* RE: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
@ 2006-05-09 15:05 Ian Pratt
2006-05-09 15:44 ` Ryan Harper
0 siblings, 1 reply; 6+ messages in thread
From: Ian Pratt @ 2006-05-09 15:05 UTC (permalink / raw)
To: Carb, Brian A, Xen-devel
Cc: Subrahmanian, Raj, Krysan, Susan, Puthiyaparambil, Aravindh,
Vessey, Bruce A
> The comments for dom0-cpus in the xend-config.sxp file
> indicate that setting this value to 0 in an SMP system will
> cause dom0 to use all the available CPUs. However, it appears
> as if setting this value to 0 does not change the number of
> CPUs at all.
>
> I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on
> a Unisys ES7000 with 32 CPUs and 32GB memory. In
> xend-config.sxp, dom0-cpus is set to 0. When xen dom0 boots,
> it is using all 32 procs (as reported by 'grep processor
> /proc/cpuinfo | wc -l').
>
> If I edit the xend-config.sxp file, change the value of
> dom0-cpus to 1, and restart xend, dom0 correctly uses 1 CPUs.
> If I then change dom0-cpus to 0 and restart xend, dom0 still
> uses 1 cpu. The only way to have dom0 use 32 cpus again is to
> either set the value of dom0-cpus to 32, or reboot xen.
>
> Has anyone else seen this behavior?
You can just use the normal xm commands to vary the number of CPUs.
Restarting xend is a rather brutal way of trying to achieve the same
thing...
Ian
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
2006-05-09 15:05 Setting dom0-cpus to 0 doesn't use all cpus asdocumented Ian Pratt
@ 2006-05-09 15:44 ` Ryan Harper
0 siblings, 0 replies; 6+ messages in thread
From: Ryan Harper @ 2006-05-09 15:44 UTC (permalink / raw)
To: Ian Pratt
Cc: Xen-devel, Krysan, Susan, Puthiyaparambil, Aravindh,
Subrahmanian, Raj, Vessey, Bruce A, Carb, Brian A
* Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk> [2006-05-09 10:07]:
> > The comments for dom0-cpus in the xend-config.sxp file
> > indicate that setting this value to 0 in an SMP system will
> > cause dom0 to use all the available CPUs. However, it appears
> > as if setting this value to 0 does not change the number of
> > CPUs at all.
> >
> > I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on
> > a Unisys ES7000 with 32 CPUs and 32GB memory. In
> > xend-config.sxp, dom0-cpus is set to 0. When xen dom0 boots,
> > it is using all 32 procs (as reported by 'grep processor
> > /proc/cpuinfo | wc -l').
> >
> > If I edit the xend-config.sxp file, change the value of
> > dom0-cpus to 1, and restart xend, dom0 correctly uses 1 CPUs.
> > If I then change dom0-cpus to 0 and restart xend, dom0 still
> > uses 1 cpu. The only way to have dom0 use 32 cpus again is to
> > either set the value of dom0-cpus to 32, or reboot xen.
> >
> > Has anyone else seen this behavior?
>
> You can just use the normal xm commands to vary the number of CPUs.
> Restarting xend is a rather brutal way of trying to achieve the same
> thing...
Is it worth keeping dom0-cpus then?
--
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253 T/L: 678-9253
ryanh@us.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
@ 2006-05-09 15:52 Ian Pratt
2006-05-09 16:01 ` Jan Beulich
0 siblings, 1 reply; 6+ messages in thread
From: Ian Pratt @ 2006-05-09 15:52 UTC (permalink / raw)
To: Ryan Harper
Cc: Xen-devel, Krysan, Susan, Puthiyaparambil, Aravindh,
Subrahmanian, Raj, Vessey, Bruce A, Carb, Brian A
> > You can just use the normal xm commands to vary the number of CPUs.
> > Restarting xend is a rather brutal way of trying to achieve
> the same
> > thing...
>
> Is it worth keeping dom0-cpus then?
Yes, it sets it when xend starts.
