[ale] Recursive make considered harmful

[Joe Morris]

This is from last year but it was new to me.  I wonder how this
would affect the build time for the Linux kernel??

http://www.tip.net.au/~millerp/rmch/recu-make-cons-harm.html

Here's the abstract:

     For large UNIX projects, the traditional method of building the
     project is to use recursive make. On some projects, this results
     in build times which are unacceptably large, when all you want to
     do is change one file. In examining the source of the overly long
     build times, it became evident that a number of apparently
     unrelated problems combine to produce the delay, but on analysis
     all have the same root cause.

     This paper explores an number of problems regarding the use of
     recursive make, and shows that they are all symptoms of the same
     problem. Symptoms that the UNIX community have long accepted as a
     fact of life, but which need not be endured any longer. These
     problems include recursive makes which take ``forever'' to work
     out that they need to do nothing, recursive makes which do too
     much, or too little, recursive makes which are overly sensitive to
     changes in the source code and require constant Makefile
     intervention to keep them working.

     The resolution of these problems can be found by looking at what
     make does, from first principles, and then analyzing the effects
     of introducing recursive make to this activity. The analysis shows
     that the problem stems from the artificial partitioning of the
     build into separate subsets. This, in turn, leads to the symptoms
     described. To avoid the symptoms, it is only necessary to avoid
     the separation; to use a single Makefile for the whole project.

     This conclusion runs counter to much accumulated folk wisdom in
     building large projects on UNIX. Some of the main objections
     raised by this folk wisdom are examined and shown to be unfounded.
     The results of actual use are far more encouraging, with routine
     development performance improvements significantly faster than
     intuition may indicate. The use of a single project Makefile is
     not as difficult to put into practice as it may first appear.


-- 
  Joe Morris, SysAdmin and Not Insane
  "Honey, they're in *everybody's* eggs"  --firesigns