kern/126880: CPU usages are unbalanced

[Kris Kennaway]

The following reply was made to PR kern/126880; it has been noted by GNATS.

From: Kris Kennaway <kris at FreeBSD.org>
To: KOIE Hidetaka <koie at suri.co.jp>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: kern/126880: CPU usages are unbalanced
Date: Wed, 27 Aug 2008 16:14:15 +0200

 KOIE Hidetaka wrote:
 > Idle times per CPU can be watched by top(1).
 > But these times are clearly different.
 > 
 >> How-To-Repeat:
 > This machine is dual-core opteron and dual-socket.
 > koie at guriandgura% top -HSn|grep idle
 >    11 root       171 ki31     0K    64K RUN    0  26.7H 41.55% {idle: cpu0}
 >    11 root       171 ki31     0K    64K RUN    2  23.5H 31.88% {idle: cpu2}
 >    11 root       171 ki31     0K    64K RUN    1  19.9H 15.19% {idle: cpu1}
 >    11 root       171 ki31     0K    64K RUN    3  20.8H  9.18% {idle: cpu3}
 
 Do you have evidence that this is causing a performance problem?  Your 
 system is not 100% busy anyway, and it is often better to keep a 
 long-running task running on the same CPU where it can benefit from hot 
 caches rather than bouncing it around between CPUs where it will suffer 
 from lots of cache misses.
 
 Kris