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Re: [Qemu-devel] dataplane, thread and gpu stuff
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] dataplane, thread and gpu stuff |
Date: |
Tue, 19 Nov 2013 15:20:53 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Nov 18, 2013 at 08:18:47AM -0800, Anthony Liguori wrote:
> On Nov 18, 2013 7:05 AM, "Stefan Hajnoczi" <address@hidden> wrote:
> >
> > On Mon, Nov 18, 2013 at 02:52:53PM +1000, Dave Airlie wrote:
> > > So after talking to a few people at kvm forum I think the GPU code
> > > should probably use the dataplane stuff from the outset,
> > >
> > > The main advantages I think this gives me is being able to dequeue
> > > objects from the vq from a thread and send irq vectors from there as
> > > well.
> > >
> > > Though since it appears the dataplane stuff is kvm specific (at least
> > > the irq handling), I was wondering how I should deal with fallbacks
> > > for non-kvm operation, and quite how much falling back I need to do.
> > >
> > > Can I still use the dataplane/vring code from the normal bottom half
> > > handlers or do I have to write separate code for both situations.
> >
> > As of today, there are still two vring implementations in
> > hw/virtio/virtio.c and hw/virtio/dataplane/vring.c. This means it isn't
> > clean and easy to integrate into a new device yet. Existing dataplane
> > devices basically take advantage of the fact that the non-dataplane
> > version sets up the device before I/O.
>
> I think we also need some form of mdroth's GContext prior to introducing
> more dataplane devices. Sticking every device in a seperate thread with no
> way to control who is where can actually hurt performance. I think we
> really need to have a M-N device thread model too.
Yes, I agree. We need the concept of multiple event loops (QContext).
Stefan