| // Copyright 2018 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "base/sampling_heap_profiler/sampling_heap_profiler.h" |
| |
| #include <algorithm> |
| #include <cmath> |
| #include <utility> |
| |
| #include "base/allocator/allocator_shim.h" |
| #include "base/allocator/buildflags.h" |
| #include "base/allocator/partition_allocator/partition_alloc.h" |
| #include "base/atomicops.h" |
| #include "base/macros.h" |
| #include "base/no_destructor.h" |
| #include "base/partition_alloc_buildflags.h" |
| #include "base/rand_util.h" |
| #include "base/sampling_heap_profiler/lock_free_address_hash_set.h" |
| #include "base/threading/thread_local_storage.h" |
| #include "build/build_config.h" |
| |
| #if defined(OS_MACOSX) |
| #include <pthread.h> |
| #endif |
| |
| namespace base { |
| |
| using allocator::AllocatorDispatch; |
| using subtle::Atomic32; |
| using subtle::AtomicWord; |
| |
| namespace { |
| |
| #if defined(OS_MACOSX) |
| |
| // On MacOS the implementation of libmalloc sometimes calls malloc recursively, |
| // delegating allocations between zones. That causes our hooks being called |
| // twice. The scoped guard allows us to detect that. |
| class ReentryGuard { |
| public: |
| ReentryGuard() : allowed_(!pthread_getspecific(entered_key_)) { |
| pthread_setspecific(entered_key_, reinterpret_cast<void*>(1)); |
| } |
| |
| ~ReentryGuard() { |
| if (LIKELY(allowed_)) |
| pthread_setspecific(entered_key_, reinterpret_cast<void*>(0)); |
| } |
| |
| operator bool() { return allowed_; } |
| |
| static void Init() { |
| int result = pthread_key_create(&entered_key_, nullptr); |
| DCHECK(!result); |
| } |
| |
| private: |
| bool allowed_; |
| static pthread_key_t entered_key_; |
| }; |
| |
| pthread_key_t ReentryGuard::entered_key_; |
| |
| #else |
| |
| class ReentryGuard { |
| public: |
| operator bool() { return true; } |
| static void Init() {} |
| }; |
| |
| #endif |
| |
| const size_t kDefaultSamplingIntervalBytes = 128 * 1024; |
| |
| // Controls if sample intervals should not be randomized. Used for testing. |
| bool g_deterministic; |
| |
| // A positive value if profiling is running, otherwise it's zero. |
| Atomic32 g_running; |
| |
| // Pointer to the current |LockFreeAddressHashSet|. |
| AtomicWord g_sampled_addresses_set; |
| |
| // Sampling interval parameter, the mean value for intervals between samples. |
| AtomicWord g_sampling_interval = kDefaultSamplingIntervalBytes; |
| |
| void (*g_hooks_install_callback)(); |
| Atomic32 g_hooks_installed; |
| |
| void* AllocFn(const AllocatorDispatch* self, size_t size, void* context) { |
| ReentryGuard guard; |
| void* address = self->next->alloc_function(self->next, size, context); |
| if (LIKELY(guard)) { |
| PoissonAllocationSampler::RecordAlloc( |
| address, size, PoissonAllocationSampler::kMalloc, nullptr); |
| } |
| return address; |
| } |
| |
| void* AllocZeroInitializedFn(const AllocatorDispatch* self, |
| size_t n, |
| size_t size, |
| void* context) { |
| ReentryGuard guard; |
| void* address = |
| self->next->alloc_zero_initialized_function(self->next, n, size, context); |
| if (LIKELY(guard)) { |
| PoissonAllocationSampler::RecordAlloc( |
| address, n * size, PoissonAllocationSampler::kMalloc, nullptr); |
| } |
| return address; |
| } |
| |
| void* AllocAlignedFn(const AllocatorDispatch* self, |
| size_t alignment, |
| size_t size, |
| void* context) { |
| ReentryGuard guard; |
| void* address = |
| self->next->alloc_aligned_function(self->next, alignment, size, context); |
| if (LIKELY(guard)) { |
| PoissonAllocationSampler::RecordAlloc( |
| address, size, PoissonAllocationSampler::kMalloc, nullptr); |
| } |
| return address; |
| } |
| |
| void* ReallocFn(const AllocatorDispatch* self, |
| void* address, |
| size_t size, |
| void* context) { |
| ReentryGuard guard; |
| // Note: size == 0 actually performs free. |
