Features/ArchitectureSupport - changing what we build for

[William Cohen]

Kevin Kofler wrote:
> Callum Lerwick wrote:
>> Going -O3 rather than -O2 is going to make a bigger difference than
>> anything else. If you want to improve performance, you need to run
>> profiles, locate performance critical bits of code, figure out if -O3 is
>> beneficial, and/or write some hand tuned assembly/intrinsic code.
>>
>> Not to mention, the biggest performance problem on modern processors is
>> memory. Minimizing cache thrashing is way more important than what
>> instructions you use. Optimize data structures before code.
> 
> That's actually an argument for investigating -Os, not -O3.
> 
>         Kevin Kofler
> 

In 2004 there were some experiments performed by some NCSU students on the
effect of -Os on code size and performance:

people.redhat.com/wcohen/ncsu2004/Space%20Optimizations.pdf

There was some minor reductions in cache misses, major page faults, and startup
times for the mozilla application.

-Will