[LLVMdev] [cfe-dev] [llvmdev] Clang 3.6 and trunk, high RSS usage compared to GCC (12.5GB vs. 0.5GB)
David Abdurachmanov
david.abdurachmanov at gmail.com
Wed Jan 28 01:19:49 PST 2015
Hi,
It seems that we always disabled optimizer on some files for Clang and
I dropped this particular patch from our code base.
I tried to bisect Clang and went as far as 3.3 LLVM/Clang release with
the same memory consumption.
I moved to Fedora 21 based VM. GCC 4.9.2 used <500MB, and Clang 3.3 till
trunk above 10GB until VM hanged.
We didn't use --disable-assertions. Clang still has a number of issue
with our code base (incl. crashing/asserting). pre-3.6 Clang improves
(no more aborting), but some issues remain. For those I filled bug reports.
Yet to test the current 3.6 RC1 with our code base to see if it regressed
or not.
david
On Jan 27, 2015, at 4:35 PM, Milian Wolff wrote:
> On Tuesday 27 January 2015 15:19:33 David Abdurachmanov wrote:
>> 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
>
> I could reproduce this locally with clang 3.5.1 from the ArchLinux packages. I
> ran it through my heaptrack [1] tool until ~630MB peak memory where consumed,
> which should give enough of an insight already. The full report can be found
> at [2]. Here is an excerpt:
>
> 7137759 calls with 475.81MB peak consumption from:
> 0x7f83d81ff4ef
> in /usr/bin/../lib/libLLVM-3.5.so
> llvm::LazyValueInfo::getConstant(llvm::Value*, llvm::BasicBlock*)
> in /usr/bin/../lib/libLLVM-3.5.so
> 0x7f83d80ba72f
> in /usr/bin/../lib/libLLVM-3.5.so
> llvm::FPPassManager::runOnFunction(llvm::Function&)
> in /usr/bin/../lib/libLLVM-3.5.so
> 0x7f83d78df9c3
> in /usr/bin/../lib/libLLVM-3.5.so
> llvm::legacy::PassManagerImpl::run(llvm::Module&)
> in /usr/bin/../lib/libLLVM-3.5.so
> clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::CodeGenOptions
> const&, clang::TargetOptions const&, clang::LangOptions const&,
> llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::raw_ostream*)
> in /usr/bin/clang
> 0x8735a1
> in /usr/bin/clang
> clang::ParseAST(clang::Sema&, bool, bool)
> in /usr/bin/clang
> clang::CodeGenAction::ExecuteAction()
> in /usr/bin/clang
> clang::FrontendAction::Execute()
> in /usr/bin/clang
> clang::CompilerInstance::ExecuteAction(clang::FrontendAction&)
> in /usr/bin/clang
> clang::ExecuteCompilerInvocation(clang::CompilerInstance*)
> in /usr/bin/clang
> cc1_main(char const**, char const**, char const*, void*)
> in /usr/bin/clang
> main
> in /usr/bin/clang
>
> HTH
>
> [1]: http://milianw.de/blog/heaptrack-a-heap-memory-profiler-for-linux
> [2]: https://userpage.physik.fu-berlin.de/~milianw/heaptrack.clang.report.txt.gz
>
>
> --
> Milian Wolff
> mail at milianw.de
> http://milianw.de
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