[LLVMdev] RFC: Upcoming Build System Changes

Óscar Fuentes ofv at wanadoo.es
Wed Nov 2 08:26:51 PDT 2011

John Criswell <criswell at illinois.edu> writes:

> Autoconf + GMake:
> 16: 1681.512u 189.706s  2:48.96 1107.4%      0+0k 0+0io 0pf+0w
> 32: 1698.817u 209.073s  2:02.88 1552.6%      0+0k 0+0io 0pf+0w
> CMake:
> 32: 1700.340u 222.174s 1:38.27 1956.3%      0+0k 0+0io 0pf+0w

Thanks, John.

The cmake build is much more parallel:

 16-core make : 1107%,
 32-core make : 1552%
 32-core cmake: 1956%

I assume that on the cmake trials the note about two cores used by other
processes still applies. So the 32-core cmake build scales almost
linearly against the 16-core make build.

The 1956% CPU usage is far from the optimum 3000% that we could
expect. I think there is a I/O bottleneck due to the large object files
and libraries generated in debug mode and the huge executables that
results from them. I suspect that a release build may be faster.

Thanks again.

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