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  1. #1
    Join Date
    Sep 2000
    Posts
    497

    CPU usage unusually high

    Hello,

    I need the assistance of some experts here.

    I have a server that is using unusually high CPU percentage for simple tasks.

    When there is a http request, it can go as high as 22%

    Doing a qscan goes as high as 97%

    This is a P4 2.8. 1 gig ram, IT is hard to believe that a simple http request uses that high percentage of memory. Or qmail scans are shutting down the server.

    I have another server that is a p4 2.4 and http requests use less than 1 % which makes sense to me.

    Any ideas of what types of setting I could have that causes this problem?

    Note: Very little traffic on the server. Very few users.

    thanks

    David
    Systematic Software
    [email protected]
    http://www.systware.com

  2. #2
    Join Date
    Jan 2002
    Location
    Home, chair
    Posts
    723
    You should look at the load average values probably first, if they are ok, then there's nothing to worry about. Can you post a 'top' output here?

  3. #3
    Join Date
    May 2003
    Location
    Virginia
    Posts
    298

    Re: CPU usage unusually high

    Originally posted by diyoha
    Hello,

    I need the assistance of some experts here.

    I have a server that is using unusually high CPU percentage for simple tasks.

    When there is a http request, it can go as high as 22%

    Doing a qscan goes as high as 97%

    This is a P4 2.8. 1 gig ram, IT is hard to believe that a simple http request uses that high percentage of memory. Or qmail scans are shutting down the server.

    I have another server that is a p4 2.4 and http requests use less than 1 % which makes sense to me.

    Any ideas of what types of setting I could have that causes this problem?

    Note: Very little traffic on the server. Very few users.

    thanks

    David

    Are you talking about transient high utilizations or sustained? On one of my servers - Dual 2.4 Xeon with 3G RAM I frequently see processes like httpd, exim, qmail etc) grab 99% of the processor for brief periods of time. There is nothing wrong with that as long as it stays brief.

    You may want to study up a bit more on how linux allocates cpu time.

    TP

  4. #4
    Join Date
    Sep 2000
    Posts
    497
    Here is an example top output

    19:56:52 up 10 days, 5:23, 1 user, load average: 0.17, 0.08, 0.02
    135 processes: 132 sleeping, 3 running, 0 zombie, 0 stopped
    CPU states: cpu user nice system irq softirq iowait idle
    total 54.5% 0.0% 21.2% 0.0% 3.0% 0.0% 21.2%
    Mem: 1014396k av, 989860k used, 24536k free, 0k shrd, 384832k buff
    752056k actv, 189080k in_d, 5236k in_c
    Swap: 1052248k av, 175732k used, 876516k free 374008k cached

    PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
    4748 qscand 23 0 5552 5552 1924 S 39.5 0.5 0:00 0 perl5.8.0
    4752 qscand 25 0 916 916 736 R 27.3 0.0 0:00 0 clamscan
    4665 diyoha 15 0 1300 1300 900 R 6.0 0.1 0:02 0 top
    1 root 15 0 492 464 436 S 0.0 0.0 0:03 0 init
    2 root 15 0 0 0 0 SW 0.0 0.0 0:33 0 keventd
    3 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 kapmd
    4 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
    Systematic Software
    [email protected]
    http://www.systware.com

  5. #5
    Join Date
    Sep 2000
    Posts
    497
    Are you talking about transient high utilizations or sustained? On one of my servers - Dual 2.4 Xeon with 3G RAM I frequently see processes like httpd, exim, qmail etc) grab 99% of the processor for brief periods of time. There is nothing wrong with that as long as it stays brief.

    You may want to study up a bit more on how linux allocates cpu time.
    Well that seems like what is happening. The reason it drew a red flag from me is I have the other identical server which does not do that.

    The other thing is my monitoring software is checking to check the load, and I keep getting notifications. The only thing I could see was the CPU sometimes went as high as 99%, the load always looked okay.

    thanks

    David
    Systematic Software
    [email protected]
    http://www.systware.com

  6. #6
    Join Date
    May 2003
    Location
    Virginia
    Posts
    298
    Originally posted by diyoha
    Here is an example top output

    19:56:52 up 10 days, 5:23, 1 user, load average: 0.17, 0.08, 0.02
    ksoftirqd/0

    Those load averages look good. Another tool to use is 'vmstat' and 'iostat'. Also you should check and see if sar is installed.

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