[Cialug] user vs. sys cpu time

[Morris Dovey]

Kendall Bailey wrote:
| I have a math optimization app that runs for several minutes on a
| dual proc/dual core opteron SLES 9 box.  Plenty of RAM.  It uses 4
| threads to do some parallel computation to take advantage of all 4
| cpu cores. Looking at 'top', or using 'time' to measure cpu time,
| it's logging 30% or more sys time vs. 60-70% user time during the
| parallel phases. I ran it with 'strace -c' and that says only 0.003
| seconds are spent in system calls.  No system calls going on at all
| on the 4 threads. So what does the 'sys' time represent as reported
| by top?

Just a WAG - but servicing timers, checking queues, network I/F, etc.
will eat some system time. Also - top itself is almost likely making
system calls.


Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/