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

base/debug/scoped_heap_usage.cc

Index: base/debug/scoped_heap_usage.cc
diff --git a/base/debug/scoped_heap_usage.cc b/base/debug/scoped_heap_usage.cc
new file mode 100644
index 0000000000000000000000000000000000000000..50eadbd71fa391f34e0942bd0464e19a619aebb8
--- /dev/null
+++ b/base/debug/scoped_heap_usage.cc
@@ -0,0 +1,194 @@
+// 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_heap_usage.h"
+
+#include <malloc.h>
+#include <stdint.h>
+// TODO(siggi): DO NOT SUBMIT
+#include <windows.h>
+
+#include "base/allocator/allocator_shim.h"
+#include "base/lazy_instance.h"
+#include "base/threading/thread_local.h"
+
+namespace base {
+namespace debug {
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+base::LazyInstance<base::ThreadLocalPointer<ScopedHeapUsage::AllocatorUsage>>::
+    Leaky g_thread_allocator_usage = LAZY_INSTANCE_INITIALIZER;
+
+// Forward declared as it needs to delegate memory allocation to the next
+// lower shim.
+ScopedHeapUsage::AllocatorUsage* GetOrCreateThreadUsage();
+
+// DO NOT SUBMIT.
+// This functionality needs to be exposed on the heap shims. Note that under the
+// linux libc, it appears the heap doesn't keep track of the user size, but
+// instead allows querying the actual user size of the allocation with

[chrisha, 2016/07/21 14:23:30]

Did you mean: s/actual user size/actual size/

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

+// malloc_usable_size. I'm not sure how best to deal with this.

[chrisha, 2016/07/21 14:23:31]

Maybe by making allocated and freed track actual bytes of allocations, rather
than user sizes?

And make overhead track the exact or estimated difference between the actual
allocations and user sizes, or be zero if unsupported?

This would at least be consistent across all platforms.

The cases:

1. You can know the user size and the allocation size. Do exact math.
2. You can know the user size and can't know the allocation size. Consistently
estimate on alloc/free using the known user size, and have overhead be an
estimate.
3. You can't know the user size, but can know the allocation size. Set overhead
size to 0.

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

So the problem here is that on other platforms malloc_usable_size() is terribly
inconsistent. I don't remember the full details but I remember somebody
reporting it to return just zero in lot of implementation (I think in Android).
Which is the reason why in the heap profiler we keep track separately of the
size of allocations (see base/trace_event/heap_profiler_allocation_register.h)
together with other context stuff like stacktrace (when enabled) and such

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Yeah - I think this'll be platform dependent enough that maybe it's best to
implement it for Windows first, then refine it?

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Side-tracking of individual allocs is a no-go for performance for this I think.
Maybe the easiest thing to do is to expose a "feature flag probing" of some sort
on the AllocatorDispatch, and to simply fail initialization if the underlying
heap doesn't work?

+size_t GetAllocSize(void* ptr) {
+  if (ptr == nullptr)
+    return 0U;
+
+  HANDLE heap_handle = reinterpret_cast<HANDLE>(_get_heap_handle());
+  return ::HeapSize(heap_handle, 0, ptr);
+}
+
+size_t EstimateOverhead(size_t size) {

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

this is going to be very tricky on tcmalloc (Linux/CrOS) where the overhead
depends a lot on the thread patterns.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Yeah, it doesn't have to be very accurate though. Maybe the easiest thing to do
is to delegate this also to the AllocatorDispatch?

+// TODO(siggi): Less Windows specific!
+  const size_t kHeaderSize = 8;
+#if defined(ARCH_CPU_64_BITS)
+  const size_t kAllocationGranularity = 16;
+#else
+  const size_t kAllocationGranularity = 8;
+#endif
+  size_t overhead = 0;
+  if (size % kAllocationGranularity != 0)
+    overhead = kAllocationGranularity - (size % kAllocationGranularity);
+
+  // This is a lower-bound estimate on the Windows heap overhead.
+  return kHeaderSize + overhead;
+}
+
+void RecordAlloc(size_t size) {
+  ScopedHeapUsage::AllocatorUsage* usage = GetOrCreateThreadUsage();
+  if (usage == nullptr)
+    return;
+
+  usage->alloc_ops++;
+  usage->alloc_bytes += size;
+  usage->alloc_overhead_bytes += EstimateOverhead(size);
+
+  uint64_t allocated_bytes = usage->alloc_bytes - usage->free_bytes;
+  if (allocated_bytes > usage->max_allocated_bytes)
+    usage->max_allocated_bytes = allocated_bytes;
+}
+
+void RecordFree(size_t size) {
+  ScopedHeapUsage::AllocatorUsage* usage = GetOrCreateThreadUsage();
+  if (usage == nullptr)
+    return;
+
+  usage->free_ops++;
+  usage->free_bytes += size;
+}
+
+void* AllocFn(const AllocatorDispatch* self, size_t size) {
+  void* ret = self->next->alloc_function(self, size);
+  if (ret != nullptr)
+    RecordAlloc(size);
+
+  return ret;
+}
+
+void* AllocZeroInitializedFn(const AllocatorDispatch* self,
+                             size_t n,
+                             size_t size) {
+  void* ret = self->next->alloc_zero_initialized_function(self, n, size);
+  if (ret != nullptr)
+    RecordAlloc(n * size);
+
+  return ret;
+}
+
+void* AllocAlignedFn(const AllocatorDispatch* self,
+                     size_t alignment,
+                     size_t size) {
+  void* ret = self->next->alloc_aligned_function(self, alignment, size);
+  if (ret != nullptr)
+    RecordAlloc(size);
+
+  return ret;
+}
+
+void* ReallocFn(const AllocatorDispatch* self, void* address, size_t size) {
+  if (address != nullptr)
+    RecordFree(GetAllocSize(address));
+
+  void* ret = self->next->realloc_function(self, address, size);
+  if (ret != nullptr)
+    RecordAlloc(size);
+
+  return ret;
+}
+
+void FreeFn(const AllocatorDispatch* self, void* address) {
+  size_t alloc_size = GetAllocSize(address);
+  self->next->free_function(self, address);
+  RecordFree(alloc_size);
+}
+
+// The dispatch for the heap interept used.
+AllocatorDispatch allocator_dispatch = {
+    &AllocFn, &AllocZeroInitializedFn, &AllocAlignedFn, &ReallocFn, &FreeFn,
+    nullptr};
+
+ScopedHeapUsage::AllocatorUsage* GetOrCreateThreadUsage() {
+  using AllocatorUsage = ScopedHeapUsage::AllocatorUsage;
+
+  base::ThreadLocalPointer<AllocatorUsage>& usage_tls =
+      g_thread_allocator_usage.Get();

