Messages in this thread | | | Date | Thu, 2 Feb 2017 17:09:16 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH] x86/CPU/AMD: Bring back Compute Unit ID |
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* Borislav Petkov <bp@alien8.de> wrote:
> On Thu, Feb 02, 2017 at 01:10:54PM +0100, Borislav Petkov wrote: > > Now on to run the same thing on a bigger bulldozer. > > It looks differently on the bigger box: > > before: > > Performance counter stats for 'make -s -j17 bzImage' (3 runs): > 143.807894000 seconds time elapsed ( +- 0.89% ) > > Performance counter stats for 'make -s -j17 bzImage' (3 runs): > 147.109189694 seconds time elapsed ( +- 0.49% )
If there's any doubt about the validity of the measurement I'd suggest doing:
perf stat -a --sync --repeat 3 ...
... so that there's no perf overhead and skew from the many processes of a kernel build workload, plus the --sync should reduce IO related noise.
Or:
perf stat --null --sync --repeat 3 ...
... will only measure elapsed time, but will do that very precisely and with very little overhead.
Thanks,
Ingo
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