Date: Mon, 16 Dec 1996 17:28:12 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: "John M. Aldrich" <fighteer AT cs DOT com>
cc: j DOT potman AT student DOT utwente DOT nl, djgpp AT delorie DOT com
Subject: Re: program with profiling info runs slower with DJGPP 2.01
In-Reply-To: <32B0C83E.221@cs.com>
Message-ID: <Pine.SUN.3.91.961216172426.18715F@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On Thu, 12 Dec 1996, John M. Aldrich wrote:

> Profiling ALWAYS makes your program run slower - there's a tremendous
> amount of overhead involved in detecting each and every function call
> and storing the data.  It doesn't matter whether it's on v2.00 or v2.01.

AFAIK, this is plain wrong.  Profiling in DJGPP works by hooking the 
timer interrupt and recording the profilee CS:EIP.  The only overhead 
this incurs is the additional mode switch when the timer ticks, which 
ain't much at 18 tics/sec.  All the other processing (computing the 
function from the EIP) happens off-line, when `gprof' processes the file 
written by the profiled program.