| Re: Need help with CPU shortage [message #36419 is a reply to message #36418] |
Wed, 17 June 2009 13:57   |
maratrus
Messages: 1495
Registered: August 2007
Location: Moscow
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Senior Member |
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Hi,
a few words about CPULIMITs.
What purpose do we pursue restricting VEs CPULIMIT? Not allow a particular VE to use a free CPU? So, in case of intensive CPU consumption on the part of VEs, CPUUNITS are the main restriction that balances the system load. In case of low CPU consumption we would be likely restricted by CPULIMITS (if they don't equal to zero) while actually CPU would be idle. Thus, it's not clear what kind of benefit we'll obtain by setting up CPULIMIT parameters. Moreover, the situation may occur when a particular VE holds some kind of locks (and other VEs wait these locks too) but cannot release them because of the CPULIMIT restriction. But it worth saying that in case of CPULIMITS=0 this situation may occur too (hence, with less probability). So, if somebody wants to set up CPULIMIT parameters it's of course not prohibited but it worth bearing in mind the above arguments. May be worth disabling CPULIMITs at all?
The first provided output of htop utility shows rather big load average value. There are either processes that couldn't obtain CPU (e.g. because of the CPULIMIT) or processes in D-state producing a lot of i/o operations. BTW, does htop takes into account processes that are in D-state? Is it worth either tuning it or comparing htop output with 'top' or/and 'ps' outputs?
htop output indicates that "minicom-cron", "php script" and "getty" consume 100% CPU. Is it their permanent behavior? Why do they consume so much CPU?
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