[Cialug] user vs. sys cpu time

[Jerry Heiselman]

On 6/21/07, Kendall Bailey <krbailey at gmail.com> 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?
>
> Thanks.
> Kendall
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I'm not very knowledgable in this area, but perhaps some of the libraries
you are using have to make syscall's to complete.  Perhaps something to do
with the threading.

Like I said, it's just a guess.

-- 
Jerry H
jweida [-at-] gmail [-dot-] com
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