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

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Date:	Wed, 31 Jul 2013 10:41:16 +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 8:40 AM, Sedat Dilek <sedat.dilek@...il.com> wrote:
> 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!
>

I have run runltp-lite from latest stable LTP (ltp-full-20130109), but
this reports errors.
I will see later if this happens with a vanilla v3.11-rc3.

See also attached files.

- Sedat -

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

View attachment "dmesg_3.11.0-rc3-1-aio-small.txt" of type "text/plain" (84913 bytes)

Download attachment "config-3.11.0-rc3-1-aio-small" of type "application/octet-stream" (114641 bytes)

Download attachment "runltplite_3.11.0-rc3-1-aio-small.txt.gz" of type "application/x-gzip" (44545 bytes)