Remove unused histograms: Net.QuicSession.21* & Net.QuicSession.6*

net/quic/quic_connection_logger.cc

Index: net/quic/quic_connection_logger.cc
diff --git a/net/quic/quic_connection_logger.cc b/net/quic/quic_connection_logger.cc
index b9cb00e322321d88847f6020af70795935d78201..427e1a4e97a08a72737458ab86a9f711ff9508da 100644
--- a/net/quic/quic_connection_logger.cc
+++ b/net/quic/quic_connection_logger.cc
@@ -33,11 +33,6 @@ namespace net {
 
 namespace {
 
-// We have ranges-of-buckets in the cumulative histogram (covering 21 packet
-// sequences) of length 2, 3, 4, ... 22.
-// Hence the largest sample is bounded by the sum of those numbers.
-const int kBoundingSampleInCumulativeHistogram = ((2 + 22) * 21) / 2;
-
 scoped_ptr<base::Value> NetLogQuicPacketCallback(
     const IPEndPoint* self_address,
     const IPEndPoint* peer_address,
@@ -709,60 +704,6 @@ base::HistogramBase* QuicConnectionLogger::GetPacketNumberHistogram(
       base::HistogramBase::kUmaTargetedHistogramFlag);
 }
 
-base::HistogramBase* QuicConnectionLogger::Get6PacketHistogram(
-    const char* which_6) const {
-  // This histogram takes a binary encoding of the 6 consecutive packets
-  // received.  As a result, there are 64 possible sample-patterns.
-  string prefix("Net.QuicSession.6PacketsPatternsReceived_");
-  return base::LinearHistogram::FactoryGet(
-      prefix + which_6 + connection_description_, 1, 64, 65,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-}
-
-base::HistogramBase* QuicConnectionLogger::Get21CumulativeHistogram(
-    const char* which_21) const {
-  // This histogram contains, for each sequence of 21 packets, the results from
-  // 21 distinct questions about that sequence.  Conceptually the histogtram is
-  // broken into 21 distinct ranges, and one sample is added into each of those
-  // ranges whenever we process a set of 21 packets.
-  // There is a little rendundancy, as each "range" must have the same number
-  // of samples, all told, but the histogram is a tad easier to read this way.
-  // The questions are:
-  // Was the first packet present (bucket 0==>no; bucket 1==>yes)
-  // Of the first two packets, how many were present? (bucket 2==> none;
-  //   bucket 3==> 1 of 2; bucket 4==> 2 of 2)
-  // Of the  first three packets, how many were present? (bucket 5==>none;
-  //   bucket 6==> 1 of 3; bucket 7==> 2 of 3; bucket 8==> 3 of 3).
-  // etc.
-  string prefix("Net.QuicSession.21CumulativePacketsReceived_");
-  return base::LinearHistogram::FactoryGet(
-      prefix + which_21 + connection_description_, 1,
-      kBoundingSampleInCumulativeHistogram,
-      kBoundingSampleInCumulativeHistogram + 1,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-}
-
-// static
-void QuicConnectionLogger::AddTo21CumulativeHistogram(
-    base::HistogramBase* histogram,
-    int bit_mask_of_packets,
-    int valid_bits_in_mask) {
-  DCHECK_LE(valid_bits_in_mask, 21);
-  DCHECK_LT(bit_mask_of_packets, 1 << 21);
-  const int blank_bits_in_mask = 21 - valid_bits_in_mask;
-  DCHECK_EQ(bit_mask_of_packets & ((1 << blank_bits_in_mask) - 1), 0);
-  bit_mask_of_packets >>= blank_bits_in_mask;
-  int bits_so_far = 0;
-  int range_start = 0;
-  for (int i = 1; i <= valid_bits_in_mask; ++i) {
-    bits_so_far += bit_mask_of_packets & 1;
-    bit_mask_of_packets >>= 1;
-    DCHECK_LT(range_start + bits_so_far, kBoundingSampleInCumulativeHistogram);
-    histogram->Add(range_start + bits_so_far);
-    range_start += i + 1;
-  }
-}
-
 float QuicConnectionLogger::ReceivedPacketLossRate() const {
   if (largest_received_packet_number_ <= num_packets_received_)
     return 0.0f;
@@ -813,17 +754,10 @@ void QuicConnectionLogger::RecordLossHistograms() const {
       GetPacketNumberHistogram("Ack_");
   base::HistogramBase* packet_missing_histogram =
       GetPacketNumberHistogram("Nack_");
-  base::HistogramBase* ongoing_cumulative_packet_histogram =
-      Get21CumulativeHistogram("Some21s_");
-  base::HistogramBase* first_cumulative_packet_histogram =
-      Get21CumulativeHistogram("First21_");
-  base::HistogramBase* six_packet_histogram = Get6PacketHistogram("Some6s_");
 
   DCHECK_EQ(received_packets_.size(), received_acks_.size());
   const QuicPacketNumber last_index = std::min<QuicPacketNumber>(
       received_packets_.size() - 1, largest_received_packet_number_);
-  const QuicPacketNumber index_of_first_21_contribution =
-      std::min<QuicPacketNumber>(21, last_index);
   // Bit pattern of consecutively received packets that is maintained as we scan
   // through the received_packets_ vector. Less significant bits correspond to
   // less recent packets, and only the low order 21 bits are ever defined.
@@ -845,29 +779,13 @@ void QuicConnectionLogger::RecordLossHistograms() const {
       packet_missing_histogram->Add(i);
     }
 
-    if (i == index_of_first_21_contribution) {
-      AddTo21CumulativeHistogram(first_cumulative_packet_histogram,
-                                 packet_pattern_21, i);
-    }
-    // We'll just record for non-overlapping ranges, to reduce histogramming
-    // cost for now.  Each call does 21 separate histogram additions.
-    if (i > 21 || i % 21 == 0) {
-      AddTo21CumulativeHistogram(ongoing_cumulative_packet_histogram,
-                                 packet_pattern_21, 21);
-    }
-
     if (i < 6)
       continue;  // Not enough packets to do any pattern recording.
     int recent_6_mask = packet_pattern_21 >> 15;
     DCHECK_LT(recent_6_mask, 64);
     if (i == 6) {
-      Get6PacketHistogram("First6_")->Add(recent_6_mask);
       continue;
     }
-    // Record some overlapping patterns, to get a better picture, since this is
-    // not very expensive.
-    if (i % 3 == 0)
-      six_packet_histogram->Add(recent_6_mask);
   }
 }