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Groups > linux.kernel > #1441681
| From | "Dr. David Alan Gilbert" <dave@treblig.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [CRM114spam]: Re: Odd performance results |
| Date | 2016-07-12 21:40 +0200 |
| Message-ID | <rUbHb-S4-19@gated-at.bofh.it> (permalink) |
| References | (2 earlier) <rTods-1VQ-7@gated-at.bofh.it> <rU7kd-6jl-5@gated-at.bofh.it> <rU7tU-6CN-19@gated-at.bofh.it> <rUa8q-8da-19@gated-at.bofh.it> <rUb4t-o7-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
* Peter Zijlstra (peterz@infradead.org) wrote:
> On Tue, Jul 12, 2016 at 10:49:58AM -0700, H. Peter Anvin wrote:
> > On 07/12/16 08:05, Paul E. McKenney wrote:
> > The CPU in question (and /proc/cpuinfo should show this) has four cores
> > with a total of eight threads. The "siblings" and "cpu cores" fields in
> > /proc/cpuinfo should show the same thing. So I am utterly confused
> > about what is unexpected here?
>
> Typically threads are enumerated differently on Intel parts. Namely:
>
> cpu_id = code_id + nr_cores * smt_id
>
> which gives, for a 4 core, 2 thread part:
>
> 0-3: core 0-3, smt0
> 4-7: core 0-3, smt1
>
> My Core i7-2600k for example has:
>
> $ cat /sys/devices/system/cpu/cpu*/topology/thread_siblings_list
> 0,4
> 1,5
> 2,6
> 3,7
> 0,4
> 1,5
> 2,6
> 3,7
>
> The ordering Paul has, namely 0,1 for core0,smt{0,1} is not something
> I've ever seen on an Intel part. AMD otoh does enumerate their CMT stuff
> like what Paul has.
Paul's isn't unique:
cat /sys/devices/system/cpu/cpu*/topology/thread_siblings_list
0-1
0-1
2-3
2-3
i7-3520M CPU @ 2.90GHz (Dual core with hyperthread, Thinkpad t530, fedora 24)
Dave
--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
\ _________________________|_____ http://www.treblig.org |_______/
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Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-10 06:30 +0200
Re: Odd performance results Peter Zijlstra <peterz@infradead.org> - 2016-07-10 07:20 +0200
Re: Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-10 16:50 +0200
Re: Odd performance results Peter Zijlstra <peterz@infradead.org> - 2016-07-12 17:00 +0200
Re: Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-12 17:10 +0200
Re: Odd performance results "H. Peter Anvin" <hpa@zytor.com> - 2016-07-12 20:00 +0200
Re: Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-12 20:30 +0200
Re: Odd performance results Peter Zijlstra <peterz@infradead.org> - 2016-07-12 21:00 +0200
Re: [CRM114spam]: Re: Odd performance results "Dr. David Alan Gilbert" <dave@treblig.org> - 2016-07-12 21:40 +0200
Re: [CRM114spam]: Re: Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-12 22:10 +0200
Re: [CRM114spam]: Re: Odd performance results Ingo Molnar <mingo@kernel.org> - 2016-07-13 09:30 +0200
Re: Odd performance results Ingo Molnar <mingo@kernel.org> - 2016-07-13 09:20 +0200
Re: Odd performance results Henrique de Moraes Holschuh <hmh@hmh.eng.br> - 2016-07-13 14:40 +0200
Re: Odd performance results Peter Zijlstra <peterz@infradead.org> - 2016-07-13 14:40 +0200
Re: Odd performance results "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-13 16:10 +0200
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