Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1441657
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: Odd performance results |
| Date | 2016-07-12 21:00 +0200 |
| Message-ID | <rUb4t-o7-7@gated-at.bofh.it> (permalink) |
| References | (1 earlier) <rTfjQ-4IO-5@gated-at.bofh.it> <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> |
| Organization | linux.* mail to news gateway |
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.
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
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
csiph-web