Backed out changeset 686ae9e71a9c (bug 1631402) for causing build bustage in MessageChannel.cpp

ipc/chromium/src/base/pickle.cc

@@ -86,7 +86,7 @@ struct Copier<T, size, true> {
 }  // anonymous namespace
 
 PickleIterator::PickleIterator(const Pickle& pickle)
-    : iter_(pickle.buffers_.Iter()) {
+    : iter_(pickle.buffers_.Iter()), start_(mozilla::TimeStamp::Now()) {
   iter_.Advance(pickle.buffers_, pickle.header_size_);
 }
 
@@ -458,6 +458,17 @@ bool Pickle::WriteSentinel(uint32_t sentinel) { return WriteUInt32(sentinel); }
 void Pickle::EndRead(PickleIterator& iter, uint32_t ipcMsgType) const {
   // FIXME: Deal with the footer somehow...
   // DCHECK(iter.iter_.Done());
+
+  if (NS_IsMainThread() && ipcMsgType != 0) {
+    uint32_t latencyMs =
+        round((mozilla::TimeStamp::Now() - iter.start_).ToMilliseconds());
+    if (latencyMs >= kMinTelemetryIPCReadLatencyMs) {
+      mozilla::Telemetry::Accumulate(
+          mozilla::Telemetry::IPC_READ_MAIN_THREAD_LATENCY_MS,
+          nsDependentCString(IPC::StringFromIPCMessageType(ipcMsgType)),
+          latencyMs);
+    }
+  }
 }
 
 void Pickle::Truncate(PickleIterator* iter) {

ipc/chromium/src/base/pickle.h

@@ -32,6 +32,7 @@ class PickleIterator {
   friend class Pickle;
 
   mozilla::BufferList<InfallibleAllocPolicy>::IterImpl iter_;
+  mozilla::TimeStamp start_;
 
   template <typename T>
   void CopyInto(T* dest);

ipc/chromium/src/chrome/common/ipc_message.cc

@@ -30,7 +30,7 @@ Message::Message()
 }
 
 Message::Message(int32_t routing_id, msgid_t type, uint32_t segment_capacity,
-                 HeaderFlags flags)
+                 HeaderFlags flags, bool recordWriteLatency)
     : UserMessage(&kUserMessageTypeInfo),
       Pickle(sizeof(Header), segment_capacity) {
   MOZ_COUNT_CTOR(IPC::Message);
@@ -46,6 +46,9 @@ Message::Message(int32_t routing_id, msgid_t type, uint32_t segment_capacity,
   header()->num_send_rights = 0;
 #endif
   header()->event_footer_size = 0;
+  if (recordWriteLatency) {
+    create_time_ = mozilla::TimeStamp::Now();
+  }
 }
 
 Message::Message(const char* data, int data_len)
@@ -69,7 +72,7 @@ Message::Message(Message&& other)
 
 /*static*/ Message* Message::IPDLMessage(int32_t routing_id, msgid_t type,
                                          HeaderFlags flags) {
-  return new Message(routing_id, type, 0, flags);
+  return new Message(routing_id, type, 0, flags, true);
 }
 
 /*static*/ Message* Message::ForSyncDispatchError(NestedLevel level) {

ipc/chromium/src/chrome/common/ipc_message.h

@@ -171,9 +171,12 @@ class Message : public mojo::core::ports::UserMessage, public Pickle {
 
   // Initialize a message with a user-defined type, priority value, and
   // destination WebView ID.
+  //
+  // NOTE: `recordWriteLatency` is only passed by IPDL generated message code,
+  // and is used to trigger the IPC_WRITE_LATENCY_MS telemetry.
   Message(int32_t routing_id, msgid_t type,
           uint32_t segmentCapacity = 0,  // 0 for the default capacity.
-          HeaderFlags flags = HeaderFlags());
+          HeaderFlags flags = HeaderFlags(), bool recordWriteLatency = false);
 
   Message(const char* data, int data_len);
 
