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Subject: unexpected idprio 31 behavior on 9.2-BETA2 and 9.2-RC1
From: Dave Mischler <dave@mischler.com>
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Date: Mon, 05 Aug 2013 17:15:16 -0400
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I have an i5-2500 machine 8GB RAM now running 9.2-RC1 amd64 with the
GENERIC kernel. Today, while still running 9.2-BETA2, I updated my
source tree and started building world with idprio 31 and I looked back
a while later and all the CPU cores and disk were essentially idle, and
hardly any progress had been made on the build. I stopped and restarted
the build without the idle priority setting and it ran fine. Anybody
else seen any of this? Anybody know about any fairly recent changes that
might account for it?

I did a "rm -rf /usr/src /usr/obj" and loaded a new source tree before
going to RC1.  I still see odd behavior at RC1.  Sometimes it works just
like it should (i.e. compute bound processes use most/all of the
available CPU time), but a lot of the time both the CPU and disk are
idle (e.g. CPU 97.8% idle, disk 1% busy per systat).  I don't think I
ever saw this behavior before while running "make buildworld -j4".  Can
anyone else confirm/rebut my findings?  Thanks.