[llvm-commits] [PATCH] Add MSVC multi processor compilation to build system

[Erik Olofsson]

> -----Original Message-----
> From: Francois Pichet [mailto:pichet2000 at gmail.com]
> On Tue, Mar 1, 2011 at 10:36 PM, Erik Olofsson <Erik.Olofsson at hansoft.se>
> wrote:
> >
> > I was building in Debug mode so tblgen in Release mode would probably
> help a lot, but one tblgen project includes to several tblgen, this gives room
> for improvement on msbuild where they are all run sequentially in each
> project.
> >
> > Regards,
> > Erik
>
> hi
>
> Using MSVC 2010 and quadcore.
>
> Complete build (release) trunk: 14 mins 45 secs Complete build (release)
> trunk + patch: 14mins 40 secs
>
> It is within the margin of error here.
>
> so to me this patch doesn't speed things up. Builds are already multi-
> processor on a per project basis.

That is curious, as for large part of the compilation only one or two cores are utilized without /MP. It is expected to some degree as it's much easier to saturate 4 cores than 8 hyper threaded cores (16 threads). Depending on if your CPU is hyper threaded or not I would suspect you may be IO bound.

cmake -DLLVM_TARGETS_TO_BUILD="all" -DLLVM_COMPILER_JOBS=1 ../llvm
Complete build (Release) trunk: 09 mins 59 seconds
Change Lexer.h: 02 minutes 14 seconds
CPU utilization graph: http://www.olofsson.info/clang/Release-CPU-utilization.gif

cmake -DLLVM_TARGETS_TO_BUILD="all" -DLLVM_COMPILER_JOBS=0 ../llvm
Complete build (Release) trunk: 03 mins 29 seconds
Change Lexer.h: 41 seconds
CPU utilization graph: http://www.olofsson.info/clang/Release-MP-CPU-utilization.gif

cmake -DLLVM_TARGETS_TO_BUILD="all" -DLLVM_COMPILER_JOBS=1 ../llvm
Complete build (Debug) trunk: 12 mins 29 seconds
Change Lexer.h: 2 mins 2 seconds
CPU utilization graph: http://www.olofsson.info/clang/Debug-CPU-utilization.gif

cmake -DLLVM_TARGETS_TO_BUILD="all" -DLLVM_COMPILER_JOBS=0 ../llvm
Complete build (Debug) trunk: 7 mins 41 seconds
Change Lexer.h: 51 seconds
CPU utilization graph: http://www.olofsson.info/clang/Debug-MP-CPU-utilization.gif

If you look at http://www.olofsson.info/clang/Release-CPU-utilization.gif you can see the areas where only one or two cores are utilized. It would be interesting to see such graphs for your builds.

Regards,
Erik