[Xen-devel] PATCH: Reduce xenstore transactions when listing domains

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

This is a followup to patches I've posted a couple of times before:

http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00487.html
http://lists.xensource.com/archives/html/xen-devel/2007-04/msg00663.html


In summary, this allows a xenstore transaction object to be passed around
the various device controllers, so that they don't have todo lots of 
singletone transactions. Transactions have very heavy I/O impact from
xenstored so reducing their number is important. 

When running 3 guests, this patch reduces the impact of 'xm list --long'
from 176 transactions, scaling O(n) with guests, to 26 transactions
with O(1) scaling.

I have previously attempted to also address the same issue with 'xm create'
but that's much harder since the device front/back handshake requires that
XenD use a number of small transactions. So i've not changed anything here.

I have now been running this patch in Fedora builds of Xen for many months
with no reported regressions, so I think its stable enough to be merged
now.

  Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>

Dan.
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Attachment: xen-xs-transactions.patch
Description: Text document

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