Worrying top output ?

James James at reftech.co.uk
Fri Apr 30 11:46:29 BST 2004


Dave Tiger wrote:

> Just going my dmesg stuff and did a top on my MySql server and this is the
> first line
> 
>   PID USERNAME PRI NICE  SIZE    RES STATE    TIME   WCPU    CPU COMMAND
>   142 mysql     60   0 15528K 12940K RUN    3715.7 98.34% 98.34% mysqld
> 
> The high WCPU and CPU bit worries me as I don’t know what it means but the
> numbers are high.
> 
> The servers performance is blisteringly fast so it dose not seem to be
> affecting it so is it something to worry about or do you clever people know
> what it means and how to rectify it if possible ?

Yeah, it means that someone/you is hitting mysqld with lots of 
concurrent requests; sleeping loops containing queries is the best way 
of handling it, but mysqld 'ramps up' and 'ramps down' CPU usage as it goes.

Check your 'slow queries' output from mysql to see if someone's pushing 
something really heavy through; bad column optimisations or naive 
searches can push usage through the roof on occasions.

James




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