Re: [Qemu-devel] question about concurrent block job

[Zhangleiqiang]

Hi, Stefan:
        Thanks for your relay.

        There are some jobs like drive-mirror, can keep running continuously 
(without --finish/--pivort option ). While the mirroring, we may need to run 
other block jobs, e.g. running block-commit or block-stream to decrease the 
length of the image chain so that the vm's perf can be improved. 
        Although I am also agree that it will require a lot of care, the 
ability for enabling multiple jobs at the same time does make sence under some 
scenario.


> -----Original Message-----
> From: Stefan Hajnoczi [mailto:address@hidden
> Sent: Wednesday, April 24, 2013 9:55 PM
> To: Zhangleiqiang
> Cc: Paolo Bonzini; address@hidden
> Subject: Re: [Qemu-devel] question about concurrent block job
> 
> On Wed, Apr 24, 2013 at 12:28 PM, Zhangleiqiang
> <address@hidden> wrote:
> >         I found qemu does not support concurrently running multiple block
> jobs of the same drive (limited by the bs->in_use field).  But there are 
> indeed
> some type of block job can run concurrently, such as running block stream job
> while running drive mirror, etc.  Am I right ? Is it necessary to introduce 
> the
> concurrency mechanism in qemu ?
> 
> stream and mirror both switch to the destination image file when they
> complete.  I'm not sure it makes sense to run both at the same time.
> Some of the block jobs can interfere with each other, so it's simplest
> to only allow one.

> Enabling multiple jobs at the same time will require a lot of care,
> including extending the HMP/QMP APIs to deal with multiple jobs.
> bs->job is a scalar field at the moment.
> 
> Stefan


----------
Leiqzhang

Best Regards