[CentOS] Load Average

Johnny Hughes mailing-lists at hughesjr.com
Wed Mar 1 22:22:41 UTC 2006


On Wed, 2006-03-01 at 16:34 -0500, Lamar Owen wrote:
> 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.
I generally try to keep max load to no more than 2 - 2.5 times the
number of processors in the machine ... so that is 8-10 for a quad
processor machine ... 4-5 for a dual processor and 2-3 for a single
processor machine.

That assumes that there is actual IO and load on the processes and not a
high load number with lots of idle time.  So, those numbers and ~100%
CPU utilization is what I shoot for as maximums.

I'm sure other people have different goal numbers.

> 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 
> limit.


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