| /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- |
| * vim: set ts=8 sts=4 et sw=4 tw=99: |
| * This Source Code Form is subject to the terms of the Mozilla Public |
| * License, v. 2.0. If a copy of the MPL was not distributed with this |
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| |
| #ifndef vm_SPSProfiler_h |
| #define vm_SPSProfiler_h |
| |
| #include "mozilla/DebugOnly.h" |
| #include "mozilla/GuardObjects.h" |
| |
| #include <stddef.h> |
| |
| #include "jslock.h" |
| #include "jsscript.h" |
| |
| #include "js/ProfilingStack.h" |
| |
| /* |
| * SPS Profiler integration with the JS Engine |
| * https://developer.mozilla.org/en/Performance/Profiling_with_the_Built-in_Profiler |
| * |
| * The SPS profiler (found in tools/profiler) is an implementation of a profiler |
| * which has the ability to walk the C++ stack as well as use instrumentation to |
| * gather information. When dealing with JS, however, SPS needs integration |
| * with the engine because otherwise it is very difficult to figure out what |
| * javascript is executing. |
| * |
| * The current method of integration with SPS is a form of instrumentation: |
| * every time a JS function is entered, a bit of information is pushed onto a |
| * stack that SPS owns and maintains. This information is then popped at the end |
| * of the JS function. SPS informs the JS engine of this stack at runtime, and |
| * it can by turned on/off dynamically. |
| * |
| * The SPS stack has three parameters: a base pointer, a size, and a maximum |
| * size. The stack is the ProfileEntry stack which will have information written |
| * to it. The size location is a pointer to an integer which represents the |
| * current size of the stack (number of valid frames). This size will be |
| * modified when JS functions are called. The maximum specified is the maximum |
| * capacity of the ProfileEntry stack. |
| * |
| * Throughout execution, the size of the stack recorded in memory may exceed the |
| * maximum. The JS engine will not write any information past the maximum limit, |
| * but it will still maintain the size of the stack. SPS code is aware of this |
| * and iterates the stack accordingly. |
| * |
| * There is some information pushed on the SPS stack for every JS function that |
| * is entered. First is a char* pointer of a description of what function was |
| * entered. Currently this string is of the form "function (file:line)" if |
| * there's a function name, or just "file:line" if there's no function name |
| * available. The other bit of information is the relevant C++ (native) stack |
| * pointer. This stack pointer is what enables the interleaving of the C++ and |
| * the JS stack. Finally, throughout execution of the function, some extra |
| * information may be updated on the ProfileEntry structure. |
| * |
| * = Profile Strings |
| * |
| * The profile strings' allocations and deallocation must be carefully |
| * maintained, and ideally at a very low overhead cost. For this reason, the JS |
| * engine maintains a mapping of all known profile strings. These strings are |
| * keyed in lookup by a JSScript*, but are serialized with a JSFunction*, |
| * JSScript* pair. A JSScript will destroy its corresponding profile string when |
| * the script is finalized. |
| * |
| * For this reason, a char* pointer pushed on the SPS stack is valid only while |
| * it is on the SPS stack. SPS uses sampling to read off information from this |
| * instrumented stack, and it therefore copies the string byte for byte when a |
| * JS function is encountered during sampling. |
| * |
| * = Native Stack Pointer |
| * |
| * The actual value pushed as the native pointer is nullptr for most JS |
| * functions. The reason for this is that there's actually very little |
| * correlation between the JS stack and the C++ stack because many JS functions |
| * all run in the same C++ frame, or can even go backwards in C++ when going |
| * from the JIT back to the interpreter. |
| * |
| * To alleviate this problem, all JS functions push nullptr as their "native |
| * stack pointer" to indicate that it's a JS function call. The function |
| * RunScript(), however, pushes an actual C++ stack pointer onto the SPS stack. |
| * This way when interleaving C++ and JS, if SPS sees a nullptr native stack |
| * pointer on the SPS stack, it looks backwards for the first non-nullptr |