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

Isn't this going to re-enter (either the lazy instance or the tls, very likely
both)?
I had some similar problems in
base/trace_event/heap_profiler_allocation_context_tracker.cc you can take a look
there for inspiration.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

I haven't seen it reenter, but obviously I haven't tried other platforms. I
appropriated^Wadopted your implementation for TLS - thanks.

+
+  AllocatorUsage* usage = usage_tls.Get();
+  if (usage == nullptr) {
+    CHECK(allocator_dispatch.next != nullptr);

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

no need for this check, if this is null will crash 2 lines below anyways

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Acknowledged.

+
+    // Delegate the memory allocation to the next lower heap shim to avoid
+    // infinite recursion.
+    const AllocatorDispatch* next = allocator_dispatch.next;
+    usage = reinterpret_cast<AllocatorUsage*>(
+        next->alloc_function(next, sizeof(AllocatorUsage)));

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

you could just use alloc_zero_initialized_function to avoid the memset below.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

+    memset(usage, 0, sizeof(AllocatorUsage));
+    usage_tls.Set(usage);

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

so the problem here is that you are leaking one "usage" instace per thread.
Which means that if something is creating and destroy threads you'll keep
leaking this.

In heap_profiler_allocation_context_tracker.cc  I used
ThreadLocalStorage::StaticSlot which allows to specify a thread-exit dtor for
the object.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

+  }
+
+  return usage;
+}
+
+}  // namespace
+
+ScopedHeapUsage::ScopedHeapUsage() : thread_usage_(GetOrCreateThreadUsage()) {
+  if (thread_usage_ != nullptr) {
+    usage_at_creation_ = *thread_usage_;
+    // Reset the max allocation tally for this scope.
+    thread_usage_->max_allocated_bytes = 0U;
+  } else {

[chrisha, 2016/07/21 14:23:31]

Shouldn't thread_usage_ always be non-null at this point? Guaranteed by
GetOrCreateThreadUsage?

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

+1

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

+    // TODO(siggi): Is this even a good idea?
+    usage_at_creation_ = AllocatorUsage();
+  }
+}
+
+ScopedHeapUsage::~ScopedHeapUsage() {
+  if (thread_usage_ != nullptr &&
+      usage_at_creation_.max_allocated_bytes >
+          thread_usage_->max_allocated_bytes) {
+    // Restore the outer scope's max allocation tally, as it's larger than
+    // our scope's max.

[chrisha, 2016/07/21 14:23:30]

This mechanism requires that scopes be properly nested, without overlap. Worth
documenting somewhere?

(Admittedly you'd have to go through various contortions to have this happen,
but worth stating maybe?)

[Primiano Tucci (use gerrit), 2016/07/21 15:59:20]

maybe you can have a global Atomic32 g_scoped_heap_usage_enabled and a DCHECK to
prevent overlapping usages?

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

I'd prefer to just document this problem away, but another way to go would be to
maintain the "current" scope in the TLS data, and to barf hard if ever there's a
push/pop mismatch. This'd require the "prev" scope to be stored in the current
scope as well. I added a comment on the class declaration.

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Acknowledged.

+    thread_usage_->max_allocated_bytes = usage_at_creation_.max_allocated_bytes;
+  }
+}
+
+ScopedHeapUsage::AllocatorUsage ScopedHeapUsage::Now() {
+  AllocatorUsage* usage = GetOrCreateThreadUsage();
+  if (usage == nullptr)

[chrisha, 2016/07/21 14:23:30]

Can this even be null?

[Sigurður Ásgeirsson, 2016/08/19 18:21:49]

Done.

+    return AllocatorUsage();
+
+  return *usage;
+}
+
+void ScopedHeapUsage::Initialize() {
+  InsertAllocatorDispatch(&allocator_dispatch);
+}
+
+void ScopedHeapUsage::TearDownForTesting() {
+  RemoveAllocatorDispatchForTesting(&allocator_dispatch);
+}
+
+}  // namespace debug
+}  // namespace base