[Nottingham] Gentoo fun on an old VIA Epia C3

[Martin]

Roger Light wrote:
> On Mon, Apr 20, 2009 at 10:43:16PM +0100, Martin wrote:
> 
>>  > At 533MHz on a "VIA C3 Samuel 2", the compile is going to take a
>>  > little while...
[---]
> It works well as my router, file server (nfs/samba), asterisk
> server, apache server, as my persistent client for irc and some
> other bits and bobs. 

I'll be doing similarly.

With no HDD nor CD/DVDROM it runs silently. Rather sweet.

I'd like to put in a couple of 512MByte PC133 DIMMs so that I can run a 
ram disk for /var and further save wearing the flash memory sticks... 
(Scavenged 2x 256MByte for the time being.)


>> Next to try is to see whether the compiler option "Os" is better
>> or not than "O2"... Anyone tried a comparison on a C3?
> 
> This page reckons that -Os isn't recommended:
> http://www.gentoo.org/doc/en/gcc-optimization.xml

There's some very good explanation and advice on that page, thanks. I 
wasn't aware of the O3/Os foibles on gcc 4. I've been long on gcc 3...

Regardless, a quickish test with -Os for recompiling gcc and secondly 
gzip and:

The emerge for gcc presets the compile flags to -O2 in most (all?) 
places in any case.

gzip compiled fine with "-Os" and when testing (1MByte and 24MByte 
files, for "-1" and "-9") gave very similar if marginally slower timings 
to "-O2".

Hence, I'm keeping to the "-O2".


Note that there is an old paper somewhere (for gcc 3?) where someone 
recompiled glibc with "-Os" and saw a speedup for their system due to 
reduced code size. I guess it looks like we'll need to wait for further 
gcc 4 development before we might see that effect again...

Always interesting to test!


Cheers,
Martin

-- 
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Martin Lomas
martin at ml1.co.uk
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