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Date: Fri, 04 Jul 2014 17:48:07 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] virtio-blk: dataplane: notify guest as
 a batch
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To: Ming Lei <ming.lei@canonical.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Fam Zheng <famz@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Stefan Hajnoczi <stefanha@redhat.com>

Il 04/07/2014 16:52, Ming Lei ha scritto:
>> > What you can do is change notify_guest to something like
>> >
>> >     qemu_bh_schedule(req->dev->dataplane->notify_guest_bh);
>> >
>> > and do the actual notification in the bottom half.  This should ensure that
>> > multiple notifications are coalesced, but it may also introduce new
>> > aio_notify calls even with my patch (a BH scheduled from a BH currently does
>> > an aio_notify; this can be fixed).
> I think we can do better than above because one aio IO completes lots of
> requests, and we just need to notify guest for all these requests.

Exactly, there would be just one BH and thus just one notify.

Paolo