Message-Id: <17015.35256.12650.37887@fisica.ufpr.br>
Date: Tue, 3 May 2005 11:24:56 -0300
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To: linux-kernel@vger.kernel.org
Subject: problem with nice values and cpu consumption in 2.6.11-5
From: carlos@fisica.ufpr.br (Carlos Carvalho)
Sender: linux-kernel-owner@vger.kernel.org
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Look at this cpu usage in a two-processor machine:

  893 user1   39  19  7212 5892  492 R 99.7  1.1   3694:29 mi41
 1118 user2   25   0  155m  61m  624 R 50.0 12.3 857:54.18 b170-se.x
 1186 user3   25   0  155m  62m  640 R 50.2 12.3 103:25.22 b170-se.x

The job with nice 19 seems to be using 100% of cpu time while the
other two nice 0 jobs share a single processor with 50% only. This is
persistent, not a transient. I did a kill -STOP to the nice 19 job and
a kill -CONT, and for a while it decreased the cpu usage but later
returned to the above.

This is with kernel 2.6.11-5 and top 3.2.5. What's the reason for this
(apparent??) mis-behavior and how can I correct it? This is important
because the machine is used for number-crunching and users get really
upset when they don't get the expected share of cpu time...
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