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Re: Some (small) c++ compilation profiling data (oprofile)

On Sun, May 19, 2002 at 08:38:01AM +0100, Neil Booth wrote:

> > /* time count, time %age, mem ref count, mem reg %age */
> > 
> >     141 /* ht_lookup 149193 3.769% 27240 2.39% */
> I looked on the oprofile site but couldn't see this format of
> output, nor an explanation of what it meant.

Well I added the comment above, I suppose I wasn't clear enough. The
first two numbers are the count and percentage of time spent , the
second two are for the number/percentage of memory references. They are
both statistical not exact.

So roughly 3.77% of execution time was spent in ht_lookup(),
and it caused roughly 2.4% of memory references

> >     163   /* 37996 0.9599% 9582 0.8409% */
> >     164   for (;;)
> I don't understand this either - how can a for statement
> be expensive?  Looking at the numbers shows this is not
> a total for the loop, but is in addition to everything else.

Like I briefly said, it's subject to some inherent unreliable ness. In
fact this number probably represents that this time was spent at the
/end/ of this for loop: by the time the profiler could enquire into the
EIP, it had reached the start of the loop again (due to interrupt
delivery latency). See the example here :

Hope that clarifies things.

"It is very difficult to prophesy, especially when it pertains to the
 	- Patrick Kurzawe

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