On Friday, December 6, 2002, at 09:36  PM, Chris Leishman wrote:

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.

from unix-porting: (and though I'm actually quoted in the old post, I have little interest in rehashing a potential flamewar).



From: Jim Magee <[EMAIL PROTECTED]>
Date: Thu May 16, 2002 1:16:51 PM US/Eastern
To: Jeremy Erwin <[EMAIL PROTECTED]>
Cc: [EMAIL PROTECTED]
Subject: Re: parallel make

On Thursday, May 16, 2002, at 12:30 PM, Jeremy Erwin wrote:

The topic of parallel make (i.e make -j) came up on one of my other mailing lists (fink-devel). Someone proposed using make -j2 in certain fink packages to speed up builds on dual processor systems.

Assuming that the make process is not affected by race conditions, would a dual processor system benefit most from "-j2", "-j4", or -"j" (unlimited job spawning)?
I have always found that Darwin builds benefit most from -j(NCPUS+1). That tends to keep both I/O and CPUs saturated pretty evenly. At least that's true with the xnu kernel build, and it seems to match what others have found under other BSDs as well.

The xnu makefiles are set up for parallel builds, but not many other Darwin ones are by default (I have no idea about Fink projects).

Would a uniprocessor system benefit?
Yes. About 20% improvement from what I have seen. But it all depends upon how big the project is and how much CAN be done in parallel.

For the sake of argument, the primary purpose of these computers would be to compile binaries as quickly as possible-- not smoothly running Omniweb, or Mail...

How much would running the computer in ">console" mode help?
I think the console mode would slow you down. Ssh or telnet from another machine is typically the fastest.

--Jim
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