[cfe-dev] [llvm-dev] Disk space and RAM requirements in docs
Alex Bradbury via cfe-dev
cfe-dev at lists.llvm.org
Tue Apr 30 01:58:04 PDT 2019
On Tue, 30 Apr 2019 at 07:38, Petr Penzin via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Have anybody recently built LLVM in Debug mode within space requirements from the Getting Started doc?
> > An LLVM-only build will need about 1-3 GB of space. A full build of LLVM and Clang will need around 15-20 GB of disk space.
> From my experience this numbers looks drastically low. On FreeBSD my recent builds consumed more than 70 GB and on Linux - more than 60. I am building LLVM, Clang, and LLD with all default targets and default settings. On FreeBSD I am also building Polly. Also, building `clang-check` target adds around to 20 GB to the build directory size.
> Apologies for the long snippet, but here is top 20 lines from `du -h | sort -rh` on my FreeBSD directory (full log is attached):
> 91G build
> 40G build/bin
> 25G build/tools
> 25G build/lib
> 24G build/tools/clang
> 15G build/tools/clang/unittests
> 5.0G build/tools/clang/lib
> 3.9G build/lib/Target
> 3.1G build/tools/clang/unittests/Tooling
> 3.1G build/tools/clang/test
> 2.8G build/tools/clang/test/Tooling/Output/clang-check-mac-libcxx-fixed-compilation-db.cpp.tmp/mock-libcxx/bin
> 2.8G build/tools/clang/test/Tooling/Output/clang-check-mac-libcxx-fixed-compilation-db.cpp.tmp/mock-libcxx
> 2.8G build/tools/clang/test/Tooling/Output/clang-check-mac-libcxx-fixed-compilation-db.cpp.tmp
> 2.8G build/tools/clang/test/Tooling/Output
> 2.8G build/tools/clang/test/Tooling
> 1.9G build/tools/clang/unittests/Frontend
> 1.6G build/tools/clang/unittests/Driver
> 1.5G build/tools/clang/unittests/ASTMatchers
> 1.4G build/tools/clang/lib/StaticAnalyzer
> 1.3G build/lib/CodeGen
> Note that Clang's `unittest` and `test` directory together occupy more than 18 GB (which is about the size manual assigns for the entire build), with most of the space in `test` taken up by output of tooling tests (is that for MacOS, by the way?). Also, looks like five of the unittest directories for clang components are taking more than a gigabyte each (with Tooling using more than 3 GB).
> Is this expected or am I doing something wrong? If it is expected, should the manual be fixed?
> There are no RAM requirements in the doc, from my observation linker process on Linux or FreeBSD needs about 10 GB at the moment (and this has been growing for a while). Should this be also reflected in hardware requirements as well?
I think it would be worth strongly recommending the use of LLD or gold
to link. I've helped out a number of students/newcomers getting LLVM
to build for the first time and encountering issues due to binutils ld
OOMing is a common issue.
> And lastly is there a way to reduce the space consumption by Clang unittests and Tooling tests aside of disabling those?
Setting -DBUILD_SHARED_LIBS=True will reduce space requirements by
using shared libraries rather than static libraries. It will impact
the time taken to run LLVM and Clang tests though, due to greater
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