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Re: Need help with CPU shortage [message #36419 is a reply to message #36418] |
Wed, 17 June 2009 13:57 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
maratrus
Messages: 1495 Registered: August 2007 Location: Moscow
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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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Re: Need help with CPU shortage [message #36420 is a reply to message #36414] |
Wed, 17 June 2009 15:02 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
dvazart
Messages: 37 Registered: October 2008 Location: France
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Member |
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Thanks for the explanation.
Finally, noting the times at which the CPU is saturated, I find a crontab from ISPConfig (check_services.php) we have about 100 VEs with ISPconfig installed, so every 30 minutes the CPU reaches the 100% and all the ISPconfig crontabs are running... (now i have to find how to edit the crontab with a shell script in debian).
But your explanation about CPULIMITs its very interesting... so you think we can have 200 VEs running in the same server without CPULIMITS ? We want to have 4 diferents plans of VPS with diferent resources, in our case do you think its possible without CPULIMITS ? and what about the number of CPUS for each VE?
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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?
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So in this case its probably that the script (check_services.php) causes the iowait that we can see in the second image ?
( http://picasaweb.google.com/lh/photo/jUNQXmiO0x7JMkxJSLUv6w? feat=directlink)
thaks..
----------- Daniel Vazart ------------
"Knowledge is power, Sharing is human"
------- http://www.vazart.net --------
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Re: Need help with CPU shortage [message #36427 is a reply to message #36414] |
Thu, 18 June 2009 08:43 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
dvazart
Messages: 37 Registered: October 2008 Location: France
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Member |
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OK....
So CPUS override the CPULIMIT variable ? and if i have something like:
Thats mean the 40% of 1 CPU ?
And another question... i have installed vzsplit (but I do not know the version), you think i can trust in it ?
Thanks !
----------- Daniel Vazart ------------
"Knowledge is power, Sharing is human"
------- http://www.vazart.net --------
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Re: Need help with CPU shortage [message #36437 is a reply to message #36414] |
Thu, 18 June 2009 13:33 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) |
dvazart
Messages: 37 Registered: October 2008 Location: France
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Member |
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Hi !
The last questions :
I'm going to make a shell script with "for" to change the parameters of all VEs, there are some command to disable the CPU variable?
Something like :
vzctl set $VE --cpulimit 0 --cpus 0 --save
The manpage of vzctl only shows :
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--cpus num
sets number of CPUs available in the container.
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And, there are some vzctl command to set the VE0CPUUNITS variable? or i have to set it editing the vz.conf file? I guess i have to restart the daemon after edit VE0CPUUNITS ?
----------- Daniel Vazart ------------
"Knowledge is power, Sharing is human"
------- http://www.vazart.net --------
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