Hello,
This is the correct behaviour of "time", not a problem. You can
see such results even on dual-core CPUs or on CPUs with multithreading.
I suppose both of the cores are exactly the same make anyway. ;) If you
have a 2-cpu system and run an ideal parallel CPU-intensive workload
under "time", you should get the result system + user = 2*elapsed
Regards,
Daniel
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of [email protected]
Sent: Monday, August 10, 2009 6:06 PM
To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list
Subject: Re: [rhelv5-list] elapsed time - user time - kernel time < 0 ?
Hi everyone,
This problem rang a bell in my mind (back from 1999).
If you are using an SMP system, are the cpu *identical*? I mean, are
they the same make -exactly- (model, clock -and- stepping).
The very same kind of issue happened to me in 1999 when I used a
quad-cpu PPro system as my desktop machine. Because not all these
Pentium-Pro 200Mhz were made with the same steppings (I had three SL22Z
cpus and one
SL048 cpu), the clock would jump back and forth randomly, causing the
PS2 mouse to have occasionnal hicups..
I used the attached C program to display the time deltas (You might want
to run it on your SMP system).
When I got the last non-SL22Z replaced, the time-jump behaviour went
away... I'd check your /proc/cpuinfo for processor differences.. Xig was
very helpful at the time to investiguate the problem but I don't have
the source to their 'timetest' binary (a libc5 binary, I think) to send
you..
If your cpus are identical, then I don't know.. :(
I hope this helps,
Vincent
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