Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S byfast string.

[Ingo Molnar]

* Pavel Machek <pavel@xxxxxx> wrote:

> > Ling, if you are interested, could you send a user-space test-app to 
> > this thread that everyone could just compile and run on various older 
> > boxes, to gather a performance profile of hand-coded versus string ops 
> > performance?
> > 
> > ( And i think we can make a judgement based on cache-hot performance
> >   alone - if then the strings ops will perform comparatively better in
> >   cache-cold scenarios, so the cache-hot numbers would be a conservative
> >   estimate. )
> 
> Ugh, really? I'd expect cache-cold performance to be not helped at all 
> (memory bandwidth limit) and you'll get slow down from additional 
> i-cache misses...

That's my point - the new code is shorter, which will run comparatively 
faster in a cache-cold environment.

	Ingo
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