Re: Some initial thoughts about 2.4

[Sander Vesik <sander_traveling yahoo co uk>]

 --- Daniel Egger <degger fhm edu> wrote: > Am Die, 2002-12-31 um 01.08 schrieb
Sander Vesik:
> 
> > One important thing that it help soptimise is TLB.
> 
> And on which platform? Different architectures have different
> implementations of a TLB which would require another optimisation
> strategy. Trying to squeeze out a 10% startup improvement on a fraction
> of the most commonly used platform where cpu's receive speedups of like
> 10% per month and applications taking milliseconds to start doesn't seem
> to make much sense. 
> Optimizing for yesterdays architecture would be a different thing but
> then again you'll probably not see much negative TLB influences on 
> a Pentium-II or even worse.

I'm not entirely sure what you mean by this - while its true that you want the
reordering to be architecture speific to an extent (so you take page size into 
account) I doubt that you'll find a usefull reordering that took either the tlb
size or associativity into acocunt. many usefull re-orderings (like moving 
frequent caller-calle pairs to be next to each other) are beneficial in any
TLB you are likely to find in a shipping CPU.

> 
> > As for the ordering - its relatively safe bet that you would want to do it 
> > based on call graph information, whetever static call graph or augumented by 
> > say call count information. 
> 
> Well, once could (automatically) gather those information from arc based
> profiling of a big application which heavily uses the toolkit and sort
> of resembles a common denominator.
> 

You may want to use more than one application though.

[snip]

> 
> The argument of having often used functions in the same location to get
> them paged in at once and thus perceive lower startup times seems more
> likely to me than high benefits of shorter lookup times.
> 

The two are complimentary, not exclusive options.

> -- 
> Servus,
>        Daniel
> 

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