[IPython-user] What is System time in timing report?

[Dick Moores]

Thanks very much!

Dick

At 02:04 AM 8/17/2008, Fernando Perez wrote:
>Hi Dick,
>
>sorry for the delayed reply...
>
>On Fri, Jul 25, 2008 at 7:59 AM, Dick Moores <rdm@rcblue.com> wrote:
> > In [12]: run -t -N100 1s.py
> >
> > IPython CPU timings (estimated):
> > Total runs performed: 100
> >   Times :      Total       Per run
> >   User  : 4.08950523041 s, 0.0408950523041 s.
> >   System:        0.0 s,        0.0 s.
> >
> > What is "System"? And what kind of things in a script would raise
> > System time above zero?
>
>On a Unix OS, the kernel distiguishes between time spent by your
>program making system calls and time running your own code.  So for
>example if your script makes lots of large memory allocations, you may
>see sufficient system time reported.  Windows doesn't report system
>time separately, so under windows this is always zero.  IPython gets
>this information via the getrusage call:
>
>
>
>
>NAME
>        getrusage - get resource usage
>
>SYNOPSIS
>        #include <sys/time.h>
>        #include <sys/resource.h>
>
>        int getrusage(int who, struct rusage *usage);
>
>DESCRIPTION
>        getrusage()  returns  current  resource  usages,  for  a 
> who  of  either
>        RUSAGE_SELF or RUSAGE_CHILDREN.  The former asks 
> for  resources  used  by
>        the  calling process, the latter for resources used by those 
> of its chil-
>        dren that have terminated and have been waited for.
>
>            struct rusage {
>                struct timeval ru_utime; /* user time used */
>                struct timeval ru_stime; /* system time used */
>                long   ru_maxrss;        /* maximum resident set size */
>                long   ru_ixrss;         /* integral shared memory size */
>                long   ru_idrss;         /* integral unshared data size */
>                long   ru_isrss;         /* integral unshared stack size */
>                long   ru_minflt;        /* page reclaims */
>                long   ru_majflt;        /* page faults */
>                long   ru_nswap;         /* swaps */
>                long   ru_inblock;       /* block input operations */
>                long   ru_oublock;       /* block output operations */
>                long   ru_msgsnd;        /* messages sent */
>                long   ru_msgrcv;        /* messages received */
>                long   ru_nsignals;      /* signals received */
>                long   ru_nvcsw;         /* voluntary context switches */
>                long   ru_nivcsw;        /* involuntary context switches */
>            };
>
>
>Cheers,
>
>f