Re: [Qemu-devel] [PATCH 10/15] linux-aio: increase max event to 256

[Stefan Hajnoczi]

On Thu, Jul 31, 2014 at 01:20:22AM +0800, Ming Lei wrote:
> On Wed, Jul 30, 2014 at 10:00 PM, Paolo Bonzini <address@hidden> wrote:
> > Il 30/07/2014 13:39, Ming Lei ha scritto:
> >> This patch increases max event to 256 for the comming
> >> virtio-blk multi virtqueue support.
> >>
> >> Signed-off-by: Ming Lei <address@hidden>
> >> ---
> >>  block/linux-aio.c |    2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > What makes the new magic number less magic than the old one?
> 
> Just for supporting the coming multi virtqueue, otherwise it is
> easy to trigger EAGAIN.
> 
> Or do you have better idea to figure out a non-magic number?

The virtio-blk device knows how many requests can be in-flight at a
time.  laio_init() could take a size parameter.  The messy thing is that
the block layer is between the virtio-blk device and Linux AIO, so we'd
need to pass that information down.

Stefan

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