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xen-devel
[Xen-devel] [PATCH] Add fallback code to blktap for missing poll-on-aio
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xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] [PATCH] Add fallback code to blktap for missing poll-on-aio support |
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From: |
Mark McLoughlin <markmc@xxxxxxxxxx> |
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Date: |
Thu, 26 Apr 2007 17:50:19 +0100 |
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Thu, 26 Apr 2007 09:49:12 -0700 |
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Red Hat Ltd. Registered Address: Red Hat Ltd, Brian O' Donnell and Partners, 62 Merrion Square, Dublin 2, Ireland. Registered in the Companies Registration Office, Parnell House, 14 Parnell Square, Dublin 1, Ireland, at No. 304873 Directors: Charlie Peters (USA), Michael Cunningham (USA), Brendan Lane |
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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 on 3.0.5 ... unless I'm jinxed :-)
Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
Cheers,
Mark.
xen-blktap-aio-poll-in-thread.patch
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