603214 - Build NSPR in parallel

Status: RESOLVED FIXED

(NSPR :: NSPR, enhancement)

Description

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Attachment: Patch

This patch drops the time to build NSPR on my system from 35s to 7.5s (500% increase in speed).  The only complex target I saw is nspr4, if my eyes aren't deceiving me all the rest only use object files from one directory.

Comment 1

[Wan-Teh Chang]

khuey: Thanks for the patch.  Please add a comment to explain why adding a 'build' makefile target fixes the problem.

+export::
+	$(MAKE) -C . build

You should be able to omit "-C .", right?

Can you write this makefile rule as follows?

export:: build

Comment 2

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

No.  In a parallel make, all of the dependencies of a target are executed concurrently (up to the N maximum jobs from -jN).  The instructions for a target, are however, executed sequentially.  By moving the final linking of nspr4 to an additional target we can ensure that final linking occurs after we loop through the other directories (since rules.mk gets included before this).

Comment 3

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Attachment: Patch w/comment

Comment 4

[Wan-Teh Chang]

Attachment: Patch v3 by Kyle Huey

khuey: thanks for the explanation.  I understand it now.
I also compared your fix with the previous attempt in
bug 123423.  Both patches have the same idea: recurse
into $(DIRS) before building $(TARGETS).  I'm glad you
made it work.

I edited your comment and removed "-C .", which I
believe is unnecessary.  Please review this patch.

I think we can fix this in a more elegant way, but
your fix is fine (most bang for the buck).

Comment 5

[Wan-Teh Chang]

Should I change the comment to say what I summarized in comment 4?
  We use a 'build' target here to ensure that we build $(TARGETS)
  after recursing into $(DIRS) to create the object files in a
  parallel build.  ...

or

  We use a 'build' target here to ensure that we build $(TARGETS)
  after looping over $(DIRS) to create the object files in a
  parallel build.  ...

Comment 6

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Comment on attachment 482736 [details] [diff] [review]
Patch v3 by Kyle Huey

I prefer the second comment.

Comment 7

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

(In reply to comment #5)
>   We use a 'build' target here to ensure that we build $(TARGETS)
>   after looping over $(DIRS) to create the object files in a
>   parallel build.  ...

This one.

Comment 8

[Wan-Teh Chang]

Attachment: Patch v4 by Kyle Huey

Patch checked in on the NSPR trunk (NSPR 4.8.7).

Checking in Makefile.in;
/cvsroot/mozilla/nsprpub/Makefile.in,v  <--  Makefile.in
new revision: 1.25; previous revision: 1.24
done
Checking in pr/src/Makefile.in;
/cvsroot/mozilla/nsprpub/pr/src/Makefile.in,v  <--  Makefile.in
new revision: 1.60; previous revision: 1.59
done