// Some really high Load averages

Using Apache Benchmark (ab)

About two months ago I've benchmarked my Apache with ab:

$ ab -n 2000 -c 100 http://host
  • 2000 requests to perform
  • 100 multiple requests to perform at a time
$ w
 17:28:41 up 17:10,  3 users,  load average: 107,34, 71,08, 32,14
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT

The result was a load average of 107.34 – on a Intel Atom Dual Core with HT (Hyper Threading). That was - until there - definitely my record. Although the optimal load of this system is a average of 4, the system was even accessible and able to reply other request (e.g. Cyrus, NFS, DNS, SSH connections).

Using stress

Today I performed on a backup server with a old Intel Celeron Single Core CPU a stress test with stress:

$ stress -i 10000

…but just on sync() to keep the CPU usage down.
On the left you can see the result of such a stress test and below an output of w before the screenshot was taken.

$ w
 17:28:41 up 22 min,  3 users,  load average: 983,11, 869,82, 904,16
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT

While the system reached a load average of over 1000 it was even reachable! So Munin (on another server) was able to connect to the Munin-Node and generate this graph:

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