From owner-freebsd-questions@FreeBSD.ORG  Sat May 23 19:51:08 2009
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Date: Sat, 23 May 2009 12:51:06 -0700
From: Yuri <yuri@rawbw.com>
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Subject: Why build's user CPU on 4-CPU machine with hyper-threading always
 higher with -j 8 compared to with -j 4?
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I noticed that the same exact build on i7-920 (4 CPUs) consumes ~15% 
more user CPU when run with -j 8 compared to -j 4.

Hyper-threading is enabled so top shows 8 CPUs.

Why would user time be higher in a  hyper-threaded run?

Yuri