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From: Steven Cole <scole@lanl.gov>
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Date: Tue, 12 Dec 2000 07:49:48 -0700
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Subject: Re: UP 2.2.18 makes kernels 3% faster than UP 2.4.0-test12
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Helge Hafting wrote:
>Steven Cole wrote:
>[...]
>>Simple question here, and risking displaying great ignorance:
>>Does it make sense to use make -jN where N is much greater than the
>>number of CPUs?
>
>No, but it makes sense to have N at least one more than the number of
>cpus,
>if you have the memory.  This because your processes occationally
>will wait for disk io, and this time may then be utilized to
>run the "extra" task.  But don't overdo it, as you get less disk
>cache this way.  make -j3 seems to be fastest on my 2-cpu machine
>with 128M ram.

Thanks for the answer.  That makes a lot of sense.  When I get the time,
I'll verify that, at least for this fairly narrowly defined task of building 
a kernel.  

In order to minimize external and variable influences on the CPU load, I 
performed all these tests in console mode not connected to a network.  That 
may have been an unrealistic test, as that is not how I normally do kernel 
builds.  Having to juggle more work, like running X and KDE, could shift the 
results (2.2.18 vs 2.4.0-test12) around a bit.  I'll repeat the tests with a 
more normal work environment. If anything statistically significant is found, 
I'll mention it.  Thanks to all for their input.

Steven
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