Prism User's Guide - CSAIL People - MIT

114 Prism User Guide
1. Which of the two subsystems that Prism measures does the program
use more heavily? For example, if total serial-subsystem time is greater
than total parallel-subsystem time, then reducing the use of the serial
subsystem is likely to provide the greatest performance gains. Reducing
the use of the parallel subsystem may improve performance, but you may
also find that it will have no effect on performance, since the use takes
place at the same time that the serial subsystem is also in operation.
2. Which resource within this subsystem has the highest usage? If your
program uses the parallel subsystem more heavily than the serial subsystem,
and Send/Get communication is the most-used parallel-subsystem
resource, then you will obtain the greatest performance gains by reducing
the use of this resource.
3. Which procedure uses this resource most heavily? This tells you
where you will have the biggest payoff when attempting to reduce the
use of the most heavily used resource.
4. Which source lines within this procedure use this resource most
heavily? Finally, goinR to the source-line level isolates the svecific lines
of code that have the greatest effect on performance.
Here is an example of a report from the performance advisor (for a CM-2 or
CM-200). Note that it does not include source-line information, because the mostused
resource is FE cpu (user), for which source-line data is unavailable.
Of the two subsystems that Prism currently measures,
your program makes greater use of the front end.
Within that subsystem, your program makes the greatest
use of the "FE cpu (user)" resource, having kept it busy
71% of the total elapsed time.
Procedure complexarray, called from floatarray, called
from MAIN, makes the greatest use of the "FE cpu (user)"
resource, having kept it busy 69% of the elapsed time.
Note that when you first display data for a program, by default the Performance
Data window displays the most-used resource and the procedure that uses this
resource the most; this helps you analyze your data without having to use the
performance advisor.
Version 1.2, March 1993
Copyright 0 1993 Thinking Machines Corporation
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