Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!snorkelwacker!mit-eddie!uw-beaver!ubc-cs!jalbert
From: jalbert@cs.ubc.ca (Francois Jalbert)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Program Execution Probe
Summary: A simple solution
Message-ID: <5954@ubc-cs.UUCP>
Date: 12 Dec 89 10:22:55 GMT
Sender: news@cs.ubc.ca
Reply-To: jalbert@cs.ubc.ca (Francois Jalbert)
Organization: UBC Department of Computer Science, Vancouver, B.C., Canada
Lines: 29

Earlier today, I mentioned I was looking for a way of determining how much time 
is spent doing disk operations in a typical run of PC-TeX. I got a few replies 
and I would like first, to thank everybody who took the time to reply. The 
easiest solution relies on running your application twice, once in slow 
mode, and then in turbo mode. Assuming the time spent doing disk operations is 
independent of the clock speed, one can deduce the desired information as 
follows. Let 

        D be unknown time spent doing disk-bound operations
        C be unknown time spend doing CPU-bound operations in slow mode
     2C/3 be unknown time spend doing CPU-bound operations in turbo mode
        S be known total time in slow mode
        T be known total time in turbo mode

Then the percentage of time spent doing disk operations in turbo mode is:

       % = 1 - (2/3) (S/T)

I ran a small PC-TeX job and got S=14 secs and T=12 secs. I deduce %=.67
I ran a medium PC-TeX job and got S=42 secs and T=32 secs. I deduce %=.37

I can therefore expect small PC-TeX jobs to go 300% faster with a RAM disk.
And medium ones go only 50% faster. This is all approximate, but gives one an 
idea of what is to be expected.

I am currently reevaluating my need for a 4 Mb RAM-disk.

                                                   Francois
                                                       '