From: Dor Laor <dlaor@redhat.com>
To: Ronen Hod <rhod@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Asias He <asias@redhat.com>,
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: Tue, 03 Jul 2012 17:28:12 +0300 [thread overview]
Message-ID: <4FF3017C.4020605@redhat.com> (raw)
In-Reply-To: <4FF3001C.9020706@redhat.com>
On 07/03/2012 05:22 PM, Ronen Hod wrote:
> On 06/18/2012 02:14 PM, Dor Laor wrote:
>> 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.
>
> Does it make sense to use the guest's I/O scheduler at all?
That's the reason we have a noop io scheduler.
> - It is not aware of the physical (spinning) disk layout.
> - It is not aware of all the host's disk pending requests.
> It does have a good side-effect - batching of requests.
>
> Ronen.
>
>>
>>>
>>> Cheers,
>>> Rusty.
>>> _______________________________________________
>>> Virtualization mailing list
>>> Virtualization@lists.linux-foundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
WARNING: multiple messages have this Message-ID (diff)
From: Dor Laor <dlaor@redhat.com>
To: Ronen Hod <rhod@redhat.com>
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: Tue, 03 Jul 2012 17:28:12 +0300 [thread overview]
Message-ID: <4FF3017C.4020605@redhat.com> (raw)
In-Reply-To: <4FF3001C.9020706@redhat.com>
On 07/03/2012 05:22 PM, Ronen Hod wrote:
> On 06/18/2012 02:14 PM, Dor Laor wrote:
>> 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.
>
> Does it make sense to use the guest's I/O scheduler at all?
That's the reason we have a noop io scheduler.
> - It is not aware of the physical (spinning) disk layout.
> - It is not aware of all the host's disk pending requests.
> It does have a good side-effect - batching of requests.
>
> Ronen.
>
>>
>>>
>>> Cheers,
>>> Rusty.
>>> _______________________________________________
>>> Virtualization mailing list
>>> Virtualization@lists.linux-foundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe kvm" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
next prev parent reply other threads:[~2012-07-03 14:28 UTC|newest]
Thread overview: 80+ 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 ` Asias He
2012-06-18 6:53 ` [PATCH 1/3] block: Introduce __blk_segment_map_sg() helper Asias He
2012-06-18 6:53 ` Asias He
2012-06-18 21:31 ` Tejun Heo
2012-06-18 21:31 ` Tejun Heo
2012-06-19 2:02 ` Asias He
2012-06-19 2:02 ` Asias He
2012-06-19 18:00 ` Tejun Heo
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 ` 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 6:53 ` Asias He
2012-06-18 7:46 ` Rusty Russell
2012-06-18 7:46 ` Rusty Russell
2012-06-18 8:03 ` Asias He
2012-06-18 8:03 ` Asias He
2012-06-18 10:05 ` Rusty Russell
2012-06-18 10:05 ` Rusty Russell
2012-06-18 11:14 ` Dor Laor
2012-06-18 11:14 ` Dor Laor
2012-06-18 11:39 ` Sasha Levin
2012-06-18 11:39 ` Sasha Levin
2012-06-19 2:51 ` Asias He
2012-06-19 2:51 ` Asias He
2012-06-19 6:21 ` Dor Laor
2012-06-19 6:21 ` Dor Laor
2012-06-20 4:46 ` Asias He
2012-06-20 4:46 ` Asias He
2012-06-21 9:49 ` Dor Laor
2012-06-21 9:49 ` Dor Laor
2012-07-01 23:54 ` Rusty Russell
2012-07-02 2:45 ` Asias He
2012-07-02 2:45 ` Asias He
2012-07-02 6:41 ` Rusty Russell
2012-07-02 6:41 ` Rusty Russell
2012-07-03 0:39 ` Asias He
2012-07-03 0:39 ` Asias He
2012-07-04 2:40 ` Rusty Russell
2012-07-04 2:40 ` Rusty Russell
2012-07-06 1:03 ` Asias He
2012-07-06 1:03 ` Asias He
2012-07-03 13:31 ` Paolo Bonzini
2012-07-03 13:31 ` Paolo Bonzini
2012-07-03 14:02 ` Asias He
2012-07-03 14:02 ` Asias He
2012-07-01 23:54 ` Rusty Russell
2012-07-03 14:22 ` Ronen Hod
2012-07-03 14:22 ` Ronen Hod
2012-07-03 14:28 ` Dor Laor [this message]
2012-07-03 14:28 ` Dor Laor
2012-07-04 14:10 ` Paolo Bonzini
2012-07-04 14:10 ` Paolo Bonzini
2012-06-18 21:28 ` Tejun Heo
2012-06-18 21:28 ` Tejun Heo
2012-06-19 2:39 ` Asias He
2012-06-19 2:39 ` Asias He
2012-06-18 10:13 ` Michael S. Tsirkin
2012-06-18 10:13 ` Michael S. Tsirkin
2012-06-19 2:21 ` Asias He
2012-06-19 2:21 ` Asias He
2012-06-18 9:37 ` Stefan Hajnoczi
2012-06-18 9:37 ` Stefan Hajnoczi
2012-06-18 10:21 ` Michael S. Tsirkin
2012-06-18 10:21 ` Michael S. Tsirkin
2012-06-18 10:45 ` Stefan Hajnoczi
2012-06-18 10:45 ` Stefan Hajnoczi
2012-06-19 2:30 ` Asias He
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 9:14 ` Stefan Hajnoczi
2012-06-18 9:39 ` Asias He
2012-06-18 9:39 ` Asias He
2012-06-18 10:58 ` Stefan Hajnoczi
2012-06-18 10:58 ` Stefan Hajnoczi
2012-06-19 4:24 ` Asias He
2012-06-19 4:24 ` Asias He
2012-06-19 10:14 ` Stefan Hajnoczi
2012-06-19 10:14 ` Stefan Hajnoczi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4FF3017C.4020605@redhat.com \
--to=dlaor@redhat.com \
--cc=asias@redhat.com \
--cc=hch@lst.de \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=rhod@redhat.com \
--cc=rusty@rustcorp.com.au \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.