When running a "while : ; do : ; done&" loop in dom0, I saw that none of the guest domains were receiving any CPU time for seconds, quite possibly more than a minute. The guest domains did not get significant CPU time until the inifinite loops in dom0 were terminated. I am currently reading the EDF code to figure out what''s going on, but would appreciate hints that shorten my search... -- All Rights Reversed _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
I found this too when doing a compile in dom0. Search the archives for a thread titled ''Performance problems'' from January this year. Something like: xm sched-sedf <domID> 0 0 0 1 1 was suggested there and it works for me! At a guess, the default scheduling assumes that all of dom0''s work is going to be related to serving data (block and network) to domU''s, so it makes sense to give it priority. James> -----Original Message----- > From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel- > bounces@lists.xensource.com] On Behalf Of Rik van Riel > Sent: Tuesday, 21 February 2006 10:22 > To: xen-devel@lists.xensource.com > Subject: [Xen-devel] dom0 starves guests off CPU > > When running a "while : ; do : ; done&" loop in dom0, I saw that > none of the guest domains were receiving any CPU time for seconds, > quite possibly more than a minute. > > The guest domains did not get significant CPU time until the > inifinite loops in dom0 were terminated. I am currently reading > the EDF code to figure out what''s going on, but would appreciate > hints that shorten my search... > > -- > All Rights Reversed > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 21 Feb 2006, James Harper wrote:> I found this too when doing a compile in dom0. Search the archives for a > thread titled ''Performance problems'' from January this year.Ohhhhh.> At a guess, the default scheduling assumes that all of dom0''s work is > going to be related to serving data (block and network) to domU''s, so it > makes sense to give it priority.That''s not a safe assumption. People will be running CPU intensive things in dom0, if only things like apt-get, yum or recompiling a new package after a security bug was found. Also, some people will want to use dom0 as their desktop, with a few guest domains as test machines... I believe that the default should be safe, even if it''s not the most high performance setting for some configurations. -- All Rights Reversed _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Rik van Riel wrote:> > At a guess, the default scheduling assumes that all of dom0''s work is > > going to be related to serving data (block and network) to domU''s, so it > > makes sense to give it priority. > > That''s not a safe assumption. People will be running CPU > intensive things in dom0, if only things like apt-get, yum > or recompiling a new package after a security bug was found. > > Also, some people will want to use dom0 as their desktop, > with a few guest domains as test machines... > > I believe that the default should be safe, even if it''s not > the most high performance setting for some configurations.Another point. Using dom0 for backup purposes must be common, since you can snapshot the devices that the domUs use. Backups can be long-running CPU-gobbling monsters which you wouldn''t want to shove all your CPU time at just because they happen to sit in dom0... _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel