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Date: Tue, 16 Jun 2015 09:39:05 +0100
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20150616083905.GA22299@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 3/3] block: Let bdrv_drain_all() to call
 aio_poll() for each AioContext
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To: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>, qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>


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On Wed, Jun 10, 2015 at 02:38:17PM +0300, Alexander Yarygin wrote:
> After the commit 9b536adc ("block: acquire AioContext in
> bdrv_drain_all()") the aio_poll() function got called for every
> BlockDriverState, in assumption that every device may have its own
> AioContext. If we have thousands of disks attached, there are a lot of
> BlockDriverStates but only a few AioContexts, leading to tons of
> unnecessary aio_poll() calls.
>=20
> This patch changes the bdrv_drain_all() function allowing it find shared
> AioContexts and to call aio_poll() only for unique ones.
>=20
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
> ---
>  block/io.c | 42 ++++++++++++++++++++++++++----------------
>  1 file changed, 26 insertions(+), 16 deletions(-)

Thanks, applied this patch only to my block tree:
https://github.com/stefanha/qemu/commits/block

Patch 2 has a pending issue and Patch 1 is only needed by Patch 2.

Stefan

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