How much is known about -Os on X86_64?

[William Cohen]

Steve Bergman wrote:
> I have a few questions.  How much work has been done to benchmark the 
> advantages/disadvantages of using -Os for various FC packages on 
> X86_64?  I know that on x86 -Os is used fort he kernel.  On X86_64, it 
> looks to me like -Os is not used.  In fact, it seems that I read 
> somewhere that one should not use -Os on X86_64, or shouldn't use it on 
> the kernel, or shouldn't use it in FC4, or something like that and I 
> can't seem to relocate that reference.  Anyone know anything about that?
> 
> Also, how useful would it be if  did some real world benchmarking on my 
> Athlon64 2800+ system running FC4/X86_64?  Would I be wasting my time, 
> duplicating someone else's previous efforts?  What packages might 
> benefit?  Is it possible that compilintg the whole distro -Os might be a 
> win? (Intuitively, it seems that everything being a little smaller could 
> have a cummulative effect on the speed of the whole system, saving disk 
> reads, main memory, cache memory, etc.)
> 
> I'm no expert at this stuff, so I figured asking on the list before I do 
> much work would be a good idea.  Searches of the archives don't seem to 
> turn up much except that "-Os can sometimes help".
> 
> So far, I've just played around a little bit with bzip2.  -Os seems to 
> be a pretty good win for bzip2 compression, giving over about a 12% 
> improvement.
> 
> Thank you for any input.
> 
> -Steve Bergman
> 

None of the stuff I know of hasn't looked at x86_64.
You might look at the Code-Size Benchmark Environment (CSiBE):

http://www.inf.u-szeged.hu/csibe/

However, they do not seem to be running the tests for x86_64 at this time.


During the fall of 2004 a couple of students at North Carolina State 
University did some experiments compiling mozilla and the related 
libraries with -Os on x86 machines to see the effect. They found that 
there was some reduction in size and startup time.

http://people.redhat.com/wcohen/ncsu2004/Space Optimizations.pdf


-Will