Re: [gentoo-amd64] compiling on dual-cores - only 50% usage per cpu

[Peter Humphrey <prh@gotadsl.co.uk>]

On Saturday 10 Nov 2007, Bernhard Auzinger wrote:

> it's not a important question, but has anybody of you noticed when
> compiling certain packages the load on both cpu's is only about 50%. I
> have the feeling that it happens with packages that can not be split up
> into two jobs. But in this case one cpu should be on 100% load and the
> other one at ~0%. Maybe someone of you has a good explanation for this
> behaviour.

I posted a question like this a few months ago, and I did a fair amount of 
detective work. Pretty much inconclusive, I'm afraid, but it seemed to be 
due to a motherboard chipset problem. This is a SuperMicro H8DCE; the 
problem only appeared when this replaced a faulty MSI board. I think the 
conversation ran in May, so you should be able to find it in the archive if 
you're interested.

(I'd noticed that the BOINC scheduler was trying to get two processes run at 
full load, one on each CPU, but according to /top/ and /gkrellm/ each was 
getting just 50%, sometimes one on each CPU and sometimes both on the same 
one. And /top/ seemed confused about which CPU was running which tasks!)

I don't run BOINC any more, for other reasons, so I haven't run into the 
problem recently. Kernel compilations seem to go OK, so it's all a bit of a 
mystery. I concluded at the time: "I'm left with a vague feeling of 
dissatisfaction from not knowing what's going on, and a suspicion that 
something in the nForce2 chipset doesn't match what the kernel thinks. 
Kernel versions seem not to affect this problem, at least not in the range 
of versions I could find."

-- 
Rgds
Peter.
Linux Counter 5290, Aug 93
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