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[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest
From: |
Juan Quintela |
Subject: |
[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts |
Date: |
Wed, 15 Sep 2010 18:10:48 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) |
Anthony Liguori <address@hidden> wrote:
> On 09/12/2010 05:42 AM, Avi Kivity wrote:
>> On 09/11/2010 05:04 PM, Anthony Liguori wrote:
>>> This fixes a couple nasty problems relating to live migration.
>>>
>>> 1) When dealing with shared storage with weak coherence (i.e. NFS),
>>> even if
>>> we re-read, we may end up with undesired caching. By delaying
>>> any reads
>>> until we absolutely have to, we decrease the likelihood of any
>>> undesirable
>>> caching.
>>>
>>> 2) When dealing with copy-on-read, the local storage acts as a
>>> cache. We need
>>> to make sure to avoid any reads to avoid polluting the local cache.
>>>
>>> +
>>> static void ide_identify(IDEState *s)
>>> {
>>> uint16_t *p;
>>> @@ -105,6 +132,8 @@ static void ide_identify(IDEState *s)
>>> return;
>>> }
>>>
>>> + guess_geometry(s);
>>> +
>>
>> This can cause a disk read, no? Shouldn't it be made asynchronous?
>
> Yes, it should. I'm not sure there's an easy way to make it
> asynchronous though not because of the block layer but because of how
> these functions are called.
>
>>
>> Or just move it to just before the guest starts?
>
> We don't really have a notion of "guest starts" today although maybe
> we should.
I agree that we should have more states. Expecting Migration/Migration
done are quite special casses that are handled adhoc now. Having
some state like: NeverRun will make trivial to have vm_start() do the
right thing on the 1st run.
Later, Juan.
> Regards,
>
> Anthony Liguori
- [Qemu-devel] Re: [PATCH 2/3] block-nbd: fix use of protocols in backing files and nbd probing, (continued)
[Qemu-devel] [PATCH 3/3] disk: don't read from disk until the guest starts, Anthony Liguori, 2010/09/11
[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts,
Juan Quintela <=
[Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Kevin Wolf, 2010/09/13
- [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Anthony Liguori, 2010/09/13
- [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Kevin Wolf, 2010/09/13
- [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Anthony Liguori, 2010/09/13
- [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Kevin Wolf, 2010/09/13
- Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Anthony Liguori, 2010/09/13
- Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Avi Kivity, 2010/09/14
- Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Anthony Liguori, 2010/09/14
- Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Avi Kivity, 2010/09/14
Re: [Qemu-devel] Re: [PATCH 3/3] disk: don't read from disk until the guest starts, Stefan Hajnoczi, 2010/09/13