Re: [PATCH RFC] [X86] Compile Option Os versus O2 on latest x86 platform

[H. Peter Anvin]

On 12/03/2009 07:31 AM, Ingo Molnar wrote:
> 
> * 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?
> 

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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