[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [patch 6/7] QEMU live block copy
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] [patch 6/7] QEMU live block copy |
Date: |
Wed, 15 Jun 2011 13:59:04 -0300 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Jun 07, 2011 at 01:15:02PM +0100, Stefan Hajnoczi wrote:
> On Mon, Jun 6, 2011 at 5:55 PM, Marcelo Tosatti <address@hidden> wrote:
>
> I haven't reviewed this whole patch yet, but comments below.
>
> This patch, like image streaming, may hit deadlocks due to synchronous
> I/O emulation. I discovered this problem when working on image
> streaming and it should be solved by getting rid of the asynchronous
> context concept. The problem is that async I/O emulation will push a
> new context, preventing existing requests to complete until the
> current context is popped again. If the image format has dependencies
> between requests (e.g. QED allocating writes are serialized), then
> this leads to deadlock because the new request cannot complete until
> the old one does, but the old one needs to wait for the context to be
> popped. I think you are not affected by the QED allocating write case
> since the source image is only read, not written, by live block copy.
> But you might encounter this problem in other places.
I see. This should be fixed in the context push/pop logic (or something
equivalent), as you mention.
Fixed other comments, thanks.
- [Qemu-devel] [patch 7/7] do not allow migration if block copy in progress, (continued)
- Re: [Qemu-devel] [patch 6/7] QEMU live block copy,
Marcelo Tosatti <=
[Qemu-devel] [patch 5/7] Add vmstop code for live block copy, Marcelo Tosatti, 2011/06/06
[Qemu-devel] [patch 3/7] Add error messages for live block copy, Marcelo Tosatti, 2011/06/06
[Qemu-devel] [patch 4/7] Add blkdebug points for live block copy, Marcelo Tosatti, 2011/06/06
[Qemu-devel] [patch 2/7] Add blkmirror block driver, Marcelo Tosatti, 2011/06/06
[Qemu-devel] [patch 1/7] add migration_active function, Marcelo Tosatti, 2011/06/06