From: Asias He <asias@redhat.com>
To: Jeff Moyer <jmoyer@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 22:45:58 +0800 [thread overview]
Message-ID: <5006CC26.20203@redhat.com> (raw)
In-Reply-To: <x49fw8pb0ov.fsf@segfault.boston.devel.redhat.com>
On 07/18/2012 10:31 PM, Jeff Moyer wrote:
> 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.
Yes. The iovec's passed in point to userspace buffers. ;-)
--
Asias
next prev parent reply other threads:[~2012-07-18 14:44 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
2012-07-18 14:45 ` Asias He [this message]
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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