| * pointer and uses that for all subsequent nullptr native stack pointers. |
| * |
| * = Line Numbers |
| * |
| * One goal of sampling is to get both a backtrace of the JS stack, but also |
| * know where within each function on the stack execution currently is. For |
| * this, each ProfileEntry has a 'pc' field to tell where its execution |
| * currently is. This field is updated whenever a call is made to another JS |
| * function, and for the JIT it is also updated whenever the JIT is left. |
| * |
| * This field is in a union with a uint32_t 'line' so that C++ can make use of |
| * the field as well. It was observed that tracking 'line' via PCToLineNumber in |
| * JS was far too expensive, so that is why the pc instead of the translated |
| * line number is stored. |
| * |
| * As an invariant, if the pc is nullptr, then the JIT is currently executing |
| * generated code. Otherwise execution is in another JS function or in C++. With |
| * this in place, only the top entry of the stack can ever have nullptr as its |
| * pc. Additionally with this invariant, it is possible to maintain mappings of |
| * JIT code to pc which can be accessed safely because they will only be |
| * accessed from a signal handler when the JIT code is executing. |
| */ |
| |
| namespace js { |
| |
| typedef HashMap<JSScript*, const char*, DefaultHasher<JSScript*>, SystemAllocPolicy> |
| ProfileStringMap; |
| |
| class AutoSPSEntry; |
| class SPSEntryMarker; |
| class SPSBaselineOSRMarker; |
| |
| class SPSProfiler |
| { |
| friend class AutoSPSEntry; |
| friend class SPSEntryMarker; |
| friend class SPSBaselineOSRMarker; |
| |
| JSRuntime* rt; |
| ProfileStringMap strings; |
| ProfileEntry* stack_; |
| uint32_t* size_; |
| uint32_t max_; |
| bool slowAssertions; |
| uint32_t enabled_; |
| PRLock* lock_; |
| void (*eventMarker_)(const char*); |
| |
| const char* allocProfileString(JSScript* script, JSFunction* function); |
| void push(const char* string, void* sp, JSScript* script, jsbytecode* pc, bool copy, |
| ProfileEntry::Category category = ProfileEntry::Category::JS); |
| void pop(); |
| |
| public: |
| explicit SPSProfiler(JSRuntime* rt); |
| ~SPSProfiler(); |
| |
| bool init(); |
| |
| uint32_t** addressOfSizePointer() { |
| return &size_; |
| } |
| |
| uint32_t* addressOfMaxSize() { |
| return &max_; |
| } |
| |
| ProfileEntry** addressOfStack() { |
| return &stack_; |
| } |
| |
| uint32_t* sizePointer() { return size_; } |
| uint32_t maxSize() { return max_; } |
| uint32_t size() { MOZ_ASSERT(installed()); return *size_; } |
| ProfileEntry* stack() { return stack_; } |
| |
| /* management of whether instrumentation is on or off */ |
| bool enabled() { MOZ_ASSERT_IF(enabled_, installed()); return enabled_; } |
| bool installed() { return stack_ != nullptr && size_ != nullptr; } |
| void enable(bool enabled); |
| void enableSlowAssertions(bool enabled) { slowAssertions = enabled; } |
| bool slowAssertionsEnabled() { return slowAssertions; } |
| |
| /* |
| * Functions which are the actual instrumentation to track run information |
| * |
| * - enter: a function has started to execute |
| * - updatePC: updates the pc information about where a function |
| * is currently executing |
| * - exit: this function has ceased execution, and no further |
| * entries/exits will be made |
| */ |
| bool enter(JSContext* cx, JSScript* script, JSFunction* maybeFun); |
| void exit(JSScript* script, JSFunction* maybeFun); |
| void updatePC(JSScript* script, jsbytecode* pc) { |
| if (enabled() && *size_ - 1 < max_) { |
| MOZ_ASSERT(*size_ > 0); |
| MOZ_ASSERT(stack_[*size_ - 1].script() == script); |
| stack_[*size_ - 1].setPC(pc); |
| } |
| } |
| |
| /* Enter asm.js code */ |
| void beginPseudoJS(const char* string, void* sp); |
| void endPseudoJS() { pop(); } |
| |
| jsbytecode* ipToPC(JSScript* script, size_t ip) { return nullptr; } |
| |
| void setProfilingStack(ProfileEntry* stack, uint32_t* size, uint32_t max); |
| void setEventMarker(void (*fn)(const char*)); |
| const char* profileString(JSScript* script, JSFunction* maybeFun); |
| void onScriptFinalized(JSScript* script); |
| |
| void markEvent(const char* event); |
| |
| /* meant to be used for testing, not recommended to call in normal code */ |
| size_t stringsCount(); |
| void stringsReset(); |
| |
| uint32_t* addressOfEnabled() { |
| return &enabled_; |
| } |
| }; |
| |
| /* |
