I've been running some experiments on building platforms in parallel and I was
wondering if folks are interested in supporting this? It is currently possible
to multi-thread a platform build by passing in `-n THREADNUMBER`, but if you
want to do something like have a top level makefile that builds all the
platforms you have to add .NOTPARALLEL: to the GNU makefile and build each
platform one after the other. Thus all the data base construction, and FD
creation happen serially.
The 1st thing you have to do to make this all work is pass --conf=${CONF_DIR}
to the build commands. The CONF_DIR can just be a copy of the Current Conf/ dir
that is placed in the build output directory. Basically this gives each
platform a separate Conf/.cache/.
But you start running into a few issues.
1) BaseTools/BuildEnv blows up if you run it in parallel.
I worked around this by commenting out RestorePreviousConfiguration, and
StoreCurrentConfiguration calls.
2) BaseTools/Source/C/GNUmakefile and Source/C/VfrCompile/GNUmakefile do not
support parallel build.
Adding .NOTPARALLEL: to these makefiles fixes this.
My top level makefile will build the BaseTools, if needed, and all the Platform
targets depend on that. This way the BaseTools only get built once. The
platform targets called out by the top level makefile had to be update to pass
--conf=${CONF_DIR} to the build command, and to create the directory in the 1st
place if need in the build output.
#1 maybe it would be best to cleanup BaseTools/BuildEnv to never use a temp
file? I also wonder if we still need support for the BaseTools and edk2 being
in separate locations, since the BaseTools are now maintained in the same repo?
For me I've been burned by this behavior, and never used it for development. So
it is kind of an enhancement. The burn was having a couple of different trees
on my system and setting up environment variables that point the tools at the
wrong tree.
#2 Adding the .NOTPARALLEL: to the BaseTools GNUmakefiles is a backwards
compatible work around. At some point we could restructure the makefiles to
support parallel build, but that may only save a few seconds.
#3 Someone could look a nmake as I've only looked at GNU make.
Thanks,
Andrew Fish
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