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Date: Tue, 8 Oct 2013 14:39:08 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] block/iscsi: introduce bdrv_co_{readv,
 writev, flush_to_disk}
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: ronniesahlberg@gmail.com, Peter Lieven <pl@kamp.de>, qemu-devel@nongnu.org, stefanha@redhat.com

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.

Kevin