Summary: Eek! cpu usage 98%

From: Doug Wright <ppstech_at_nbnet.nb.ca>
Date: Fri, 08 Mar 1996 13:41:20 -0400

Thanks to all who replied,
here is the original question plus all the replies I received.

I have recovered...


Hi managers,
when running iostat on our DEC ALPHA 1000 4/200 running OSF/1 our cpu usage
ubder sys is constantly around 98% any ideas on what could be causing this
and how to fix it. We are running a low hit webserver and have never had
numbers like this before. All advice is appreciated!
--------------------
    Doug Wright
ppstech_at_nbnet.nb.ca
-------------------

---------------------------------------------------------------------------

Hi Doug,

Do you have top or syd? These utilities will display your utilization so
you can get a handle on what is happening.

You may even want to try ps augx|more to see who has the highest
percentage of the CPU.

                                 Regards, Dave

--------------------------------------------------------------
- David L. Cairns E-mail: cairns_at_upei.ca -
- Systems Manager Voice: (902) 566 0388 -
- UPEI Computer Services Fax: (902) 566 0958 -
- Charlottetown, PEI CANADA -

---------------------------------------------------------------------------

Regards,

Check the CPU consumers with 'ps' or get 'top' to monitor the CPU intensive
processes.

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---------------------------------------------------------------------------
use:
ps -o pid,ppid,user,ni,vsz,rss,start,cputime,pcpu,comm
to check which process is taking up the CPU time (specifically the pcpu
entry gives this info).
Best regards,
                                            -gjb-
                                   http://www.luc.ac.be/~gjb/
                            PGP public key: finger gjb_at_alpha.luc.ac.be
----------------------------------------------------------------------------
re: cause
A lot of time being spent in kernel mode; network drivers, disk
driver, file systems, etc.
Use ps(1) to see what processes are collecting a lot of CPU
time.  If you can find a copy of top, it should make that
easier.  If you can identify a single process or related
group of processes that are the cause, then you can figure
what that process does that is kernel mode intensive.
You can pick up Monitor from gatekeeper.dec.com:/pub/DEC/monitor.alpha.Z
(a compress tar archive).  It will present much of the information collected
by iostat, vmstat and netstat all at once.  With it you can see what
is going on system wide at the same time.
One type of "I/O" load that causes this type of usage is read
heavy I/O load that is hitting the buffer cache most of the
time.  With out disk I/O little time is spent waiting, and
processes are just moving data around.  Another, rather trivial
example, is a program which just does getpid() repeatedly.
-----------------------------------------------------------------------------
It may be that one of your httpd processes is hung.  Get "top" from
ftp://eecs.nwu.edu/pub/top (latest version is 3.3) and run that - it'll
tell you a lot more about what processes are doing.
Pat Wilson
paw_at_dartmouth.edu
--------------------
    Doug Wright    
ppstech_at_nbnet.nb.ca
-------------------

Received on Fri Mar 08 1996 - 19:59:50 NZDT