Ian
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
@ 2006-05-09 15:57 Carb, Brian A
2006-05-09 16:04 ` Ryan Harper
0 siblings, 1 reply; 6+ messages in thread
From: Carb, Brian A @ 2006-05-09 15:57 UTC (permalink / raw)
To: Ryan Harper, Ian Pratt
Cc: Puthiyaparambil, Aravindh, Xen-devel, Krysan, Susan,
Subrahmanian, Raj, Vessey, Bruce A
We discovered this when running the xm-test suite. One of the tests
(01_enforce_dom0_cpus) changes the number of cpus by editing the
xend-config.sxp file and restarting xend. Should this test be updated to
use the method Ian suggested, to vary the number of cpus, rather than
restarting xend?
brian carb (610-648-2437 or N2 385-2437)
unisys cmp technology lab
malvern, pa
brian.carb@unisys.com
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-----Original Message-----
From: Ryan Harper [mailto:ryanh@us.ibm.com]
Sent: Tuesday, May 09, 2006 11:45 AM
To: Ian Pratt
Cc: Carb, Brian A; Xen-devel@lists.xensource.com; Subrahmanian, Raj;
Krysan, Susan; Puthiyaparambil, Aravindh; Vessey, Bruce A
Subject: Re: [Xen-devel] Setting dom0-cpus to 0 doesn't use all cpus
asdocumented
* Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk> [2006-05-09 10:07]:
> > The comments for dom0-cpus in the xend-config.sxp file indicate that
> > setting this value to 0 in an SMP system will cause dom0 to use all
> > the available CPUs. However, it appears as if setting this value to
> > 0 does not change the number of CPUs at all.
> >
> > I'm running SLES10 Beta 11 and xen-unstable changeset 9960 on a
> > Unisys ES7000 with 32 CPUs and 32GB memory. In xend-config.sxp,
> > dom0-cpus is set to 0. When xen dom0 boots, it is using all 32 procs
> > (as reported by 'grep processor /proc/cpuinfo | wc -l').
> >
> > If I edit the xend-config.sxp file, change the value of dom0-cpus to
> > 1, and restart xend, dom0 correctly uses 1 CPUs.
> > If I then change dom0-cpus to 0 and restart xend, dom0 still uses 1
> > cpu. The only way to have dom0 use 32 cpus again is to either set
> > the value of dom0-cpus to 32, or reboot xen.
> >
> > Has anyone else seen this behavior?
>
> You can just use the normal xm commands to vary the number of CPUs.
> Restarting xend is a rather brutal way of trying to achieve the same
> thing...
Is it worth keeping dom0-cpus then?
--
Ryan Harper
Software Engineer; Linux Technology Center IBM Corp., Austin, Tx
(512) 838-9253 T/L: 678-9253
ryanh@us.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
2006-05-09 15:52 Ian Pratt
@ 2006-05-09 16:01 ` Jan Beulich
0 siblings, 0 replies; 6+ messages in thread
From: Jan Beulich @ 2006-05-09 16:01 UTC (permalink / raw)
To: Ian Pratt, Ryan Harper
Cc: Xen-devel, Susan Krysan, Aravindh Puthiyaparambil,
Raj Subrahmanian, Bruce A Vessey, Brian A Carb
>>> "Ian Pratt" <m+Ian.Pratt@cl.cam.ac.uk> 09.05.06 17:52 >>>
>
>> > You can just use the normal xm commands to vary the number of CPUs.
>> > Restarting xend is a rather brutal way of trying to achieve
>> the same
>> > thing...
>>
>> Is it worth keeping dom0-cpus then?
>
>Yes, it sets it when xend starts.
Except when the value is zero. If a previous session lowered the number of VCPUs, then that value will get restored
(from xenstored) rather than using all VCPUs as dom0_vcpus=0 would suggest.
Jan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Setting dom0-cpus to 0 doesn't use all cpus asdocumented
2006-05-09 15:57 Carb, Brian A
@ 2006-05-09 16:04 ` Ryan Harper
0 siblings, 0 replies; 6+ messages in thread
From: Ryan Harper @ 2006-05-09 16:04 UTC (permalink / raw)
To: Carb, Brian A
Cc: Ian Pratt, Xen-devel, Krysan, Susan, Puthiyaparambil, Aravindh,
Subrahmanian, Raj, Vessey, Bruce A
* Carb, Brian A <Brian.Carb@unisys.com> [2006-05-09 10:58]:
> We discovered this when running the xm-test suite. One of the tests
> (01_enforce_dom0_cpus) changes the number of cpus by editing the
> xend-config.sxp file and restarting xend. Should this test be updated to
> use the method Ian suggested, to vary the number of cpus, rather than
> restarting xend?
As Ian said, it is for setting the value when xend starts which is what
the test is about. However, the test should bring dom0 vcpus to the
max and then test enforcement down to 1 rather than assuming that dom0's
current value can be reduced. Or, bail on the test if the current value
of dom0's online vcpus isn't > 2.
--
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253 T/L: 678-9253
ryanh@us.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
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2006-05-09 15:05 Setting dom0-cpus to 0 doesn't use all cpus asdocumented Ian Pratt
2006-05-09 15:44 ` Ryan Harper
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2006-05-09 16:04 ` Ryan Harper
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