Messages in this thread | | | Date | Thu, 3 Dec 2009 16:31:13 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH RFC] [X86] Compile Option Os versus O2 on latest x86 platform |
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* 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?
Ingo
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