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DragonFly users List (threaded) for 2005-07
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Re: Remove unsed KQUEUE from usr.bin/make?

From: Garance A Drosihn <drosih@xxxxxxx>
Date: Thu, 7 Jul 2005 15:06:59 -0400

At 2:12 PM +0100 7/7/05, Hiten Pandya wrote:
Max Okumoto wrote:

Does anyone object if I remove the KQUEUE code from make. It is not used, and it does not improve performance. Or at least the comments in the code indicate that it does not.

Max, wasn't it made to work in FreeBSD lately? I think either jmg@xxxxxxxxxxx or phk@xxxxxxxxxxx tried to make it work; but I am not sure about this.

It works fine in freebsd 5.x, at least. I don't remember if the changes made it back to 4.x (ie, it might be that the version of `make' in dragonfly already has all the important fixes for KQUEUE).

Once we got it working, benchmarks showed that it didn't make
all that much of a performance difference.  It turned out
there was some other change which had been made which greatly
improved performance for the non-KQUEUE case.  I am pretty
sure it was:


Revision 1.86:

  Install a SIGCHLD handler so select(2) will be interrupted when
  a child terminates.  Without this patch, 'make -j1 buildworld'
  takes about 30% longer than 'make -B buildworld' on my 2.4 GHz
  P4; the difference is probably even larger on faster systems.
  With this patch, there is no perceptible difference in wall
  time between the two.

A later update moved the SIGCHLD handler to job.c

It was decided to leave the KQUEUE code in there, but not turn
it on by default.  It seemed like a good way to stress-test
KQUEUE processing if we wanted to have one.  This SIGCHLD change
was also MFC'ed to 4.x-release in Dec 2003, so I'm pretty sure
that Dragonfly would have this fix for performance of -j.

Personally, I'd like to see make-KQUEUE default to ON in
freebsd-current, just so that KQUEUE would always be
stress-tested on the bleeding edge...  :-)

Garance Alistair Drosehn            =   gad@xxxxxxxxxxxxxxxxxxxx
Senior Systems Programmer           or  gad@xxxxxxxxxxx
Rensselaer Polytechnic Institute    or  drosih@xxxxxxx

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