Implement UMA and internal data structure for tracking EWOULDBLOCK.

content/renderer/p2p/ipc_socket_factory.cc

Index: content/renderer/p2p/ipc_socket_factory.cc
diff --git a/content/renderer/p2p/ipc_socket_factory.cc b/content/renderer/p2p/ipc_socket_factory.cc
index 3dead8f5f0150362ddc69da33eee0aa0deff368c..3b2d1436ab07ad8a620978c84adc57903f13a3fa 100644
--- a/content/renderer/p2p/ipc_socket_factory.cc
+++ b/content/renderer/p2p/ipc_socket_factory.cc
@@ -11,6 +11,7 @@
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_loop_proxy.h"
+#include "base/metrics/histogram.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/non_thread_safe.h"
 #include "content/renderer/media/webrtc_logging.h"
@@ -114,6 +115,8 @@ class IpcPacketSocket : public rtc::AsyncPacketSocket,
     IS_ERROR,
   };
 
+  void IncrementDiscardCounters(uint32 size);

[Alexei Svitkine (slow), 2014/10/27 17:45:21]

This should have a comment. What is |size|?

[guoweis2, 2014/10/27 18:07:07]

Done.

+
   // Update trace of send throttling internal state. This should be called
   // immediately after any changes to |send_bytes_available_| and/or
   // |in_flight_packet_sizes_|.
@@ -161,6 +164,15 @@ class IpcPacketSocket : public rtc::AsyncPacketSocket,
   int error_;
   int options_[P2P_SOCKET_OPT_MAX];
 
+  // Track the maximum & current consecutive bytes discarded due to not enough
+  // send_bytes_available_.
+  uint32 max_discard_bytes_sequence_;
+  uint32 cur_discard_bytes_sequence_;
+
+  // Track total count of packet drops and attempt of packet sends.
+  uint32 packets_discarded_;
+  uint32 total_packets_;
+
   DISALLOW_COPY_AND_ASSIGN(IpcPacketSocket);
 };
 
@@ -195,7 +207,11 @@ IpcPacketSocket::IpcPacketSocket()
       state_(IS_UNINITIALIZED),
       send_bytes_available_(kMaximumInFlightBytes),
       writable_signal_expected_(false),
-      error_(0) {
+      error_(0),
+      max_discard_bytes_sequence_(0),
+      cur_discard_bytes_sequence_(0),
+      packets_discarded_(0),
+      total_packets_(0) {
   COMPILE_ASSERT(kMaximumInFlightBytes > 0, would_send_at_zero_rate);
   std::fill_n(options_, static_cast<int> (P2P_SOCKET_OPT_MAX),
               kDefaultNonSetOptionValue);
@@ -206,6 +222,15 @@ IpcPacketSocket::~IpcPacketSocket() {
       state_ == IS_ERROR) {
     Close();
   }
+
+  UMA_HISTOGRAM_COUNTS_10000("WebRTC.MaxApplicationConsecutiveBytesDiscard",
+                             max_discard_bytes_sequence_);
+
+  if (total_packets_ > 0) {
+    UMA_HISTOGRAM_PERCENTAGE("WebRTC.PacketDiscardByApplication",
+                             ((static_cast<double>(packets_discarded_)) /
+                              (static_cast<double>(total_packets_)) * 100.0));

[Alexei Svitkine (slow), 2014/10/27 17:45:21]

The usual way to do this is:

(packets_discarded_ * 100) / total_packets

The histogram value is an int anyway, so you don't need to do any double
conversion or division.

Same for the other histograms above where you log a percentage.

[guoweis2, 2014/10/27 18:07:07]

Done.

+  }
 }
 
 void IpcPacketSocket::TraceSendThrottlingState() const {
@@ -215,6 +240,15 @@ void IpcPacketSocket::TraceSendThrottlingState() const {
                     in_flight_packet_sizes_.size());
 }
 
+void IpcPacketSocket::IncrementDiscardCounters(uint32 size) {
+  cur_discard_bytes_sequence_ += size;
+  packets_discarded_++;
+
+  if (cur_discard_bytes_sequence_ > max_discard_bytes_sequence_) {
+    max_discard_bytes_sequence_ = cur_discard_bytes_sequence_;
+  }
+}
+
 bool IpcPacketSocket::Init(P2PSocketType type,
                            P2PSocketClientImpl* client,
                            const rtc::SocketAddress& local_address,
@@ -316,6 +350,8 @@ int IpcPacketSocket::SendTo(const void *data, size_t data_size,
     return 0;
   }
 
+  total_packets_++;
+
   if (data_size > send_bytes_available_) {
     TRACE_EVENT_INSTANT1("p2p", "MaxPendingBytesWouldBlock",
                          TRACE_EVENT_SCOPE_THREAD,
@@ -330,7 +366,10 @@ int IpcPacketSocket::SendTo(const void *data, size_t data_size,
     }
 
     error_ = EWOULDBLOCK;
+    IncrementDiscardCounters(data_size);
     return -1;
+  } else {
+    cur_discard_bytes_sequence_ = 0;
   }
 
   net::IPEndPoint address_chrome;