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Date: Mon, 30 Jun 2014 14:32:07 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 0/3] block: introduce submit I/O at 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@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

Il 30/06/2014 14:16, Ming Lei ha scritto:
> I added the io queue into AioContext because the io queue can only
> be used in the attached context(or thread), that said the io queue has to
> be put into per context instance.

It doesn't *have* to be per-thread.

It is certainly simplest if you make it per-io_context_t, but this in 
the current code means making it per-BlockDriverState and putting it in 
block/linux-aio.c.

> OK, I will not consider backing_hd case in v1, also the patchset will
> not only improve dataplane, and other devices should benefit from
> it too.
>
> These patches themselves should be simple, and most of code are
> add-only, if bdrv_io_plug()/bdrv_io_unplug() isn't used, they are very close
> to noop.
>
> I just wrote a draft patch to apply the mechanism on virtio-scsi, and
> the improvement is obvious.

I certainly agree.  However, we have to also consider that we're close 
to releasing 2.1.

Paolo