High CPU at every xx:55 (every hour)

thanasis

• January 24, 2018 06:17

Hello, i noticed that every hour and especially at xx:55, my vps server cpu goes at limit for 2 minutes and then goes down... Im using htop command but i didn't see any high cpu or memory process... Any idea ? Here are some screeenshots

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  thanasis

  • January 24, 2018 14:58

  I found the problem! At the /var/log/cron there is a command "sync; echo 3 > /proc/sys/vm/drop_caches" which cause the problem. I see this command every xx:55 Shall this command execute every hour? How can i change the cronjob of this command ?

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  cPanelMichael

  • January 24, 2018 16:04

  Hello, That looks like a custom cron job. If you did not add it, I recommend contacting your VPS hosting provider so they can confirm it's purpose and if they recommend removing it. Thank you.

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  thanasis

  • January 24, 2018 16:14

  Can i change myself ? How can i find this cronjob (at this file) ?

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  cPanelMichael

  • January 24, 2018 16:17

  Hello, Check to see if it exists within a script in the /etc/cron.hourly/ directory. It's not a required command, but you may want to consult with your VPS hosting provider, as they may have added it for a reason. Thank you.

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  thanasis

  • February 03, 2018 15:12

  Hello, they suggest me to chhange the "echo 3 > ..." line to "echo 1 > .." in order to only free the page cache instead of also freeing dentries and inodes. I found this: To free pagecache: echo 1 > /proc/sys/vm/drop_caches To free dentries and inodes: echo 2 > /proc/sys/vm/drop_caches To free pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches Before i removed the "echo 3 > ..." i checked my RAM. It had: 30717040 total, 25244176 free, 2631884 used, 2840980 buff/cache After 5 hours i have (i had removed "echo 3 > ...") : 30717040 total, 21581380 free, 2164572 used, 6989240 buff/cache Am I OK, What do you suggest?

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  thanasis

  • February 03, 2018 21:20

  After a couple of hours.... KiB Mem : 30717040 total, 244400 free, 2790844 used, 27681796 buff/cache What do you think? Shall i have to set again the "echo 3 > ..." or "echo 1 > ..." or im OK with these ?

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  cPanelMichael

  • February 12, 2018 15:36

  Hello, It's difficult to know for sure what the results of the change will be, as it depends on your existing hardware and resource usage. I recommend checking with your provider for more information about their recommended change. Thank you.

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