| PoissonAllocationSampler::RecordFree(address); |
| address = self->next->realloc_function(self->next, address, size, context); |
| if (LIKELY(guard)) { |
| PoissonAllocationSampler::RecordAlloc( |
| address, size, PoissonAllocationSampler::kMalloc, nullptr); |
| } |
| return address; |
| } |
| |
| void FreeFn(const AllocatorDispatch* self, void* address, void* context) { |
| // Note: The RecordFree should be called before free_function |
| // (here and in other places). |
| // That is because we need to remove the recorded allocation sample before |
| // free_function, as once the latter is executed the address becomes available |
| // and can be allocated by another thread. That would be racy otherwise. |
| PoissonAllocationSampler::RecordFree(address); |
| self->next->free_function(self->next, address, context); |
| } |
| |
| size_t GetSizeEstimateFn(const AllocatorDispatch* self, |
| void* address, |
| void* context) { |
| return self->next->get_size_estimate_function(self->next, address, context); |
| } |
| |
| unsigned BatchMallocFn(const AllocatorDispatch* self, |
| size_t size, |
| void** results, |
| unsigned num_requested, |
| void* context) { |
| ReentryGuard guard; |
| unsigned num_allocated = self->next->batch_malloc_function( |
| self->next, size, results, num_requested, context); |
| if (LIKELY(guard)) { |
| for (unsigned i = 0; i < num_allocated; ++i) { |
| PoissonAllocationSampler::RecordAlloc( |
| results[i], size, PoissonAllocationSampler::kMalloc, nullptr); |
| } |
| } |
| return num_allocated; |
| } |
| |
| void BatchFreeFn(const AllocatorDispatch* self, |
| void** to_be_freed, |
| unsigned num_to_be_freed, |
| void* context) { |
| for (unsigned i = 0; i < num_to_be_freed; ++i) |
| PoissonAllocationSampler::RecordFree(to_be_freed[i]); |
| self->next->batch_free_function(self->next, to_be_freed, num_to_be_freed, |
| context); |
| } |
| |
| void FreeDefiniteSizeFn(const AllocatorDispatch* self, |
| void* address, |
| size_t size, |
| void* context) { |
| PoissonAllocationSampler::RecordFree(address); |
| self->next->free_definite_size_function(self->next, address, size, context); |
| } |
| |
| AllocatorDispatch g_allocator_dispatch = {&AllocFn, |
| &AllocZeroInitializedFn, |
| &AllocAlignedFn, |
| &ReallocFn, |
| &FreeFn, |
| &GetSizeEstimateFn, |
| &BatchMallocFn, |
| &BatchFreeFn, |
| &FreeDefiniteSizeFn, |
| nullptr}; |
| |
| #if BUILDFLAG(USE_PARTITION_ALLOC) && !defined(OS_NACL) |
| |
| void PartitionAllocHook(void* address, size_t size, const char* type) { |
| PoissonAllocationSampler::RecordAlloc( |
| address, size, PoissonAllocationSampler::kPartitionAlloc, type); |
| } |
| |
| void PartitionFreeHook(void* address) { |
| PoissonAllocationSampler::RecordFree(address); |
| } |
| |
| #endif // BUILDFLAG(USE_PARTITION_ALLOC) && !defined(OS_NACL) |
| |
| ThreadLocalStorage::Slot& AccumulatedBytesTLS() { |
| static NoDestructor<ThreadLocalStorage::Slot> accumulated_bytes_tls; |
| return *accumulated_bytes_tls; |
| } |
| |
| } // namespace |
| |
| PoissonAllocationSampler::MuteThreadSamplesScope::MuteThreadSamplesScope() { |
| CHECK(!Get()->entered_.Get()); |
| Get()->entered_.Set(true); |
| } |
| |
| PoissonAllocationSampler::MuteThreadSamplesScope::~MuteThreadSamplesScope() { |
| CHECK(Get()->entered_.Get()); |
| Get()->entered_.Set(false); |
| } |
| |
| PoissonAllocationSampler* PoissonAllocationSampler::instance_; |
| |
| PoissonAllocationSampler::PoissonAllocationSampler() { |
| instance_ = this; |
| auto sampled_addresses = std::make_unique<LockFreeAddressHashSet>(64); |
| subtle::NoBarrier_Store( |
| &g_sampled_addresses_set, |
| reinterpret_cast<AtomicWord>(sampled_addresses.get())); |
| sampled_addresses_stack_.push_back(std::move(sampled_addresses)); |
| } |
| |
| // static |
| void PoissonAllocationSampler::Init() { |
