Re: [PATCH RFC] [X86] Compile Option Os versus O2 on latest x86platform

From: Ingo Molnar
Date: Thu Dec 03 2009 - 10:31:32 EST



* H. Peter Anvin <hpa@xxxxxxxxx> 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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