Messages in this thread | | | From | Keith Owens <> | Subject | Re: md mirror / ext3 / dual core performance strange phenomenon? | Date | Mon, 14 Aug 2006 23:22:02 +1000 |
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Erik Slagter (on Mon, 14 Aug 2006 15:12:14 +0200) wrote: >Now, what puzzles me, is that compiling the kernel (2.6.17.7) using >either "make -j1 ..." or "make -j2 ..." or "make -j3 ..." makes the >building take about 6.5 minutes, which is really dissatisfying for this >cpu/harddisks combination. Also, top shows that most of the time both >core are between 10-40% idle. > >BUT... starting from -j4 (and upwards) the compile time suddenly goes to >3.5 minutes!
Nothing to do with the disks, it is a design flaw in the kernel build system. If you want a useful parallel make using -j<n>, set <n> to 3, 4 or 5 higher than the real number of parallel jobs that you want. The exact value to add depends on which kernel tree you are building. See http://marc.theaimsgroup.com/?l=linux-kernel&m=115553906404695&w=2
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