SCHED_ULE vs SCHED_4BSD for XENHVM domU
danilobaio at gmail.com
Fri Oct 30 18:17:25 UTC 2009
On Thu, Oct 29, 2009 at 9:12 PM, Carsten Heesch <carsten at ossafe.org> wrote:
> Hi guys,
> After FreeBSD 8.0-RC2 is working well (for me) on Xen 3.3.1, I somehow made
> an interesting observation:
> Even if the FreeBSD domU does absolutely nothing, each of the assigned
> vCPUs will be reported by xentop as using 15%-25% CPU time. It doesn't
> matter, if domU is running with 1 or 4 vCPUs. All of them float at the same
> On the same Xen box five other domU's (CentOS 5.2-5.4) have an idle CPU
> percentage of 0 to 0.5%.
> So I played a bit and figured out that changing the scheduler in the XENHVM
> kernel configuration from "option SCHED_ULE" to "option SCHED_4BSD" resolves
> this problem. The idle state of the FreeBSD domU is now identical to the
> CentOS domU's.
> However, this of course means using an old (maybe even deprecated?)
> scheduler, which moreover isn't the best choice for multiple (virtual)
> The configuration I tested on is:
> Intel i7 920 Quad-Core with Hyperthreading (8 logical CPUs)
> Citrix XenServer 5.5 (based on CentOS 5.2, Xen 3.3.1)
> Any thoughts, ideas, solutions?
Same thing here.
I've build 8.0-RC2 amd64 with kernel XENHVM for testing with a XenServer
5.0.0 that i have here.
Only the memory information don't appear on the console of xencenter.
And the processor 14% of use all the time.
After build with SCHED_4BSD, 3% usage CPU.
AMD64 - XENHVM
freeba8# uname -a
FreeBSD freeba8.localdomain 8.0-RC2 FreeBSD 8.0-RC2 #0: Fri Oct 30 15:18:43
BRST 2009 root at freeba8.localdomain:/usr/obj/usr/src/sys/XENHVM amd64
XenServer 5.0.0 (CentOS)
Danilo Gonçalves Baio (dbaio)
danilobaio (*) gmail . com
+55 (44) 8801 1257
More information about the freebsd-xen