src: add tracing.v8.on('gc') statistics hooks

Add a new 'tracing' module with a v8 property that lets the user
register listeners for gc events.  The listeners are invoked after
every garbage collection cycle with 'before' and 'after' statistics.
Useful for monitoring tools that want to keep track of memory usage.

1 files changed, 200 insertions, 0 deletions

diff --git a/src/node_v8.cc b/src/node_v8.cc
new file mode 100644
index 00000000000..2fd276342d1
--- /dev/null
+++ b/src/node_v8.cc
@@ -0,0 +1,200 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+#include "node.h"
+#include "env.h"
+#include "env-inl.h"
+#include "util.h"
+#include "util-inl.h"
+#include "v8.h"
+
+namespace node {
+
+using v8::Context;
+using v8::Function;
+using v8::FunctionCallbackInfo;
+using v8::GCCallbackFlags;
+using v8::GCType;
+using v8::Handle;
+using v8::HandleScope;
+using v8::Isolate;
+using v8::Local;
+using v8::Null;
+using v8::Number;
+using v8::Object;
+using v8::Uint32;
+using v8::Value;
+using v8::kGCTypeAll;
+using v8::kGCTypeMarkSweepCompact;
+using v8::kGCTypeScavenge;
+
+
+void Environment::IsolateData::BeforeGarbageCollection(Isolate* isolate,
+                                                       GCType type,
+                                                       GCCallbackFlags flags) {
+  Get(isolate)->BeforeGarbageCollection(type, flags);
+}
+
+
+void Environment::IsolateData::AfterGarbageCollection(Isolate* isolate,
+                                                      GCType type,
+                                                      GCCallbackFlags flags) {
+  Get(isolate)->AfterGarbageCollection(type, flags);
+}
+
+
+void Environment::IsolateData::BeforeGarbageCollection(GCType type,
+                                                       GCCallbackFlags flags) {
+  gc_info_before_ = GCInfo(isolate(), type, flags, uv_hrtime());
+}
+
+
+void Environment::IsolateData::AfterGarbageCollection(GCType type,
+                                                      GCCallbackFlags flags) {
+  gc_info_after_ = GCInfo(isolate(), type, flags, uv_hrtime());
+
+  // The copy upfront and the remove-then-insert is to avoid corrupting the
+  // list when the callback removes itself from it.  QUEUE_FOREACH() is unsafe
+  // when the list is mutated while being walked.
+  ASSERT(QUEUE_EMPTY(&gc_tracker_queue_) == false);
+  QUEUE queue;
+  QUEUE* q = QUEUE_HEAD(&gc_tracker_queue_);
+  QUEUE_SPLIT(&gc_tracker_queue_, q, &queue);
+  while (QUEUE_EMPTY(&queue) == false) {
+    q = QUEUE_HEAD(&queue);
+    QUEUE_REMOVE(q);
+    QUEUE_INSERT_TAIL(&gc_tracker_queue_, q);
+    Environment* env = CONTAINER_OF(q, Environment, gc_tracker_queue_);
+    env->AfterGarbageCollectionCallback(&gc_info_before_, &gc_info_after_);
+  }
+}
+
+
+void Environment::IsolateData::StartGarbageCollectionTracking(
+    Environment* env) {
+  if (QUEUE_EMPTY(&gc_tracker_queue_)) {
+    isolate()->AddGCPrologueCallback(BeforeGarbageCollection, v8::kGCTypeAll);
+    isolate()->AddGCEpilogueCallback(AfterGarbageCollection, v8::kGCTypeAll);
+  }
+  ASSERT(QUEUE_EMPTY(&env->gc_tracker_queue_) == true);
+  QUEUE_INSERT_TAIL(&gc_tracker_queue_, &env->gc_tracker_queue_);
+}
+
+
+void Environment::IsolateData::StopGarbageCollectionTracking(Environment* env) {
+  ASSERT(QUEUE_EMPTY(&env->gc_tracker_queue_) == false);
+  QUEUE_REMOVE(&env->gc_tracker_queue_);
+  QUEUE_INIT(&env->gc_tracker_queue_);
+  if (QUEUE_EMPTY(&gc_tracker_queue_)) {
