RE: [Ganglia-developers] hyperthreading & cpu_num patch.

[James M. <Jam...@bi...>]

On SMP machines, each entry in /proc/cpuinfo reports 'core id'
and 'physical id' in addition to 'processor'. The number of
'processor' entries is cpu_count_virtual. The number of distinct
'physical id' entries is the number of CPU packages installed
on the motherboard. The number of distinct 'core id' entries is
the number of CPU cores.

On non-SMP machines, each entry in /proc/cpuinfo reports
'cpu count' (if applicable) to denote how many 'processor'
entries exist for the one physical CPU (i.e., if 'cpu count' is
2, that processor entry is 1/2 of the entries reported for that
1 physical CPU). So the sum of 'processor' entries divided by
their respective 'cpu count' values is the cpu_count_cores and
cpu_count_physical, and the number of 'processor' entries is the
cpu_count_virtual.

It's a little daft, but that's the way it seems to work.

My original patch submission didn't handle the non-SMP case --
I need to fix that.


<Ric...@ba...> wrote on 03/01/2006 12:26:47 PM:

> From the look of /proc/stat and /proc/cpuinfo in cygwin, I am
> not sure how you resolve between virtual and real processors.
> Am I missing something?
> 
> regards,
> richard
> 
> cpu 91283593 0 24818640 2641219155
> cpu0 33563843 0 13294859 1331802093
> cpu1 57719750 0 11523781 1309417062
> page 28101525 3278915
> swap 28101525 3042074
> intr 1021797193
> ctxt 2106977704
> btime 1139854968
> 
> 
> processor       : 0
> vendor_id       : GenuineIntel
> type            : primary processor
> cpu family      : 15
> model           : 2
> model name      :               Intel(R) Pentium(R) 4 CPU 2.80GHz
> stepping        : 9
> brand id        : 9
> cpu count       : 2
> apic id         : 0
> cpu MHz         : 2793
> fpu             : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clfl dtes acpi mmx fxsr sse
> e2 ss htt tmi pbe cid
> processor       : 1
> vendor_id       : GenuineIntel
> type            : primary processor
> cpu family      : 15
> model           : 2
> model name      :               Intel(R) Pentium(R) 4 CPU 2.80GHz
> stepping        : 9
> brand id        : 9
> cpu count       : 2
> apic id         : 1
> cpu MHz         : 2793
> fpu             : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clfl dtes acpi mmx fxsr sse
> e2 ss htt tmi pbe cid
> 
> -----Original Message-----
> From: gan...@li...
> [mailto:gan...@li...] On Behalf Of
> Jason A. Smith
> Sent: 01 March 2006 15:42
> To: James Mcininch
> Cc: Ganglia Developers
> Subject: Re: [Ganglia-developers] hyperthreading & cpu_num patch.
> 
> 
> Hi James,
> 
> As you mentioned in your bug report:
> 
> http://bugzilla.ganglia.info/cgi-bin/bugzilla/show_bug.cgi?id=84
> 
> This has been discussed several times in the mailing lists, like this
> one last year:
> 
> http://sourceforge.net/mailarchive/forum.php?forum_id=7186&max_rows=25&s
> tyle=threaded&viewmonth=200502
> 
> But as the discussion last year confirms, different people might want it
> to work in different ways.  The best solution would probably be to patch
> gmond to report both the number of real and virtual (hyperthreaded) CPUs
> and have a config option in the webfrontend to display the load based on
> one of the two CPU counts.
> 
> ~Jason
> 
> 
> On Wed, 2006-03-01 at 09:40 -0500, James Mcininch wrote:
> > 
> > I want to bring attention to Bugzilla item 84 -- a patch submitted to 
> > fix improper reporting of cpu_num on hyperthreaded Intel processors.
> > 
> > The patch causes it to report the number of CPU cores rather than the 
> > number of virtual CPUs.
> > 
> -- 
> /------------------------------------------------------------------\
> |  Jason A. Smith                          Email:  sm...@bn... |
> |  Atlas Computing Facility, Bldg. 510M    Phone:  (631)344-4226   |
> |  Brookhaven National Lab, P.O. Box 5000  Fax:    (631)344-7616   |
> |  Upton, NY 11973-5000                                            |
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