| // Preallocate the TLS slot early, so it can't cause reentracy issues |
| // when sampling is started. |
| ignore_result(AccumulatedBytesTLS().Get()); |
| ReentryGuard::Init(); |
| } |
| |
| // static |
| void PoissonAllocationSampler::InstallAllocatorHooksOnce() { |
| static bool hook_installed = InstallAllocatorHooks(); |
| ignore_result(hook_installed); |
| } |
| |
| // static |
| bool PoissonAllocationSampler::InstallAllocatorHooks() { |
| #if BUILDFLAG(USE_ALLOCATOR_SHIM) |
| allocator::InsertAllocatorDispatch(&g_allocator_dispatch); |
| #else |
| ignore_result(g_allocator_dispatch); |
| DLOG(WARNING) |
| << "base::allocator shims are not available for memory sampling."; |
| #endif // BUILDFLAG(USE_ALLOCATOR_SHIM) |
| |
| #if BUILDFLAG(USE_PARTITION_ALLOC) && !defined(OS_NACL) |
| PartitionAllocHooks::SetAllocationHook(&PartitionAllocHook); |
| PartitionAllocHooks::SetFreeHook(&PartitionFreeHook); |
| #endif // BUILDFLAG(USE_PARTITION_ALLOC) && !defined(OS_NACL) |
| |
| int32_t hooks_install_callback_has_been_set = |
| subtle::Acquire_CompareAndSwap(&g_hooks_installed, 0, 1); |
| if (hooks_install_callback_has_been_set) |
| g_hooks_install_callback(); |
| |
| return true; |
| } |
| |
| // static |
| void PoissonAllocationSampler::SetHooksInstallCallback( |
| void (*hooks_install_callback)()) { |
| CHECK(!g_hooks_install_callback && hooks_install_callback); |
| g_hooks_install_callback = hooks_install_callback; |
| |
| int32_t profiler_has_already_been_initialized = |
| subtle::Release_CompareAndSwap(&g_hooks_installed, 0, 1); |
| if (profiler_has_already_been_initialized) |
| g_hooks_install_callback(); |
| } |
| |
| void PoissonAllocationSampler::Start() { |
| InstallAllocatorHooksOnce(); |
| subtle::Barrier_AtomicIncrement(&g_running, 1); |
| } |
| |
| void PoissonAllocationSampler::Stop() { |
| AtomicWord count = subtle::Barrier_AtomicIncrement(&g_running, -1); |
| CHECK_GE(count, 0); |
| } |
| |
| void PoissonAllocationSampler::SetSamplingInterval(size_t sampling_interval) { |
| // TODO(alph): Reset the sample being collected if running. |
| subtle::Release_Store(&g_sampling_interval, |
| static_cast<AtomicWord>(sampling_interval)); |
| } |
| |
| // static |
| size_t PoissonAllocationSampler::GetNextSampleInterval(size_t interval) { |
| if (UNLIKELY(g_deterministic)) |
| return interval; |
| |
| // We sample with a Poisson process, with constant average sampling |
| // interval. This follows the exponential probability distribution with |
| // parameter λ = 1/interval where |interval| is the average number of bytes |
| // between samples. |
| // Let u be a uniformly distributed random number between 0 and 1, then |
| // next_sample = -ln(u) / λ |
| double uniform = RandDouble(); |
| double value = -log(uniform) * interval; |
| size_t min_value = sizeof(intptr_t); |
| // We limit the upper bound of a sample interval to make sure we don't have |
| // huge gaps in the sampling stream. Probability of the upper bound gets hit |
| // is exp(-20) ~ 2e-9, so it should not skew the distribution. |
| size_t max_value = interval * 20; |
| if (UNLIKELY(value < min_value)) |
| return min_value; |
| if (UNLIKELY(value > max_value)) |
| return max_value; |
| return static_cast<size_t>(value); |
| } |
| |
| // static |
| void PoissonAllocationSampler::RecordAlloc(void* address, |
| size_t size, |
| AllocatorType type, |
| const char* context) { |
| if (UNLIKELY(!subtle::NoBarrier_Load(&g_running))) |
| return; |
| if (UNLIKELY(ThreadLocalStorage::HasBeenDestroyed())) |
| return; |
| |
| intptr_t accumulated_bytes = |
| reinterpret_cast<intptr_t>(AccumulatedBytesTLS().Get()); |
| accumulated_bytes += size; |
| if (LIKELY(accumulated_bytes < 0)) { |
| AccumulatedBytesTLS().Set(reinterpret_cast<void*>(accumulated_bytes)); |
| return; |
| } |
| |
| size_t mean_interval = subtle::NoBarrier_Load(&g_sampling_interval); |
