Re: [Qemu-devel] [PATCH] block/iscsi: introduce bdrv_co_{readv, writev, flush_to_disk}

[Peter Lieven]

On 08.10.2013 14:39, Kevin Wolf wrote:
> Am 08.10.2013 um 14:35 hat Paolo Bonzini geschrieben:
> > Il 08/10/2013 14:33, Kevin Wolf ha scritto:
> > > > > > > this converts read, write and flush functions from aio to coroutines.
> > > > > I'm not sure it's already the time for this...  Cancellation sucks in
> > > > > QEMU, and this is going to make things even worse.
> > > Not sure what you're referring to. If you mean iscsi_aio_cancel(), isn't
> > > it dead code anyway since we changed block.c to use coroutines for
> > > everything? bdrv_co_io_em() even throws the acb away, so even if you
> > > wanted, there's no way to cancel the request even today.
> > SCSI tries to use cancellation, and this results in VCPU threads
> > starving all other threads.  So I would like to introduce cancellation
> > points for coroutines.
> Sounds like a nice thing to have, but it's unrelated to this patch.
> Cancellation means waiting for request completion before and after the
> patch.
Is there anything I can contribute or is this all outside the iscsi driver?