On Saturday, December 7, 2002, at 05:52 AM, Jeremy Erwin wrote:
Ok - I found the message:On Friday, December 6, 2002, at 09:36 PM, Chris Leishman wrote:from unix-porting: (and though I'm actually quoted in the old post, I have little interest in rehashing a potential flamewar).On Saturday, December 7, 2002, at 03:55 AM, Ben Hines wrote:According to Jim Magee (i believe) on the apple list, in his experience -j2 (I think he actually suggested -j3) helps even on single processor systems.I'd be interested in seeing the reasoning there - because it's certainly not what I have experienced in the past (on other platforms) or now (nor can I see how it can be the case). Which apple list are you referring to - I'll go search the archives.
http://lists.apple.com/archives/unix-porting/2002/May/16/ parallelmake.001.txt
According to Jim Magee, he thinks -j[NCPUS+1] can be used to keep both CPU and IO pretty much saturated. I can actually extrapolate on the reasoning for anyone who doesn't fully understand:
Basically, a compile operation will alternate between IO and CPU usage, with the majority being CPU. However, when it is performing IO then the CPU will be underutilized. By running an extra make process, this period of CPU under-utilization by the first compile operation is used up by the second. The assumption is that the IO operations don't overlap (since IO doesn't scale well), but this is a reasonable assumption.
However, this is all working on the assumption that totally saturating the CPU is desired behavior. This is true on dedicated build machines, but I would strongly suggest that it's NOT the case for the majority of fink users. The small gain obtained by saturating the CPU with multiple makes is outweighed by the unresponsiveness of the system in general. Most users are not going to be willing to close every other application and leave their machine alone while it compiles for periods of up to several hours (qt3, kde, etc).
I personally would not want parallel makes running when I use fink. My main system is a 400Mhz TiBook, and I really like to keep doing other things while fink packages build in the background.
If developers really think that parallel compiling would be useful for them, then there should be an option in fink to control it's usage.
Regards,
Chris
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