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

["Carb, Brian A" <Brian.Carb@xxxxxxxxxx>]

Thanks Ryan. We've experienced the wait as well (we contributed the
timeout loop in changeset 10043 for xm-test
01_enforce_dom0_cpus_basic_pos). For some reason, though, vcpu-set is
not releasing procs above #7, even when we wait a long time.


brian carb
unisys corporation - malvern, pa
brian.carb@xxxxxxxxxx
 

-----Original Message-----
From: Ryan Harper [mailto:ryanh@xxxxxxxxxx] 
Sent: Monday, June 12, 2006 11:12 AM
To: Carb, Brian A
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; McAfee, Tommie M; Krysan, Susan;
Puthiyaparambil, Aravindh; Subrahmanian, Raj; Vessey, Bruce A
Subject: Re: [Xen-devel] Unable to set dom0 vcpu to 1

* 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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