From: Jeff Moyer <jmoyer@redhat.com>
To: Asias He <asias@redhat.com>
Cc: linux-kernel@vger.kernel.org,
"Michael S. Tsirkin" <mst@redhat.com>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH RESEND 5/5] vhost-blk: Add vhost-blk support
Date: Wed, 18 Jul 2012 10:31:28 -0400 [thread overview]
Message-ID: <x49fw8pb0ov.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <50060FE8.4040607@redhat.com> (Asias He's message of "Wed, 18 Jul 2012 09:22:48 +0800")
Asias He <asias@redhat.com> writes:
> On 07/18/2012 03:10 AM, Jeff Moyer wrote:
>> Asias He <asias@redhat.com> writes:
>>
>>> vhost-blk is a in kernel virito-blk device accelerator.
>>>
>>> This patch is based on Liu Yuan's implementation with various
>>> improvements and bug fixes. Notably, this patch makes guest notify and
>>> host completion processing in parallel which gives about 60% performance
>>> improvement compared to Liu Yuan's implementation.
>>
>> So, first off, some basic questions. Is it correct to assume that you
>> tested this with buffered I/O (files opened *without* O_DIRECT)?
>> I'm pretty sure that if you used O_DIRECT, you'd run into problems (which
>> are solved by the patch set posted by Shaggy, based on Zach Brown's work
>> of many moons ago). Note that, with buffered I/O, the submission path
>> is NOT asynchronous. So, any speedups you've reported are extremely
>> suspect. ;-)
>
> I always used O_DIRECT to test this patchset. And I mostly used raw
> block device as guest image. Is this the reason why I did not hit the
> problem you mentioned. Btw, I do have run this patchset on image based
> file. I still do not see problems like IO hangs.
Hmm, so do the iovec's passed in point to buffers in userspace? I
thought they were kernel buffers, which would have blown up in
get_user_pages_fast.
Cheers,
Jeff
next prev parent reply other threads:[~2012-07-18 14:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-13 8:55 [PATCH RESEND 0/5] Add vhost-blk support Asias He
2012-07-13 8:55 ` [PATCH RESEND 1/5] aio: Export symbols and struct kiocb_batch for in kernel aio usage Asias He
2012-07-13 8:55 ` [PATCH RESEND 2/5] eventfd: Export symbol eventfd_file_create() Asias He
2012-07-13 8:55 ` [PATCH RESEND 3/5] vhost: Make vhost a separate module Asias He
2012-07-13 8:55 ` [PATCH RESEND 4/5] vhost-net: Use VHOST_NET_FEATURES for vhost-net Asias He
2012-07-13 8:55 ` [PATCH RESEND 5/5] vhost-blk: Add vhost-blk support Asias He
2012-07-17 19:10 ` Jeff Moyer
2012-07-18 1:22 ` Asias He
2012-07-18 14:31 ` Jeff Moyer [this message]
2012-07-18 14:45 ` Asias He
2012-07-19 13:05 ` Anthony Liguori
2012-07-19 13:09 ` Michael S. Tsirkin
2012-07-19 13:09 ` Michael S. Tsirkin
2012-07-20 10:31 ` Stefan Hajnoczi
2012-07-20 20:56 ` Anthony Liguori
2012-07-21 1:07 ` Asias He
2012-07-14 7:49 ` [PATCH RESEND 0/5] " Christoph Hellwig
2012-07-16 9:05 ` Asias He
2012-07-17 15:09 ` Michael S. Tsirkin
2012-07-18 2:09 ` Asias He
2012-07-18 11:42 ` Stefan Hajnoczi
2012-07-20 19:30 ` Michael S. Tsirkin
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