Implement a ScopedThreadHeapUsage class to allow profiling per-thread heap usage.

base/debug/scoped_thread_heap_usage.cc

+// Copyright 2016 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/debug/scoped_thread_heap_usage.h"
+
+#include <stdint.h>
+#include <algorithm>
+#include <type_traits>
+
+#include "base/allocator/allocator_shim.h"
+#include "base/allocator/features.h"
+#include "base/logging.h"
+#include "base/threading/thread_local_storage.h"
+#include "build/build_config.h"
+
+#if defined(OS_MACOSX) || defined(OS_IOS)
+#include <malloc/malloc.h>
+#else
+#include <malloc.h>
+#endif
+
+namespace base {
+namespace debug {
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+ThreadLocalStorage::StaticSlot g_thread_allocator_usage = TLS_INITIALIZER;
+
+ScopedThreadHeapUsage::ThreadAllocatorUsage* const kInitializingSentinel =
+    reinterpret_cast<ScopedThreadHeapUsage::ThreadAllocatorUsage*>(-1);
+
+bool g_heap_tracking_enabled = false;
+
+// Forward declared as it needs to delegate memory allocation to the next
+// lower shim.
+ScopedThreadHeapUsage::ThreadAllocatorUsage* GetOrCreateThreadUsage();
+
+size_t GetAllocSizeEstimate(const AllocatorDispatch* next, void* ptr) {
+  if (ptr == nullptr)
+    return 0U;
+
+  return next->get_size_estimate_function(next, ptr);
+}
+
+void RecordAlloc(const AllocatorDispatch* next, void* ptr, size_t size) {
+  ScopedThreadHeapUsage::ThreadAllocatorUsage* usage = GetOrCreateThreadUsage();
+  if (usage == nullptr)
+    return;
+
+  usage->alloc_ops++;
+  size_t estimate = GetAllocSizeEstimate(next, ptr);
+  if (size && estimate) {
+    usage->alloc_bytes += estimate;
+    usage->alloc_overhead_bytes += estimate - size;
+
+    // Only keep track of the net number of bytes allocated in the scope if the
+    // size estimate function returns sane values, e.g. non-zero.
+    uint64_t allocated_bytes = usage->alloc_bytes - usage->free_bytes;
+    if (allocated_bytes > usage->max_allocated_bytes)
+      usage->max_allocated_bytes = allocated_bytes;
+  } else {
+    usage->alloc_bytes += size;
+  }
+}
+
+void RecordFree(const AllocatorDispatch* next, void* ptr) {
+  ScopedThreadHeapUsage::ThreadAllocatorUsage* usage = GetOrCreateThreadUsage();
+  if (usage == nullptr)
+    return;
+
+  size_t estimate = GetAllocSizeEstimate(next, ptr);
+  usage->free_ops++;
+  usage->free_bytes += estimate;
+}
+
+void* AllocFn(const AllocatorDispatch* self, size_t size) {
+  void* ret = self->next->alloc_function(self->next, size);
+  if (ret != nullptr)
+    RecordAlloc(self->next, ret, size);
+
+  return ret;
+}
+
+void* AllocZeroInitializedFn(const AllocatorDispatch* self,
+                             size_t n,
+                             size_t size) {
+  void* ret = self->next->alloc_zero_initialized_function(self->next, n, size);
+  if (ret != nullptr)
+    RecordAlloc(self->next, ret, size);
+
+  return ret;
+}
+
+void* AllocAlignedFn(const AllocatorDispatch* self,
+                     size_t alignment,
+                     size_t size) {
+  void* ret = self->next->alloc_aligned_function(self->next, alignment, size);
+  if (ret != nullptr)
+    RecordAlloc(self->next, ret, size);
+
+  return ret;
+}
+
+void* ReallocFn(const AllocatorDispatch* self, void* address, size_t size) {
+  if (address != nullptr)
+    RecordFree(self->next, address);
+
+  void* ret = self->next->realloc_function(self->next, address, size);
+  if (ret != nullptr && size != 0)
+    RecordAlloc(self->next, ret, size);
+
+  return ret;
+}
+
+void FreeFn(const AllocatorDispatch* self, void* address) {
+  if (address != nullptr)
+    RecordFree(self->next, address);
+  self->next->free_function(self->next, address);
+}
+
+size_t GetSizeEstimateFn(const AllocatorDispatch* self, void* address) {
+  return self->next->get_size_estimate_function(self->next, address);
+}
+
+// The allocator dispatch used to intercept heap operations.
+AllocatorDispatch allocator_dispatch = {
+    &AllocFn, &AllocZeroInitializedFn, &AllocAlignedFn, &ReallocFn,
+    &FreeFn,  &GetSizeEstimateFn,      nullptr};
+
+ScopedThreadHeapUsage::ThreadAllocatorUsage* GetOrCreateThreadUsage() {
+  ScopedThreadHeapUsage::ThreadAllocatorUsage* allocator_usage =
+      static_cast<ScopedThreadHeapUsage::ThreadAllocatorUsage*>(
+          g_thread_allocator_usage.Get());
+  if (allocator_usage == kInitializingSentinel)
+    return nullptr;  // Re-entrancy case.
+
+  if (allocator_usage == nullptr) {
+    // Prevent reentrancy due to the allocation below.
+    g_thread_allocator_usage.Set(kInitializingSentinel);
+
+    allocator_usage = new ScopedThreadHeapUsage::ThreadAllocatorUsage;
+    memset(allocator_usage, 0, sizeof(*allocator_usage));
+    g_thread_allocator_usage.Set(allocator_usage);
+  }
+
+  return allocator_usage;
+}
+
+}  // namespace
+
+ScopedThreadHeapUsage::ScopedThreadHeapUsage() {
+  // Initialize must be called before creating instances of this class.
+  CHECK(g_thread_allocator_usage.initialized());
+
+  ThreadAllocatorUsage* usage = GetOrCreateThreadUsage();
+  usage_at_creation_ = *usage;
+
+  // Reset the stats for our current scope.
+  // The per-thread usage instance now tracks this scope's usage, while this
+  // instance persists the outer scope's usage stats. On destruction, this
+  // instance will restore the outer scope's usage stats with this scope's usage
+  // added.
+  memset(usage, 0, sizeof(*usage));
+
+  static_assert(std::is_pod<ThreadAllocatorUsage>::value, "Must be POD.");
+}
+
+ScopedThreadHeapUsage::~ScopedThreadHeapUsage() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  ThreadAllocatorUsage* usage = GetOrCreateThreadUsage();
+
+  // Update the outer max.
+  if (usage->max_allocated_bytes) {
+    uint64_t outer_net_alloc_bytes =
+        usage_at_creation_.alloc_bytes - usage_at_creation_.free_bytes;
+
+    usage->max_allocated_bytes =
+        std::max(usage_at_creation_.max_allocated_bytes,
+                 outer_net_alloc_bytes + usage->max_allocated_bytes);
+  }
+
+  usage->alloc_ops += usage_at_creation_.alloc_ops;
+  usage->alloc_bytes += usage_at_creation_.alloc_bytes;
+  usage->alloc_overhead_bytes += usage_at_creation_.alloc_overhead_bytes;
+  usage->free_ops += usage_at_creation_.free_ops;
+  usage->free_bytes += usage_at_creation_.free_bytes;
+}
+
+ScopedThreadHeapUsage::ThreadAllocatorUsage ScopedThreadHeapUsage::Now() {
+  ThreadAllocatorUsage* usage = GetOrCreateThreadUsage();
+  return *usage;
+}
+
+void ScopedThreadHeapUsage::Initialize() {
+  if (!g_thread_allocator_usage.initialized()) {
+    g_thread_allocator_usage.Initialize([](void* allocator_usage) {
+      delete static_cast<ScopedThreadHeapUsage::ThreadAllocatorUsage*>(
+          allocator_usage);
+    });
+  }
+}
+
+void ScopedThreadHeapUsage::EnableHeapTracking() {
+  CHECK_EQ(false, g_heap_tracking_enabled) << "No double-enabling.";

[Nico, 2016/09/09 14:40:33]

check isn't thread-safe (doubt it matters much though)

[Primiano Tucci (use gerrit), 2016/09/09 14:56:18]

InsertAllocatorDispatch has a DCHECK(CalledOnValidThread()), which checks that
all registrations are done on the same thread (in dcheck builds).  So, even if
you manage to race on the g_tracker_enabled flag here which is not atomic, this
should hit anyway that dcheck.

[Sigurður Ásgeirsson, 2016/09/09 14:58:20]

Yeah, this is best effort.

[Sigurður Ásgeirsson, 2016/09/09 14:58:20]

Ah, nice. I figure this is a dev-time buzz only, so ought to be fine.

+  g_heap_tracking_enabled = true;
+#if BUILDFLAG(USE_EXPERIMENTAL_ALLOCATOR_SHIM)
+  base::allocator::InsertAllocatorDispatch(&allocator_dispatch);
+#else
+  CHECK(false) << "Can't enable heap tracking without the shim.";
+#endif  // BUILDFLAG(USE_EXPERIMENTAL_ALLOCATOR_SHIM)
+}
+
+void ScopedThreadHeapUsage::DisableHeapTrackingForTesting() {
+#if BUILDFLAG(USE_EXPERIMENTAL_ALLOCATOR_SHIM)
+  base::allocator::RemoveAllocatorDispatchForTesting(&allocator_dispatch);
+#else
+  CHECK(false) << "Can't disable heap tracking without the shim.";
+#endif  // BUILDFLAG(USE_EXPERIMENTAL_ALLOCATOR_SHIM)
+  DCHECK_EQ(true, g_heap_tracking_enabled) << "Heap tracking not enabled.";
+  g_heap_tracking_enabled = false;
+}
+
+base::allocator::AllocatorDispatch*
+ScopedThreadHeapUsage::GetDispatchForTesting() {
+  return &allocator_dispatch;
+}
+
+}  // namespace debug
+}  // namespace base