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


From: Peter Lieven
Subject: Re: [Qemu-devel] [PATCH] block/iscsi: introduce bdrv_co_{readv, writev, flush_to_disk}
Date: Mon, 25 Nov 2013 11:56:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1

On 25.11.2013 11:54, Paolo Bonzini wrote:
Il 25/11/2013 11:47, Peter Lieven ha scritto:
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.
Can we proceed with the above patch for 1.8?
Yes, thanks.
Will you pull it or shall I rebase and sent it again after 1.7.0 release?

Peter




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