Re: Remove unsed KQUEUE from usr.bin/make?

[Kris Kennaway <kkenn@xxxxxxxxxxxxxxxxxx>]

On 2005-07-07, Garance A Drosihn <drosih@xxxxxxx> wrote:
> At 5:57 PM -0400 7/7/05, Kris Kennaway wrote:
>>On 2005-07-07, Garance A Drosihn <drosih@xxxxxxx> wrote:
>>
>>I use make on FreeBSD for running jobs with high levels of concurrency
>>(~100, or about ~300 if you count multiple concurrent make processes).
>>I've not benchmarked anything, but it would be a shame to remove
>>kqueue support because "it doesn't have a performance benefit"
>>without measuring it at the high end.
>
> I only benchmarked it using buildworlds.  I went from -j1 up to -j16,
> but only on a dual-processor machine.  At -j16 you're gone past the
> point where increasing -j actually causes the build to take LONGER,
> instead of shorter (well, at least on my hardware).  The advantage
> of KQUEUE vs non-KQUEUE was generally insignificant.  Under 1%, iirc.
> Someone else in FreeBSD-land did some benchmarks too, and found
> little improvement.  That is why make is compiled without KQUEUE
> by default.  More benchmarks would be interesting, and good to do.

You're benchmarking compilation, not make overhead.  My concurrent
make use dispatches shell scripts which sleep a lot and individually
do not use much CPU, thus make overhead becomes more important.

Kris