On some production servers with dom0 kernel 2.6.32 pvops and xen 4.0 and domus mainly windows with gplpv I noticed a strange cpu usage by the dom0 mainly with the use of a single cpu, for example this take from one server: xm vcpu-list Name ID VCPU CPU State Time(s) CPU Affinity ... Domain-0 0 0 3 -b- 1043377.5 any cpu Domain-0 0 1 2 r-- 122083.9 any cpu Domain-0 0 2 0 -b- 284636.1 any cpu Domain-0 0 3 1 -b- 80772.9 any cpu ... Note the increased utilisation on the vcpu 0 Domus cpu utilisation apparently successfully distributed but the dom0 has always use more of its vcpu 0 Is this correct or there are bugs on kernel and/or xen? -- View this message in context: http://xen.1045712.n5.nabble.com/Dom0-cpu-utilisation-irregularly-distributed-tp4872878p4872878.html Sent from the Xen - Dev mailing list archive at Nabble.com. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jeremy Fitzhardinge
2011-Oct-05 20:41 UTC
Re: [Xen-devel] Dom0 cpu utilisation irregularly distributed
On 10/05/2011 07:22 AM, Fantu wrote:> On some production servers with dom0 kernel 2.6.32 pvops and xen 4.0 and > domus mainly windows with gplpv I noticed a strange cpu usage by the dom0 > mainly with the use of a single cpu, for example this take from one server: > xm vcpu-list > Name ID VCPU CPU State Time(s) CPU > Affinity > ... > Domain-0 0 0 3 -b- 1043377.5 any cpu > Domain-0 0 1 2 r-- 122083.9 any cpu > Domain-0 0 2 0 -b- 284636.1 any cpu > Domain-0 0 3 1 -b- 80772.9 any cpu > ... > Note the increased utilisation on the vcpu 0 > > Domus cpu utilisation apparently successfully distributed but the dom0 has > always use more of its vcpu 0 > Is this correct or there are bugs on kernel and/or xen?VCPU use is entirely up to the guest kernels. I suspect that cpu0 gets heavier loading because there are a number of things which end up running on cpu 0 by default, such as some kernel threads and interrupts. You can try playing with interrupt migration on dom0 if you like. But balanced CPU use isn''t necessarily a good thing. The kernel will generally avoid migrating processes between CPUs needlessly, so unless you''re actually starved for CPU time, I would expect some VCPUs to be underused compared to others. It probably just means you''ve configured dom0 with too many VCPUs. J _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel