Performance analysis for DOS apps?

On 1 Sep 2009 at 11:49, Frej Drejhammar wrote: I'm going to put my foot into it this time... Using time-in and time-out counters may be fine for code where the "hot spots" are known, but in a large complex application, that's almost never the case. P-counter sampling (using a periodic interrupt to obtain the value of the P counter and construct a histogram) can point the problem areas up. But in all of my own experience, the bit-twiddling sort of optimization almost never yields results of the hoped-for magnitude. For example, unrolling loops or scheduling instructions is fine for compilers with automatic optimizers, but not for the programmer who is going to hand-optimize. And the timing differences across an entire family of CPUs often makes this counterproductive. (I can probably still write out the scheduling for CDC 6600 instructions What matters most is the algorithm used. Converting 6 digit binary numbers to decimal by repeatedly subtracting 10 is never going to be faster, no matter how carefully optimized than using, say, the Chinese remainder method. Of course, thinking about one's methods is a lot harder than moving instuctions around and potentially more disruptive. For whatever it's worth, Chuck