| * This class is used to make sure the strings table |
| * is only accessed on one thread at a time. |
| */ |
| class AutoSPSLock |
| { |
| public: |
| explicit AutoSPSLock(PRLock* lock) |
| { |
| MOZ_ASSERT(lock, "Parameter should not be null!"); |
| lock_ = lock; |
| PR_Lock(lock); |
| } |
| ~AutoSPSLock() { PR_Unlock(lock_); } |
| |
| private: |
| PRLock* lock_; |
| }; |
| |
| /* |
| * This class is used to suppress profiler sampling during |
| * critical sections where stack state is not valid. |
| */ |
| class MOZ_RAII AutoSuppressProfilerSampling |
| { |
| public: |
| explicit AutoSuppressProfilerSampling(JSContext* cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM); |
| explicit AutoSuppressProfilerSampling(JSRuntime* rt MOZ_GUARD_OBJECT_NOTIFIER_PARAM); |
| |
| ~AutoSuppressProfilerSampling(); |
| |
| private: |
| JSRuntime* rt_; |
| bool previouslyEnabled_; |
| MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER |
| }; |
| |
| inline size_t |
| SPSProfiler::stringsCount() |
| { |
| AutoSPSLock lock(lock_); |
| return strings.count(); |
| } |
| |
| inline void |
| SPSProfiler::stringsReset() |
| { |
| AutoSPSLock lock(lock_); |
| strings.clear(); |
| } |
| |
| /* |
| * This class is used in RunScript() to push the marker onto the sampling stack |
| * that we're about to enter JS function calls. This is the only time in which a |
| * valid stack pointer is pushed to the sampling stack. |
| */ |
| class MOZ_RAII SPSEntryMarker |
| { |
| public: |
| explicit SPSEntryMarker(JSRuntime* rt, |
| JSScript* script |
| MOZ_GUARD_OBJECT_NOTIFIER_PARAM); |
| ~SPSEntryMarker(); |
| |
| private: |
| SPSProfiler* profiler; |
| mozilla::DebugOnly<uint32_t> size_before; |
| MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER |
| }; |
| |
| /* |
| * RAII class to automatically add SPS psuedo frame entries. |
| * |
| * NB: The `label` string must be statically allocated. |
| */ |
| class MOZ_NONHEAP_CLASS AutoSPSEntry |
| { |
| public: |
| explicit AutoSPSEntry(JSRuntime* rt, const char* label, |
| ProfileEntry::Category category = ProfileEntry::Category::JS |
| MOZ_GUARD_OBJECT_NOTIFIER_PARAM); |
| ~AutoSPSEntry(); |
| |
| private: |
| SPSProfiler* profiler_; |
| mozilla::DebugOnly<uint32_t> sizeBefore_; |
| MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER |
| }; |
| |
| /* |
| * This class is used in the interpreter to bound regions where the baseline JIT |
| * being entered via OSR. It marks the current top pseudostack entry as |
| * OSR-ed |
| */ |
| class MOZ_RAII SPSBaselineOSRMarker |
| { |
| public: |
| explicit SPSBaselineOSRMarker(JSRuntime* rt, bool hasSPSFrame |
| MOZ_GUARD_OBJECT_NOTIFIER_PARAM); |
| ~SPSBaselineOSRMarker(); |
| |
| private: |
| SPSProfiler* profiler; |
| mozilla::DebugOnly<uint32_t> size_before; |
| MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER |
| }; |
| |
| /* |
| * SPS is the profiling backend used by the JS engine to enable time profiling. |
| * More information can be found in vm/SPSProfiler.{h,cpp}. This class manages |
| * the instrumentation portion of the profiling for JIT code. |
| * |
| * The instrumentation tracks entry into functions, leaving those functions via |
| * a function call, reentering the functions from a function call, and exiting |
| * the functions from returning. This class also handles inline frames and |
| * manages the instrumentation which needs to be attached to them as well. |
| * |
| * The basic methods which emit instrumentation are at the end of this class, |
| * and the management functions are all described in the middle. |
| */ |
| template<class Assembler, class Register> |
| class SPSInstrumentation |
| { |
| SPSProfiler* profiler_; // Instrumentation location management |
| |
| public: |
| /* |
| * Creates instrumentation which writes information out the the specified |
| * profiler's stack and constituent fields. |
| */ |
| explicit SPSInstrumentation(SPSProfiler* profiler) : profiler_(profiler) {} |
| |
| /* Small proxies around SPSProfiler */ |
| bool enabled() { return profiler_ && profiler_->enabled(); } |
| SPSProfiler* profiler() { MOZ_ASSERT(enabled()); return profiler_; } |
| void disable() { profiler_ = nullptr; } |
| }; |
| |
| |
| /* Get a pointer to the top-most profiling frame, given the exit frame pointer. */ |
| void* GetTopProfilingJitFrame(uint8_t* exitFramePtr); |
| |
| } /* namespace js */ |
| |
| #endif /* vm_SPSProfiler_h */ |