+    isolate()->RemoveGCPrologueCallback(BeforeGarbageCollection);
+    isolate()->RemoveGCEpilogueCallback(AfterGarbageCollection);
+  }
+}
+
+
+// Considering a memory constrained environment, creating more objects is less
+// than ideal
+void Environment::AfterGarbageCollectionCallback(const GCInfo* before,
+                                                 const GCInfo* after) {
+  HandleScope handle_scope(isolate());
+  Context::Scope context_scope(context());
+  Local<Value> argv[] = { Object::New(), Object::New() };
+  const GCInfo* infov[] = { before, after };
+  for (unsigned i = 0; i < ARRAY_SIZE(argv); i += 1) {
+    Local<Object> obj = argv[i].As<Object>();
+    const GCInfo* info = infov[i];
+    switch (info->type()) {
+      case kGCTypeScavenge:
+        obj->Set(type_string(), scavenge_string());
+        break;
+      case kGCTypeMarkSweepCompact:
+        obj->Set(type_string(), mark_sweep_compact_string());
+        break;
+      default:
+        UNREACHABLE();
+    }
+    obj->Set(flags_string(), Uint32::NewFromUnsigned(info->flags(), isolate()));
+    obj->Set(timestamp_string(), Number::New(isolate(), info->timestamp()));
+    // TODO(trevnorris): Setting many object properties in C++ is a significant
+    // performance hit. Redo this to pass the results to JS and create/set the
+    // properties there.
+#define V(name)                                                               \
+    do {                                                                      \
+      obj->Set(name ## _string(),                                             \
+               Uint32::NewFromUnsigned(info->stats()->name(), isolate()));    \
+    } while (0)
+    V(total_heap_size);
+    V(total_heap_size_executable);
+    V(total_physical_size);
+    V(used_heap_size);
+    V(heap_size_limit);
+#undef V
+  }
+  MakeCallback(this,
+               Null(isolate()),
+               gc_info_callback_function(),
+               ARRAY_SIZE(argv),
+               argv);
+}
+
+
+void Environment::StartGarbageCollectionTracking(Local<Function> callback) {
+  ASSERT(gc_info_callback_function().IsEmpty() == true);
+  set_gc_info_callback_function(callback);
+  isolate_data()->StartGarbageCollectionTracking(this);
+}
+
+
+void Environment::StopGarbageCollectionTracking() {
+  ASSERT(gc_info_callback_function().IsEmpty() == false);
+  isolate_data()->StopGarbageCollectionTracking(this);
+  set_gc_info_callback_function(Local<Function>());
+}
+
+
+void StartGarbageCollectionTracking(const FunctionCallbackInfo<Value>& args) {
+  CHECK(args[0]->IsFunction() == true);
+  HandleScope handle_scope(args.GetIsolate());
+  Environment* env = Environment::GetCurrent(args.GetIsolate());
+  env->StartGarbageCollectionTracking(args[0].As<Function>());
+}
+
+
+void StopGarbageCollectionTracking(const FunctionCallbackInfo<Value>& args) {
+  HandleScope handle_scope(args.GetIsolate());
+  Environment::GetCurrent(args.GetIsolate())->StopGarbageCollectionTracking();
+}
+
+
+void InitializeV8Bindings(Handle<Object> target,
+                          Handle<Value> unused,
+                          Handle<Context> context) {
+  NODE_SET_METHOD(target,
+                  "startGarbageCollectionTracking",
+                  StartGarbageCollectionTracking);
+  NODE_SET_METHOD(target,
+                  "stopGarbageCollectionTracking",
+                  StopGarbageCollectionTracking);
+}
+
+}  // namespace node
+
+NODE_MODULE_CONTEXT_AWARE_BUILTIN(v8, node::InitializeV8Bindings)