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xen-devel
[Xen-devel] [PATCH][RESEND] Add fallback code to blktap for missing poll
To: |
xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx> |
Subject: |
[Xen-devel] [PATCH][RESEND] Add fallback code to blktap for missing poll-on-aio support |
From: |
Mark McLoughlin <markmc@xxxxxxxxxx> |
Date: |
Mon, 18 Jun 2007 16:36:07 +0100 |
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Mon, 18 Jun 2007 08:34:13 -0700 |
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Hey,
As Stephen explains in this mail:
http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00331.html
blktap requires a xen specific kernel AIO ABI which has been vetoed by
upstream in favour of another approach. Rather than include this ABI,
Fedora has been carrying a patch which makes tap:aio use a thread to
poll for aio events and notify the main thread via a pipe.
The upstream approach of allowing io_getevents() poll normal file
descriptors via epoll is still progressing:
http://lkml.org/lkml/2007/1/3/16
but when that does make it upstream, blktap will require significant
re-working to use that approach.
In the meantime, here's a patch which uses the poll-in-a-thread
approach only if AIO poll support isn't available. It also hides the
details behind a simple abstraction and makes both tap:aio and tap:qcow
use it.
Built and tested with latest xen-unstable.
Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
Cheers,
Mark.
xen-blktap-aio-poll-in-thread.patch
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