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Re: [Qemu-devel] KVM call agenda for June 28
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] KVM call agenda for June 28 |
Date: |
Thu, 30 Jun 2011 14:39:41 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 |
Am 30.06.2011 13:48, schrieb Stefan Hajnoczi:
> On Wed, Jun 29, 2011 at 4:41 PM, Marcelo Tosatti <address@hidden> wrote:
>> On Wed, Jun 29, 2011 at 11:08:23AM +0100, Stefan Hajnoczi wrote:
>>> In the future we could add a 'base' argument to block_stream. If base
>>> is specified then data contained in the base image will not be copied.
>>
>> This is a present requirement.
>
> It's not one that I have had in the past but it is a reasonable requirement.
>
> One interesting thing about this requirement is that it makes
> copy-on-read seem like the wrong primitive for image streaming. If
> there is a base image which should not be streamed then a plain loop
> that calls bdrv_is_allocated_chain(bs, base, sector, &pnum) and copies
> sectors into bs is more straightforward than passing base to a
> copy-on-read operation somehow (through a variable that stashes the
> base away somewhere?).
You don't even have to look at the implementation to say that COR is a
useful optimisation. It basically means that you reuse data read by the
guest instead of reading it a second time in your loop. (And this is
equally true for block copy and image streaming)
If this means adding a new field in BlockDriverState, so be it.
Kevin
- [Qemu-devel] KVM call agenda for June 28, Juan Quintela, 2011/06/27
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/06/28
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/06/28
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/06/29
- Re: [Qemu-devel] KVM call agenda for June 28, Kevin Wolf, 2011/06/29
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/06/29
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/06/29
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/06/30
- Re: [Qemu-devel] KVM call agenda for June 28,
Kevin Wolf <=
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/06/30
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/06/30
- Re: [Qemu-devel] KVM call agenda for June 28, Kevin Wolf, 2011/06/30
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/06/30
Re: [Qemu-devel] KVM call agenda for June 28, Anthony Liguori, 2011/06/28