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Date: Sun, 24-Nov-85 21:58:11 EST
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Posted: Sun Nov 24 21:58:11 1985
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Subject: Program Counter Profiling on VMS

[Forgive me, I missed the orignal posting - our news feeds were down for
 about a week - ta2                                                      ]

I have a program counter sampler for VMS. You link it into the program to
be tested as a user written debugger. (LINK/DEBUG=PCSAM ....) By default,
sampling is not enabled. If you set the logical name $PCSAM$ to anything
less than 5 characters, sampling will be enabled on a 50ms timer AST. If the
equiv name for $PCSAM$ is longer than 5 characters, the sampler will use
it as a delta time string and sample at that rate. PC's are collected into
a file whose name is derived from the image name; ie IMAGE.EXE --> IMAGE.PCS.

If a PC occurs twice in a row, and the instruction at that PC is a
CHMK or CHME, the redundant PC will be discarded. This eliminates the
data getting swamped by long waits at system service calls (like terminal i/o).

After the PC's are collected, the .PCS file and the .EXE file are fed into
the report generator. The report generator reads the traceback information
from the .EXE to determine the start and end points for all routines. It
then assigns each PC from the .PCS to each routine producing a histogram
when done.

The report generator allows setting of a display threshold. All routines
that accumulate less percent PC's than the threshold will not be displayed
in the histogram.

I ran some quick tests under VMS 4.2, it seems to still work!

If anybody would like this package, contact me through mail or on
the Bellophone. I'll mail the sources out to those requesting them.
The sampler is written in assembler, the report generator in Pascal.

Tom

...............
tom allebrandi 2, general electric automation controls operation
UUCP: ...ucbvax!decvax!mcnc!ncsu!uvacs!edison!ta2
  or  ...seismo!cbosgd!uvacs!edison!ta2
box 8106, charlottesville, va, 22906      (804) 978-5566
...............