[Mesa-dev] [PATCH 05/12] gallivm: Use LLVM global context.

[Mathias Fröhlich]

Hi Jose,

I tried to get my local llvm install again to a point where I can see
backtrace information, but still failed to get valgrind/massif to print
these nice backtraces. All of the llvm addresses are not resolved so far.

But a appart from that which gl example/test program do you run to see
that leakage?

And additionally looking at this below backtrace snippet and analyzing
the code that is called in llvm:

On Wednesday, May 14, 2014 02:45:26 you wrote:
> The problem is that when I do this, memory starts leaking for every compilation (even with LLVM 3.4):
> 
>   -> 100.00% (672B): operator new(unsigned long)
>     -> 100.00% (672B): std::_Rb_tree<llvm::EVT, llvm::EVT, std::_Identity<llvm::EVT>, llvm::EVT::compareRawBits, std::allocator<llvm::EVT> >::_M_insert_unique(llvm::EVT const&)
>       -> 100.00% (672B): llvm::SDNode::getValueTypeList(llvm::EVT)
>         -> 100.00% (672B): llvm::SelectionDAG::getVTList(llvm::EVT)

Ok, I see, this std::set in ./lib/CodeGen/SelectionDAG/SelectionDAG.cpp
holds EVT instances which have a possible pointer to
llvm::Type objects declared in llvm/IR/Type.h. And such a Type seems to reference
a LLVMContext with the 'Context' member in llvm::Type.
Since the std::set<EVT, ...>'s less operator treats EVT's to equivalent EVT's
referencing llvm::Types originating from different LLVMContext instances differently,
this grows with the LLVMContext instances around.

Ok, a correct solution inside llvm would be to prune these set entries once the
LLVMContext dies.

A workaround from our side could probably be to have a LLVMContext private to the
GL context as already suggested. That would still grow with the number of GL contexts.
But that is a way more unlikely use pattern for an application to create magnitudes
of GL contexts.
Well it is still a possible scenario, but willing to beat on a GL stack with threads
is also a possible scenario ...

I have not yet tried something, since I am not yet able to reproduce, but thoughts??

Greetings

Mathias