North American Network Operators Group
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Linux routing

  • From: Ralph Doncaster
  • Date: Tue May 21 18:35:51 2002 
I don't really trust the vmstat system time numbers.  Based on some
suggestions I received, I ran some CPU intensive benchmarks during
different traffic loads, and determined how much system time was being
used by comparing the real and user times.  The results seem to show that
if I want to do 50Mbps full-duplex on 2 ports (200M aggregate) that the
standard Linux 2.2.20 routing code won't cut it.

Unloaded Duron 1G
[email protected] ~# time bzip2 /tmp/words 

real    0m0.414s
user    0m0.400s
sys     0m0.010s

750Mhz Duron, ~20Mbps traffic, 8K int/sec
vmstat reported CPU idle: 98% (2% system)
[email protected] ~# time bzip2 /tmp/words 
real    0m0.628s
user    0m0.380s
sys     0m0.160s
CPU load ~= 40%
[email protected] ~# time bzip2 /tmp/words 
real    0m0.552s
user    0m0.460s
sys     0m0.090s
CPU load ~=16%

750Mhz Duron, ~60Mbps traffic, 20K int/sec
vmstat reported CPU idle: 95% (5% system)
[email protected] ~# time bzip2 /tmp/words 
real    0m1.071s
user    0m0.370s
sys     0m0.690s
CPU load ~= 65%
[email protected] ~# time bzip2 /tmp/words 
real    0m1.041s
user    0m0.440s
sys     0m0.600s
CPU load ~= 58%