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

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Date:	Wed, 31 Jul 2013 08:40:16 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Dave Chinner <david@...morbit.com>,
	Dave Kleikamp <dave.kleikamp@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	"Maxim V. Patlasov" <mpatlasov@...allels.com>,
	Zach Brown <zab@...bo.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec

On Wed, Jul 31, 2013 at 2:43 AM, Dave Chinner <david@...morbit.com> wrote:
> On Tue, Jul 30, 2013 at 02:28:20PM -0700, Andrew Morton wrote:
>> 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?
>>

[ CC Al and Linux-next maintainer ]

The more important question how to test and then provide performance numbers.
If you give me a test-case I give you numbers!

>> Does anyone care much about loop performance?  What's the value here?
>
> Yes. Anyone using loopback devices for file-backed devices exposed
> to containers and VMs cares about the memory and CPU overhead
> the double caching the existing loop device has.
>

Yupp, I am here on Ubuntu/precise AMD64 in a so-called WUBI
environment which makes intensive usage of loopback-device plus FUSE
driver and $fs-of-your-choice (here: ext4).

Today, I have pulled Dave's aio_loop GIT branch into v3.11-rc3.
After successful compilation I am running it right now.

I had also tested v6 of the series [1] from February 2013 and
encouraged Dave to put it into Linux-next [2].
Unfortunately, there was no response from Al.
Again, Dave try to get it into Linux-next!

- Sedat -

[1] http://marc.info/?t=135947707100013&r=1&w=4
[2] http://marc.info/?l=linux-fsdevel&m=136122569807203&w=4
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