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From "Bill Bawcombe" <>
Subject [users@httpd] Apache HTTPD Sporadic High CPU
Date Tue, 10 Apr 2012 21:51:44 GMT
We are sporadically experiencing high CPU with our Apache instances.
The CPU averages about 5% utilization normally and has run fine for over
a year without an issue but over the past month we see spikes up to 100%
utilization that never drop until the instance is bounced.  We can go up
to a week before we see the issue but we've also seen it happen multiple
times in a day.  The logs are not indicating any errors for further
investigation and we only have this issue in our Production environment.

Things we've tried:
-We've searched numerous topics on Apache HTTPD and high CPU and with
regards to tuning parameters but considering we haven't had an increase
in usage and our average CPU utilization is normally low we are
reluctant to make tuning changes without understanding what else we may

-We ran prstat and the one anomaly we've seen is the Involuntary Context
Switching (ICX) seems to be high when the CPU spikes.  Normally ICS is
in the single digits but when the CPU spikes we see thousands.  From
observation it appears that the ICX value and CPU utilization increase
and drop simultaneously. 

Information regarding our environment:
- Apache HTTPD 2.2.20 
- MOD_PROXY as a reverse proxy
- Solaris 10
- 2 servers for high availability and have experienced the issue on both

One other note is that we are using CA's SiteMinder (authentication and
authorization) agent for Apache.  We've exhausted all of the support CA
will give us regarding this issue and they have no other known issues
from their customer base.  


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