system tap profiling

[Josh Stone]

On 01/04/2010 11:39 AM, Ivan Novick wrote:
> Hello,
> 
> I am comparing a number of tools for performance profiling including
> system tap, oprofile, and gperf.
> 
> Both oprofile and gperf can determine how much time is spent in the
> functions of a running program, however, they are fooled when a
> process is waiting on IO because the process will not be running in
> the CPU when the tool samples the current state of the process.
> 
> What I have seen from systemtap, it can profile user function calls
> from entry and exit and record a timestamp.  Essentially it can
> measure wall clock time for all user functions in an application,
> regardless of whether they are in CPU or doing IO.
> 
> Am I correct on this, or would there be some reason that system tap
> can not produce a report showing all user functions and the amount of
> wall clock time spent in each function?

Hi Ivan,

Yes, you can create such a report -- just be careful about what the
numbers mean to you.  Wall clock time is not really "spent" in each
function at all -- that time might include many other system activities.


Josh