[cfe-dev] [llvmdev] Clang 3.6 and trunk, high RSS usage compared to GCC (12.5GB vs. 0.5GB)

[David Abdurachmanov]

Hi,

I found that after moving to Clang pre-3.6 (git
65d8b4c4998b3a0c20934ea72ede72ef4838a004) and trunk (git
718825a8666acd9ceaab70fc7868332f20e2758f) our internal build machines started
going offline in Jenkins. Clang after 3.5 release is consuming extreme amounts
of memory in some cases.

I have uploaded [1] one of affected files.

$ g++ -std=c++11 -c -O1 -fPIC vpp_generated.ii -o vpp_generated.o

vmpeak: 582432 KB
rspeak: 504500 KB = ~ 0.5GB

$ clang++ -std=c++11 -c -O1 -fPIC vpp_generated.ii -o vpp_generated.o

vmpeak: 12992076 KB
rspeak: 12820184 KB = ~12.5GB

Disabling optimzer (-O0) resolves the issue, and RSS usage drops to ~300MB.

I decided to write here directly instead of creating yet another bug report,
which usually don't get any feedback/comments.

clang version 3.7.0 (git 718825a8666acd9ceaab70fc7868332f20e2758f)
Target: x86_64-unknown-linux-gnu
Thread model: posix

Compiled:

../configure --prefix=<..> --enable-optimized --with-binutils-include=<..>
--disable-terminfo --enable-bindings=none CC=gcc CXX=g++ 'CPP=gcc -E'
'CXXCPP=g++ -E'

Cheers,
david
- - -
[1] http://davidlt.web.cern.ch/davidlt/vault/vpp_generated.ii.xz
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