suggest 'make -j2' for SMP machines?

Miguel Bazdresch lfs-01 at thewizardstower.org
Mon Jun 4 18:35:48 PDT 2007


Deskin Miller wrote:
> I'm new to the list, having recently built an LFS system on an old
> Pentium Pro machine, and I'm now in the middle of building another on
> an SMP Pentium II box.  I noticed, while timing the SBU compilation of
> binutils in Section 5.3, if I put 'make && make install', that the
> wall-clock time was about 12m56s; while user time was about 7m.  If
> instead I compiled with 'make -j2 && make -j2 install', wall-clock
> time went down to about 8m, with negligible change to user time

My understanding is that you should use make -j X, where X is the 
number of cores on your system. If X is less than the number of 
cores, then you're underutilizing your system; if higher, you're 
overutilizing it and performance will plummet.

As far as mentioning it in the book... I'm not enthusiastic, since 
it's basic knowledge of how your computer works... OTOH we already 
say some pretty basic things, and the proliferation of multicore 
CPUs might warrant a mention of make -j.

-- 
Miguel Bazdresch
http://thewizardstower.org/



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