Re: [Xen-devel] Unable to set dom0 vcpu to 1

[Ryan Harper <ryanh@xxxxxxxxxx>]

* Carb, Brian A <Brian.Carb@xxxxxxxxxx> [2006-06-08 15:13]:
> > Running xen-unstable changeset 10269 on a Unisys ES7000/one, x86_64,
> > 16 procs, 16 GB RAM under SLES 10 RC1. 
> > 
> > At startup, dom0-cpus is set to 0 (the default) in the xend-config.sxp
> > file, and dom0 uses all 16 cpus. 'xm top' shows 16 procs, 'xm list'
> > shows dom0 using 16 cpus, and 'xm vcpu-list' shows 16 cpus assigned to
> > dom0.
> > 
> > When we try to reduce the procs for dom0 to 1 using 'xm vcpu-set 0 1',
> > the number of procs, as shown by /proc/cpuinfo, reduces to 9. 'xm
> > list' shows dom0 using 9 procs, and 'xm vcpu-list' shows that procs
> > 1-7 have been released, while procs 0 and 8 through 15 are still
> > assigned. Nothing is shown on the serial port.
> > 
> > Can anyone shed some light on why the rest of the procs might not be
> > released? Thanks.

On large smp boxes, it takes some time to unplug all of the processors as any
processes that are running on those cpus have to be migrated to another cpu.
On a 32-way, it took 15 seconds to go from 32 to 1.  As I ran xm list, you can
see the number of active vcpus reduce over time.

[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    21 r-----  4494.6
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    19 r-----  4495.4
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    17 r-----  4496.2
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    16 r-----  4496.8
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    16 r-----  4497.4
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    15 r-----  4497.6
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    14 r-----  4498.1
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    13 r-----  4498.6
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    12 r-----  4499.2
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    12 r-----  4499.4
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    10 r-----  4500.3
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507    10 r-----  4500.7
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     9 r-----  4501.0
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     8 r-----  4501.5
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     7 r-----  4502.0
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     6 r-----  4502.5
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     4 r-----  4503.4
[root@x460-3 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      507     1 r-----  4504.4


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh@xxxxxxxxxx

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