchronus buffered file system IO from a kernel thread.  These
>> patches turn loop into a light weight layer that translates bios into iocbs.
> Do you have any performance numbers?
>
> Does anyone care much about loop performance?  What's the value here?
>
>

OpenVZ uses loopback-device to keep per-container filesystems. We care 
much about overhead introduced by loop: IO-bound applications run on top 
of per-container filesystem shouldn't perform worse than on top of host 
filesystem. So the value for us is zero overhead.

Thanks,
Maxim
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