Re: [Qemu-devel] [PATCH RFC] iothread: Add "spawns" property

[Daniel P. Berrange]

On Fri, Nov 04, 2016 at 10:58:04AM +0000, Stefan Hajnoczi wrote:
> On Wed, Oct 19, 2016 at 04:04:50PM +0800, Fam Zheng wrote:
> > The option specifies how many threads to spawn under the iothread
> > object. All threads share the same AioContext so they can safely run
> > (contend) together.
> > 
> > With AioContext going away, the spawns will natually enable the block
> > multi-queue work.
> > 
> > Signed-off-by: Fam Zheng <address@hidden>
> > 
> > ---
> > 
> > Based on v2 of Paolo's RFifoLock removal series, with which the
> > symmetric contention on the single AioContext is no longer a busy
> > preempt loop.
> > ---
> >  include/sysemu/iothread.h |  19 ++++--
> >  iothread.c                | 148 
> > ++++++++++++++++++++++++++++++++++------------
> >  2 files changed, 125 insertions(+), 42 deletions(-)
> 
> I'm not happy with "IOThread" becoming a group of threads.  IOThread
> should stay the way it is.  Instead you should add a new object type
> that simply groups IOThreads for convenient assignment to devices, e.g.
> IOThreadGroup.  Then multiqueue devices can use an IOThreadGroup to work
> inside multiple IOThreads.

Do we even need a IOThreadGroup object ? Can't we just explicitly pass
a list of IOThread object IDs to the device. eg something like

   -device virtio-blk-pci,iothread=t1,iothread=t2,iothread=t3

Regards,
Daniel
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