Messages in this thread | | | Date | Thu, 03 Dec 2009 07:46:18 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH RFC] [X86] Compile Option Os versus O2 on latest x86 platform |
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On 12/03/2009 07:31 AM, Ingo Molnar wrote: > > * H. Peter Anvin <hpa@zytor.com> wrote: > >> On 12/03/2009 07:03 AM, Ma, Ling wrote: >>>> a key question is.. how much more memory do you have free due to -Os? >>>> (because memory is cache is performance on a system level as well) >>> The kernel code size from Os is 12M, that from O2 is 14M. >>>> and how much less icache pressure is there? >>> From perf stat report, cache reference(unified cache) from O2 is almost the same with Os. >> >> The icache pressure was substantially higher (by ~10%) in the reports >> that I saw. > > hm, icache numbers are not included in perf stat runs by default. Are > there some icache numbers i missed perhaps? >
Sorry, you're right; cache references and cache misses. Furthermore, I'm wrong, I was looking at references *per unit time*, which just show that roughly the same number was squeezed into a shorter time.
Never mind me... :-/
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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