commit c2fd610bd20101eeb35a1e495e3fed0ac256b0b9
author fayang <fayang@google.com> Mon Mar 02 17:27:38 2020 -0800
committer Copybara-Service <copybara-worker@google.com> Mon Mar 02 17:28:16 2020 -0800
tree 866f721adc766a718d5d68bddf0ad7fed2227f3b
parent 7e5e609bc7a1f355471497fdd0d63b3025de2350

gfe-relnote: In QUIC, use standard deviation to calculate PTO timeout. Protected by gfe2_reloadable_flag_quic_use_standard_deviation_for_pto.

PiperOrigin-RevId: 298487425
Change-Id: Ie29e4226796af161a9a5b777cd59486ea5cb5d3d

quic/core/quic_sent_packet_manager.cc

diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index b6eae54..c8fd641 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -106,7 +106,8 @@
       num_tlp_timeout_ptos_(0),
       one_rtt_packet_acked_(false),
       one_rtt_packet_sent_(false),
-      first_pto_srtt_multiplier_(0) {
+      first_pto_srtt_multiplier_(0),
+      use_standard_deviation_for_pto_(false) {
   SetSendAlgorithm(congestion_control_type);
 }
 
@@ -198,6 +199,12 @@
         first_pto_srtt_multiplier_ = 1.5;
       }
     }
+    if (GetQuicReloadableFlag(quic_use_standard_deviation_for_pto) &&
+        config.HasClientSentConnectionOption(kPSDA, perspective)) {
+      QUIC_RELOADABLE_FLAG_COUNT(quic_use_standard_deviation_for_pto);
+      use_standard_deviation_for_pto_ = true;
+      rtt_stats_.EnableStandardDeviationCalculation();
+    }
   }
 
   // Configure congestion control.
@@ -1143,10 +1150,12 @@
     }
     return 2 * rtt_stats_.initial_rtt();
   }
+  const QuicTime::Delta rtt_var = use_standard_deviation_for_pto_
+                                      ? rtt_stats_.GetStandardOrMeanDeviation()
+                                      : rtt_stats_.mean_deviation();
   QuicTime::Delta pto_delay =
       rtt_stats_.smoothed_rtt() +
-      std::max(pto_rttvar_multiplier_ * rtt_stats_.mean_deviation(),
-               kAlarmGranularity) +
+      std::max(pto_rttvar_multiplier_ * rtt_var, kAlarmGranularity) +
       (ShouldAddMaxAckDelay() ? peer_max_ack_delay_ : QuicTime::Delta::Zero());
   pto_delay =
       pto_delay * (1 << (consecutive_pto_count_ -