| size_t samples = accumulated_bytes / mean_interval; |
| accumulated_bytes %= mean_interval; |
| |
| do { |
| accumulated_bytes -= GetNextSampleInterval(mean_interval); |
| ++samples; |
| } while (accumulated_bytes >= 0); |
| |
| AccumulatedBytesTLS().Set(reinterpret_cast<void*>(accumulated_bytes)); |
| |
| instance_->DoRecordAlloc(samples * mean_interval, size, address, type, |
| context); |
| } |
| |
| void PoissonAllocationSampler::DoRecordAlloc(size_t total_allocated, |
| size_t size, |
| void* address, |
| AllocatorType type, |
| const char* context) { |
| if (entered_.Get()) |
| return; |
| MuteThreadSamplesScope no_reentrancy_scope; |
| AutoLock lock(mutex_); |
| // TODO(alph): Sometimes RecordAlloc is called twice in a row without |
| // a RecordFree in between. Investigate it. |
| if (!sampled_addresses_set().Contains(address)) { |
| sampled_addresses_set().Insert(address); |
| BalanceAddressesHashSet(); |
| for (auto* observer : observers_) |
| observer->SampleAdded(address, size, total_allocated, type, context); |
| } |
| } |
| |
| // static |
| void PoissonAllocationSampler::RecordFree(void* address) { |
| if (UNLIKELY(address == nullptr)) |
| return; |
| if (UNLIKELY(sampled_addresses_set().Contains(address))) |
| instance_->DoRecordFree(address); |
| } |
| |
| void PoissonAllocationSampler::DoRecordFree(void* address) { |
| if (UNLIKELY(ThreadLocalStorage::HasBeenDestroyed())) |
| return; |
| if (entered_.Get()) |
| return; |
| MuteThreadSamplesScope no_reentrancy_scope; |
| AutoLock lock(mutex_); |
| for (auto* observer : observers_) |
| observer->SampleRemoved(address); |
| sampled_addresses_set().Remove(address); |
| } |
| |
| void PoissonAllocationSampler::BalanceAddressesHashSet() { |
| // Check if the load_factor of the current addresses hash set becomes higher |
| // than 1, allocate a new twice larger one, copy all the data, |
| // and switch to using it. |
| // During the copy process no other writes are made to both sets |
| // as it's behind the lock. |
| // All the readers continue to use the old one until the atomic switch |
| // process takes place. |
| LockFreeAddressHashSet& current_set = sampled_addresses_set(); |
| if (current_set.load_factor() < 1) |
| return; |
| auto new_set = |
| std::make_unique<LockFreeAddressHashSet>(current_set.buckets_count() * 2); |
| new_set->Copy(current_set); |
| // Atomically switch all the new readers to the new set. |
| subtle::Release_Store(&g_sampled_addresses_set, |
| reinterpret_cast<AtomicWord>(new_set.get())); |
| // We still have to keep all the old maps alive to resolve the theoretical |
| // race with readers in |RecordFree| that have already obtained the map, |
| // but haven't yet managed to access it. |
| sampled_addresses_stack_.push_back(std::move(new_set)); |
| } |
| |
| // static |
| LockFreeAddressHashSet& PoissonAllocationSampler::sampled_addresses_set() { |
| return *reinterpret_cast<LockFreeAddressHashSet*>( |
| subtle::NoBarrier_Load(&g_sampled_addresses_set)); |
| } |
| |
| // static |
| PoissonAllocationSampler* PoissonAllocationSampler::Get() { |
| static NoDestructor<PoissonAllocationSampler> instance; |
| return instance.get(); |
| } |
| |
| // static |
| void PoissonAllocationSampler::SuppressRandomnessForTest(bool suppress) { |
| g_deterministic = suppress; |
| } |
| |
| void PoissonAllocationSampler::AddSamplesObserver(SamplesObserver* observer) { |
| MuteThreadSamplesScope no_reentrancy_scope; |
| AutoLock lock(mutex_); |
| observers_.push_back(observer); |
| } |
| |
| void PoissonAllocationSampler::RemoveSamplesObserver( |
| SamplesObserver* observer) { |
| MuteThreadSamplesScope no_reentrancy_scope; |
| AutoLock lock(mutex_); |
| auto it = std::find(observers_.begin(), observers_.end(), observer); |
| CHECK(it != observers_.end()); |
| observers_.erase(it); |
| } |
| |
| } // namespace base |