Makefile profiling

Question

So I have this Makefile based build system that my users feel is working too slowly. For the sake of this question lets define performance as the time it takes make to figur

Answer 1

Since you're interested in the time it takes Make to decide what to do, rather than do it, you should look into options for getting Make to not actually do things:

• -q (question) will have it simply decide what has to be done, do nothing, print nothing, but return an exit status code indicating whether anything has to be done. You could simply time this for any target you're interested in (including "all").
• -n (no-op) will have it print the recipes, rather than execute them. Watching them scroll by will give you a general sense of how Make is spending its time, and if you like you can do clever piping tricks to time the process.
• -t (touch) will have it touch the target files that need to be rebuilt, instead of actually rebuilding them. A script could then look at the update times on the files, find the big gaps and tell you which targets required a lot of forethought.

EDIT:

I WAS WRONG.

Make constructs the DAG and decides which targets must be rebuilt before it rebuilds any of them. So once it starts executing rules, printing recipes or touching files, the part of the job we're interested in is over, and the observable timing is worthless.So the -n and -t options are no good, but -q is still useful as a coarse tool. Also -d will tell you Make's thought process; it won't tell you timing, but it will indicate which targets require many steps to consider.