From: "Zhang Haoyu" <zhanghy@sangfor.com>
To: "Marcus White" <roastedseaweed.k@gmail.com>
Cc: kvm <kvm@vger.kernel.org>
Subject: Re: Some more basic questions..
Date: Tue, 3 Jun 2014 14:47:11 +0800 [thread overview]
Message-ID: <201406031447098993964@sangfor.com> (raw)
In-Reply-To: CALAJOd37Jr5v_H2LdjC0ix9Hs+Y76EOgZkA9g9rat8zsyX=7gw@mail.gmail.com
>>>1. If IO to a block device goes through QEMU and not vhost, are there
>>>data copies between kernel and user mode if I do IO to a block device
>>>or is it zero copy? Kind of related to Question (2) also.
>>>
>> I'm not sure, it perhaps depend on which IO mode you chose, qemu pthreads IO, or linux AIO?
>> Somebody else do a favour, please.
>
>That would be definitely good to know:) I didnt know about the modes
>as such. Can you clarify? Are you talking about vhost-LIO vs Qemu? The
>LIO part, I do believe, is zero copy..
>I have seen pretty high memory usage on QEMU thread, not sure why.
>
Sorry for my poor knowledge about block subsystem.
I don't know about vhost-LIO, do you mean vhost-blk or vhost-scsi?
Linux AIO what I said above is the linux native aio, which only works for uncached access(O_DIRECT), qemu main-thread use it to do block IO,
qemu pthreads IO means that qemu creates dedicated threads to do block IO job.
next prev parent reply other threads:[~2014-06-03 6:47 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-28 20:59 Some more basic questions Marcus White
2014-05-29 6:04 ` Venkateswara Rao Nandigam
2014-05-29 6:45 ` Zhang Haoyu
2014-05-30 4:06 ` Marcus White
2014-05-30 6:48 ` Zhang Haoyu
2014-06-02 21:19 ` Marcus White
2014-06-03 3:43 ` Zhang Haoyu
2014-06-03 4:53 ` Marcus White
2014-06-03 6:47 ` Zhang Haoyu [this message]
2014-06-03 6:54 ` Venkateswara Rao Nandigam
2014-06-03 11:00 ` Zhang Haoyu
2014-06-03 11:25 ` Venkateswara Rao Nandigam
2014-06-04 1:08 ` Marcus White
2014-06-05 4:42 ` Marcus White
2014-06-12 18:48 ` Marcus White
2014-06-03 12:51 ` Zhang Haoyu
-- strict thread matches above, loose matches on Subject: below --
2003-11-10 4:15 Alejandro Sanchez Acosta
2003-11-10 12:17 ` Alex Zarochentsev
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