To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: gprof problems
Date: Thu, 25 Aug 94 18:20:51 +0300
From: eliz AT is DOT elta DOT co DOT il

A few problems I had recently working with gprof:

1. It seems that profiling doesn't work under DPMI, except counting
the number of times each function was called.  mcount_isr_init()
(on crt0.s) explicitly tests for run_mode to be not more than 3,
while DPMI is 4 (see include/go32.h).  Is there some inherent
incompatibility between DPMI and the timer tick interrupt, or
is this just a bug?

2. Also, I would suggest to reprogram the timer to work with finer
granularity than the default 55 msec.  This would add only a few
more machine instructions to the interrupt handler (to pass the
interrupt down the chain only every n interrupts, so the system
time runs at normal speed), but will greatly enhance the accuracy
of the profile.  55 msec is really too coarse for most functions,
and would skew the profile for programs which take a short time
to execute.  Another possibility is to use the CMOS clock which
ticks every 1 msec, and can generate an interrupt if you ask nicely
enough.  This has an advantage of not messing up with the system
timer.

3. It seems to me that the time spent outside the protected-mode code
(including the library), e.g., when go32 does something on behalf
of the user, doesn't get counted.  For instance, a program which
does lots of I/O doesn't get the time spent in I/O routines below
the library listed.  Is this really so?  If it is, where is it
implemented?  I saw the skip_mcount flag in the timer handler,
but didn't find anybody but mcount() itself setting that flag.  Does
go32 somehow sets it also?  If so, where?  And is this intentional?
This might make sense under Unix environment, but for single-task
DOS it effectively makes a very biased picture of where the does the
program spend most of its time.

4. I also have noticed that some functions don't have a count
of the number of times they were called listed in the profile.
Two examples are findfirst and findnext.  Why is that?

	Eli Zaretskii