[cmake-developers] CMake master slowdown in generation step

[Stephen Kelly]

Brad King wrote:

> Do you have timings for running CMake on KDE?

With kdelibs branch KDE/4.13:

adb96ae67e2ae5d8ab543fc60f11750a42ed0c41
(after latest optimization)
real    0m17.862s
user    0m16.817s
sys     0m1.001s

9b1abc543e9aee946e093229e1715c4b8a961514
(after previous optimization)
real    0m38.593s
user    0m37.318s
sys     0m1.254s

521b930bf4e211735842e71f1eb0018c2184a05f
(before refactor)
real    0m16.526s
user    0m15.230s
sys     0m1.202s


So, similar to the VTK result probably, and probably for the same reason of 
being a deeper graph than the previous testcase.

> The "correct first, optimize later" strategy is reasonable
> for new features, but in this case everyone pays the time
> cost whether using the new features or not.  The "optimize
> later" time has to be very soon, please.  I would like to
> see the run time for the above case to be back down to 17s
> or better.

My new optimizations make the VTK time comparable with before-refactor on my 
machine.

> We like to maintain an invariant that 'master' is always
> release-ready.  The current performance is not acceptable,
> so 'master' is not currently release-ready.  I plan to merge
> no more features to 'master' until this is resolved.  If it
> is not resolved soon, I will revert the changes from 'master'
> to make it release-ready again.  Then the target SOURCES
> features can be restored after implementing with acceptable
> performance.

Ok.

Thanks,

Steve.