[Compilation]Very abnormal compilation time.

[Djento]

Hi,

I'm not new to Gentoo's world, but it makes a moment i didn't use it, so now, i've installed the current release of Gentoo and i'm experiencing very bad compile time compared with old experience.
I suspect gcc but why? Is there a signficant changment during these last 7months?

I explain: my previous computer was an petium-m 1.5Ghz with 768mb DDr2, i lost it in April, i'm currently running a pentium-m 1.4Ghz with the same amount/type of memory but the time compile between both are huge.
Look, kernel compile time on my old 1.5Ghz Pentium M was about ~14min, here on the 1.4Ghz Pentum M increases of 30minutes.
Another example: Gimp took me 15-20minutes on my old P-M 1.5Ghz, here on the "100mhz in less" one, it takes more than one hour.

My GCC:
- gcc (GCC) 4.1.1 (Gentoo 4.1.1-r3)
flags: CFLAGS="-O2 -mtune=pentium-m -pipe"

Libs C/C++ are up to date

My harddisk perfs seems correct too:
a 4years old toshiba 40gb 8mb 7200rpm
hdparm -tT /dev/hda:
Timing cached reads: 416 MB in 2.00 seconds = 207.63 MB/sec
Timing buffered disk reads: 74 MB in 3.05 seconds = 24.29 MB/sec

In fact, on the Apple Powerbook G4 1,67 Ghz+1,5Gb DDR2 of my brother, compile time is also too long, in the same range, it is simply abnormal.

What's wrong?

thank you

[NathanZachary]

Well, I have never used -mtune in my /etc/make.conf. I usually use -march=xxx. On my laptop with a Pentium-M, I actually set the -march=pentium4 and saw much better compilation times (with no errors). Possibly you could try that. I have had no negative experiences with gcc-4.1.1.
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[Akkara]

Sometimes a speed difference can be the result of different RAM or timings.

Are the motherboards similar? Bios updated?

There was a old motherboard that kept giving me errors which turned out to be bad settings for the RAM - most were too conservative but one was too aggressive (and the cause of the errors). After some hand-tuning I had managed to fix the errors while also increasing the memory bandwidth 30% or so.

[Djento]

Hi,

Thanks for your responses.
Well, i could try -march=pentium4 ou i686 but it will be very strange.

The motherboard is different but chipset is the same. Harddisk too, memory DDR2 266 same.
oh, my current computer use a shared memory vga card (about 16mb)

I used the same make.conf coming from my good experience, the only difference is on my reference computer i began installation on stage 2 and i compiled myself GCC and . Here, the P-M 1,4Ghz and by the past on the G4 1,67Ghz, i used these provided with the distro 2007.x (x86 and PowerPC respectively)

Indeed, that's very strange, if you need more details (Hardware, Kernel config), just ask.

I'm going to try -march option and recompile my GCC

AkKara: what's the options were changed in your BIOS?

EDIT: I'm suspecting the PREEMPTION MODE currently activated, let's digg it.

Regards

[obrut<-]

can it be, that the 1,5 ghz cpu had 2 mb of cache and your current one only 1 mb? a shared memory graphics card does not just eat up some ram but it also reduces the memory bandwidth. in combination with a smaller cache this can degrade performance. you can speed up compilation times by mounting a tmpfs on /var/tmp/portage. search the forums for "temerge". it's a wrapper script that does the mounting an unmounting for you.

[Djento]

Hi,

No, both Pentium-M banias had 1mb of cache.
Well, preemption was activated in voluntary mode, firstly i've changed to "no preempt", made a compilation and there was no big difference.
Now i recompiled in preemption for desktop, freq latency 1khz, i'm trying to remake a compilation without real expectation anyway.

obrut<- : i'm going to investigate the "temerge" way.

Thank you

[didl]

You didn't happen to have ccache enabled on your old box?

[Akkara]