@@ -249,6 +252,8 @@ class Message : public mojo::core::ports::UserMessage, public Pickle {
 
   const char* name() const { return StringFromIPCMessageType(type()); }
 
+  const mozilla::TimeStamp& create_time() const { return create_time_; }
+
   uint32_t num_handles() const;
 
   bool is_relay() const { return header()->flags.IsRelay(); }
@@ -426,6 +431,8 @@ class Message : public mojo::core::ports::UserMessage, public Pickle {
   // deserializing a message.
   mutable nsTArray<mozilla::UniqueMachSendRight> attached_send_rights_;
 #endif
+
+  mozilla::TimeStamp create_time_;
 };
 
 class MessageInfo {

ipc/glue/MessageChannel.cpp

@@ -853,6 +853,20 @@ bool MessageChannel::Send(UniquePtr<Message> aMsg) {
     Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE2, aMsg->size());
   }
 
+  // If the message was created by the IPC bindings, the create time will be
+  // recorded. Use this information to report the
+  // IPC_WRITE_MAIN_THREAD_LATENCY_MS (time from message creation to it being
+  // sent).
+  if (NS_IsMainThread() && aMsg->create_time()) {
+    uint32_t latencyMs = round(
+        (mozilla::TimeStamp::Now() - aMsg->create_time()).ToMilliseconds());
+    if (latencyMs >= kMinTelemetryIPCWriteLatencyMs) {
+      mozilla::Telemetry::Accumulate(
+          mozilla::Telemetry::IPC_WRITE_MAIN_THREAD_LATENCY_MS,
+          nsDependentCString(aMsg->name()), latencyMs);
+    }
+  }
+
   MOZ_RELEASE_ASSERT(!aMsg->is_sync());
   MOZ_RELEASE_ASSERT(aMsg->nested_level() != IPC::Message::NESTED_INSIDE_SYNC);
 

ipc/ipdl/ipdl/lower.py

@@ -1943,6 +1943,8 @@ def _generateMessageConstructor(md, segmentSize, protocol, forReply=False):
                         ExprVar(msgid),
                         ExprLiteral.Int(int(segmentSize)),
                         flags,
+                        # Pass `true` to recordWriteLatency to collect telemetry
+                        ExprLiteral.TRUE,
                     ],
                 )
             )

toolkit/components/telemetry/Histograms.json

@@ -15146,6 +15146,30 @@
     "description": "Results of displaying add-on installation notifications.",
     "releaseChannelCollection": "opt-out"
   },
+  "IPC_READ_MAIN_THREAD_LATENCY_MS": {
+    "record_in_processes": ["main", "content", "gpu"],
+    "products": ["firefox", "fennec"],
+    "alert_emails": ["mlayzell@mozilla.com"],
+    "bug_numbers": [1342635],
+    "expires_in_version": "60",
+    "kind": "exponential",
+    "high": 500,
+    "n_buckets": 20,
+    "keyed": true,
+    "description": "Measures the number of milliseconds we spend waiting on the main thread for IPC messages to deserialize their parameters. Note: only messages that take more than 500 microseconds are included in this probe. This probe is keyed on the IPDL message name."
+  },
+  "IPC_WRITE_MAIN_THREAD_LATENCY_MS": {
+    "record_in_processes": ["main", "content", "gpu"],
+    "products": ["firefox", "fennec"],
+    "alert_emails": ["mlayzell@mozilla.com"],
+    "bug_numbers": [1342635],
+    "expires_in_version": "60",
+    "kind": "exponential",
+    "high": 500,
+    "n_buckets": 20,
+    "keyed": true,
+    "description": "Measures the number of milliseconds we spend waiting on the main thread for IPC messages to serialize their parameters. Note: only messages that take more than 500 microseconds are included in this probe. This probe is keyed on the IPDL message name."
+  },
   "INPUT_EVENT_QUEUED_CLICK_MS": {
     "record_in_processes": ["main", "content"],
     "products": ["firefox", "fennec"],