From mboxrd@z Thu Jan  1 00:00:00 1970
From: Maxim Patlasov <mpatlasov@parallels.com>
Subject: Re: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec
Date: Wed, 31 Jul 2013 13:51:36 +0400
Message-ID: <51F8DE28.4000508@parallels.com>
References: <1374774659-13121-1-git-send-email-dave.kleikamp@oracle.com> <20130730142820.313f1af6827276df31913106@linux-foundation.org>
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Cc: Dave Kleikamp <dave.kleikamp@oracle.com>,
	<linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
	Zach Brown <zab@zabbo.net>
To: Andrew Morton <akpm@linux-foundation.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20130730142820.313f1af6827276df31913106@linux-foundation.org>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

07/31/2013 01:28 AM, Andrew Morton =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> On Thu, 25 Jul 2013 12:50:26 -0500 Dave Kleikamp <dave.kleikamp@oracl=
e.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 co=
mmand and
>> file system methods which specify io memory with pages instead of us=
erspace
>> 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 int=
o 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=20
much about overhead introduced by loop: IO-bound applications run on to=
p=20
of per-container filesystem shouldn't perform worse than on top of host=
=20
filesystem. So the value for us is zero overhead.

Thanks,
Maxim