Re: [PerfSuite-users] CPU time greater than Wall clock time

[Rick K. <rk...@nc...>]

Naveen,

Thanks for sending the document.  We (of course) get the same results 
from post-processing it here as you do, but cannot easily reproduce this 
behavior with our own executables/tests on systems we have available.

There are two suggestions I can think of to try offhand:

1. Add the "time" command to your run, i.e. "time psrun a.out", to get a 
3rd-party opinion of the wall clock and CPU time

2. PerfSuite supports using the "gettimeofday" system call for 
wall-clock timing (by default, on a machine like yours, it uses the 
"rdtsc" asm instruction).  To use gettimeofday, one has to reconfigure 
PerfSuits with the option "--enable-rtc=gettimeofday". Then make clean 
and remake as normal.

If you come across any more info looking into this, we are of course 
very interested to address.  Thanks for reporting.

Rick

Naveen Parihar wrote:
> RIck,
>
> The XML document is attached with this email. I'm trying to debug the 
> problem by directly using high-level PAPI interface. Will let you know 
> my findings later.
>
> -Naveen
>
> On Mon, Jan 5, 2009 at 2:00 PM, Rick Kufrin <rk...@nc... 
> <mailto:rk...@nc...>> wrote:
>
>     Naveen,
>
>     That certainly does sound like a bug, or at least unexpected
>     behavior...
>
>     Would you please send a copy of the XML document that you used to
>     obtain this output?  It may help to look at its contents closer to
>     track down what is going on.
>
>     Rick
>
>     Naveen Parihar wrote:
>
>         Dear Perfsuite users,
>
>         I'm a new user of Persuite/PAPI and would appreciate comments
>         on my query below.
>
>         On a quad core intel runing Fedora Core 6 (kernel 2.6.18), I
>         get the following numbers while runing a *single* threaded
>         program:
>         CPU time (seconds)          47.966
>         Wall clock time (seconds) 30.582
>
>         Since the CPU time > Wall clock time, one conclusion might me
>         a bug in Perfsuite/PAPI or somewhere else.  I double checked
>         the CPU
>         time by dividing PAPI_TOT_CYC count by CPU frequency, and I
>         arrive at the same number. Any ideas on what might be going on
>         or what might be the best approach to debugging this problem
>         is appreciated.
>
>         Thanks,
>         -Naveen
>         ------------------------------------------------------------------------
>
>         ------------------------------------------------------------------------------
>          ------------------------------------------------------------------------
>
>         _______________________________________________
>         PerfSuite-users mailing list
>         Per...@li...
>         <mailto:Per...@li...>
>         https://lists.sourceforge.net/lists/listinfo/perfsuite-users
>          
>
>
>