Re: if-conversion a performance bottleneck

[Brad Lucier <lucier at math dot purdue dot edu>]

> On Thu, May 04, 2000 at 10:31:59PM -0700, Mike Stump wrote:
> > Unfortunately -j3 gives you not three jobs, but an exponential cascade
> > of 3 jobs per recursive make level.
> 
> I know.  But 3 or 15 is still a lot better than 1000, which might
> be what you get with just -j.
> 
> > I found that -j3 -l10 will at least try and limit them from expanding
> > too much, which is useful if your swap limited (just how did those 2
> > emacen grow to be 60M each, and netscape inflate to 90M? :-().
> 
> That's what gigabytes of RAM are for.  ;-)

I have gigabytes of RAM; I've watched what happens when I say, e.g.,

make -j9 bootstrap

or

make -j 9 bootstrap

or whatever, and it doesn't seem to actually set off a bunch of parallel
jobs---definitely, by the time the stage1 compiler starts compiling
things, I'm down to one job at a time.  That's with the 2.2.13 kernel
on alpha with make 3.77; is this a known problem?  Should I upgrade
make?

BTW, the maximum load with make -j is < 80 (without libgcc) and
things seem to stay rational because make gets less time as the
load rises and can't spawn jobs at such a high rate.

Brad