From: Dor Laor <dlaor@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk
Date: Mon, 18 Jun 2012 14:14:47 +0300 [thread overview]
Message-ID: <4FDF0DA7.40604@redhat.com> (raw)
In-Reply-To: <87zk81x7dp.fsf@rustcorp.com.au>
On 06/18/2012 01:05 PM, Rusty Russell wrote:
> On Mon, 18 Jun 2012 16:03:23 +0800, Asias He<asias@redhat.com> wrote:
>> On 06/18/2012 03:46 PM, Rusty Russell wrote:
>>> On Mon, 18 Jun 2012 14:53:10 +0800, Asias He<asias@redhat.com> wrote:
>>>> This patch introduces bio-based IO path for virtio-blk.
>>>
>>> Why make it optional?
>>
>> request-based IO path is useful for users who do not want to bypass the
>> IO scheduler in guest kernel, e.g. users using spinning disk. For users
>> using fast disk device, e.g. SSD device, they can use bio-based IO path.
>
> Users using a spinning disk still get IO scheduling in the host though.
> What benefit is there in doing it in the guest as well?
The io scheduler waits for requests to merge and thus batch IOs
together. It's not important w.r.t spinning disks since the host can do
it but it causes much less vmexits which is the key issue for VMs.
>
> Cheers,
> Rusty.
> _______________________________________________
> Virtualization mailing list
> Virtualization@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2012-06-18 11:14 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-18 6:53 [PATCH v2 0/3] Improve virtio-blk performance Asias He
2012-06-18 6:53 ` [PATCH 1/3] block: Introduce __blk_segment_map_sg() helper Asias He
2012-06-18 21:31 ` Tejun Heo
2012-06-19 2:02 ` Asias He
2012-06-19 18:00 ` Tejun Heo
2012-06-18 6:53 ` [PATCH v2 2/3] block: Add blk_bio_map_sg() helper Asias He
2012-06-18 6:53 ` [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk Asias He
2012-06-18 7:46 ` Rusty Russell
2012-06-18 8:03 ` Asias He
2012-06-18 10:05 ` Rusty Russell
2012-06-18 11:14 ` Dor Laor [this message]
2012-06-18 11:39 ` Sasha Levin
2012-06-19 2:51 ` Asias He
2012-06-19 6:21 ` Dor Laor
2012-06-20 4:46 ` Asias He
2012-06-21 9:49 ` Dor Laor
2012-07-01 23:54 ` Rusty Russell
[not found] ` <87r4svxcjw.fsf@rustcorp.com.au>
2012-07-02 2:45 ` Asias He
2012-07-02 6:41 ` Rusty Russell
2012-07-03 0:39 ` Asias He
2012-07-04 2:40 ` Rusty Russell
2012-07-06 1:03 ` Asias He
2012-07-03 13:31 ` Paolo Bonzini
[not found] ` <4FF2F417.2010209@redhat.com>
2012-07-03 14:02 ` Asias He
2012-07-03 14:22 ` Ronen Hod
2012-07-03 14:28 ` Dor Laor
2012-07-04 14:10 ` Paolo Bonzini
2012-06-18 21:28 ` Tejun Heo
2012-06-19 2:39 ` Asias He
2012-06-18 10:13 ` Michael S. Tsirkin
2012-06-19 2:21 ` Asias He
2012-06-18 9:37 ` Stefan Hajnoczi
2012-06-18 10:21 ` Michael S. Tsirkin
2012-06-18 10:45 ` Stefan Hajnoczi
2012-06-19 2:30 ` Asias He
2012-06-18 9:14 ` [PATCH v2 0/3] Improve virtio-blk performance Stefan Hajnoczi
2012-06-18 9:39 ` Asias He
2012-06-18 10:58 ` Stefan Hajnoczi
2012-06-19 4:24 ` Asias He
2012-06-19 10:14 ` Stefan Hajnoczi
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