Date: Thu, 14 Oct 2010 15:46:13 -0400 From: Martin Turgeon <freebsd@optiksecurite.com> To: freebsd-questions@freebsd.org Subject: How is CPU usage calculated? Message-ID: <4CB75E05.4070207@optiksecurite.com>
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Hi list! I did a strange observation yesterday night. The CPU usage reported by top doesn't match what is indicated under it. I was seeing around 80-90% user, 5% system, 1% interrupt and 10% idle. But the process details under it doesn't match. mysqld was taking around 250% (WCPU) with a few httpd processes at 1-2%. The system is running GENERIC 8.0-REL on a Xeon E5630 (quad core with hyperthreading so 8 CPUs). MySQL and Apache each have their own jail (I don't think it will matter but just in case) I understand why the mysqld process take more than 100% but how can I know what's taking the rest? Why doesn't the total user CPU usage match the total of the CPU usage of each process? Is there a link with hyperthreading? There sure is a logical answer and I would really like to know it :) Thanks in advance, Martin
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