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Add support for profiling/debugging interpreted/JITted code
This commit builds on previous work for getting GDB support for JITted and interpreted code working in cling. It adds a JIT event listener as well to create perf map files to allow profiling of interpreted/JITted code with cling. The functionality provided is disabled by default. The interface to enable it has been chosen to be via environment variables to allow both interpreted code in the prompt as well as linked code to be able to optionally enable debugging/profiling. Using ld.so as example, where LD_DEBUG and LD_PROFILE exist, we chose CLING_DEBUG and CLING_PROFILE to enable these features. For the moment, setting these variables to anything enables the feature. Later on, if support for oprofile is added, for example, it may be better to enable specific JIT event listeners depending on the value of the variables, for example with CLING_PROFILE=perf or CLING_PROFILE=oprofile, respectively.
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129
interpreter/cling/lib/Interpreter/PerfJITEventListener.cpp
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| //--------------------------------------------------------------------*- C++ -*- | ||
| // CLING - the C++ LLVM-based InterpreterG :) | ||
| // author: Guilherme Amadio <[email protected]> | ||
| // | ||
| // This file is dual-licensed: you can choose to license it under the University | ||
| // of Illinois Open Source License or the GNU Lesser General Public License. See | ||
| // LICENSE.TXT for details. | ||
| //------------------------------------------------------------------------------ | ||
| // | ||
| // This file implements a JITEventListener object that tells perf about JITted | ||
| // symbols using perf map files (/tmp/perf-%d.map, where %d = pid of process). | ||
| // | ||
| // Documentation for this perf jit interface is available at: | ||
| // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt | ||
| // | ||
| //------------------------------------------------------------------------------ | ||
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| #ifdef __linux__ | ||
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| #include "llvm/Config/config.h" | ||
| #include "llvm/ExecutionEngine/JITEventListener.h" | ||
| #include "llvm/Object/ObjectFile.h" | ||
| #include "llvm/Object/SymbolSize.h" | ||
| #include "llvm/Support/ManagedStatic.h" | ||
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| #include <cstdint> | ||
| #include <cstdio> | ||
| #include <mutex> | ||
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| #include <unistd.h> | ||
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| using namespace llvm; | ||
| using namespace llvm::object; | ||
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| namespace { | ||
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| class PerfJITEventListener : public JITEventListener { | ||
| public: | ||
| PerfJITEventListener(); | ||
| ~PerfJITEventListener() { | ||
| if (m_Perfmap) | ||
| fclose(m_Perfmap); | ||
| } | ||
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| void notifyObjectLoaded(ObjectKey K, const ObjectFile& Obj, | ||
| const RuntimeDyld::LoadedObjectInfo& L) override; | ||
| void notifyFreeingObject(ObjectKey K) override; | ||
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| private: | ||
| std::mutex m_Mutex; | ||
| FILE* m_Perfmap; | ||
| }; | ||
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| PerfJITEventListener::PerfJITEventListener() { | ||
| char filename[64]; | ||
| snprintf(filename, 64, "/tmp/perf-%d.map", getpid()); | ||
| m_Perfmap = fopen(filename, "a"); | ||
| } | ||
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| void PerfJITEventListener::notifyObjectLoaded( | ||
| ObjectKey K, const ObjectFile& Obj, | ||
| const RuntimeDyld::LoadedObjectInfo& L) { | ||
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| if (!m_Perfmap) | ||
| return; | ||
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| OwningBinary<ObjectFile> DebugObjOwner = L.getObjectForDebug(Obj); | ||
| const ObjectFile& DebugObj = *DebugObjOwner.getBinary(); | ||
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| // For each symbol, we want to check its address and size | ||
| // if it's a function and write the information to the perf | ||
| // map file, otherwise we just ignore the symbol and any | ||
| // related errors. This implementation is adapted from LLVM: | ||
| // llvm/src/lib/ExecutionEngine/PerfJITEvents/PerfJITEventListener.cpp | ||
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| for (const std::pair<SymbolRef, uint64_t>& P : | ||
| computeSymbolSizes(DebugObj)) { | ||
| SymbolRef Sym = P.first; | ||
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| Expected<SymbolRef::Type> SymTypeOrErr = Sym.getType(); | ||
| if (!SymTypeOrErr) { | ||
| consumeError(SymTypeOrErr.takeError()); | ||
| continue; | ||
| } | ||
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| SymbolRef::Type SymType = *SymTypeOrErr; | ||
| if (SymType != SymbolRef::ST_Function) | ||
| continue; | ||
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| Expected<StringRef> Name = Sym.getName(); | ||
| if (!Name) { | ||
| consumeError(Name.takeError()); | ||
| continue; | ||
| } | ||
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| Expected<uint64_t> AddrOrErr = Sym.getAddress(); | ||
| if (!AddrOrErr) { | ||
| consumeError(AddrOrErr.takeError()); | ||
| continue; | ||
| } | ||
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| uint64_t address = *AddrOrErr; | ||
| uint64_t size = P.second; | ||
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| if (size == 0) | ||
| continue; | ||
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| std::lock_guard<std::mutex> lock(m_Mutex); | ||
| fprintf(m_Perfmap, "%" PRIx64 " %" PRIx64 " %s\n", address, size, Name->data()); | ||
| } | ||
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| fflush(m_Perfmap); | ||
| } | ||
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| void PerfJITEventListener::notifyFreeingObject(ObjectKey K) { | ||
| // nothing to be done | ||
| } | ||
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| llvm::ManagedStatic<PerfJITEventListener> PerfListener; | ||
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| } // end anonymous namespace | ||
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| namespace cling { | ||
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| JITEventListener* createPerfJITEventListener() { return &*PerfListener; } | ||
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| } // namespace cling | ||
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| #endif |