[CentOS] Load Average

Lamar Owen lowen at pari.edu
Wed Mar 1 21:34:11 UTC 2006

On Wednesday 01 March 2006 13:45, Peter Farrow wrote:
> You need to check out whether the system is waiting on  IO,  on the
> version of top on Centos 4.2 it doesn't show IO wait on the display, but
> on the RH enterprise shipping version it does.

> A load average of 9 is getting high, you expect would services like
> sendmail to stop listening once the system load average gets to 12.

As a data point, on my Sun E6500 during load testing a few months back, under 
Aurora SPARC Linux (I would expect similar performance from CentOS SPARC) I 
was pulling a load average of 250+ with little interactive degradation 
(command line mode).  The E6500 had 14 CPU's and 16GB of RAM at the time, and 
was serving an ab load (apache bench) of 256 concurrent requests to a Koha 
integrated library system backend, over a total of 2.5 million requests.  
Every page hit the database at least twice, from Perl.  System at that load 
average was serving 6 pages per second; at a concurrency of 1, system served 
4 pages per second, so performance increased as load did.  I would have hit 
it with more concurrency, but httpd was compiled with a 256 connection max 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772

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