Parallelism in the build

[Manuel M T Chakravarty]

Just a random data point for those interested: building ghc with make - 
j9 on an 8-core (2x QuadCore Xeon 3GHz) server with the new build  
system requires

   Wall clock:  7m23s
   Work      : 23m11s (16m25s user + 6m46s system)

for a performance build without documentation, without split-objects,  
and without profiling libraries.  (The OS was Mac OS X.  The box an  
Xserve, 2008 model.)

That's a speedup of more than 3 over a sequential build.  That's quite  
good given that there quite a few purely sequential parts in the build  
process.

Manuel

PS: For anybody who believes they should be able to get a speedup  
anywhere close to 8, I recommend <http://www.youtube.com/watch?v=KfgWmQpzD74&feature=channel 
 >