commit bd4655485351901cd972606abb72d5d35f7aea39
author wub <wub@google.com> Fri Mar 06 13:33:54 2020 -0800
committer Copybara-Service <copybara-worker@google.com> Fri Mar 06 13:34:24 2020 -0800
tree 145b5d9f4948ca84952f28c308e39412fbeca0bc
parent a66f68433ddd57305e5c116101d4cd59091bed37

gfe-relnote: In QUIC BBRv2, add ack height into PROBE_UP's queuing_threshold. Protected by --gfe2_reloadable_flag_quic_bbr2_add_ack_height_to_queueing_threshold.

PiperOrigin-RevId: 299425371
Change-Id: I8643b5df6bb72f0759695f31e6f480a1bc4d3400

quic/core/congestion_control/bbr2_probe_bw.cc

diff --git a/quic/core/congestion_control/bbr2_probe_bw.cc b/quic/core/congestion_control/bbr2_probe_bw.cc
index a4c419a..1002983 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.cc
+++ b/quic/core/congestion_control/bbr2_probe_bw.cc
@@ -391,9 +391,16 @@
     // TCP uses min_rtt instead of a full round:
     //   HasPhaseLasted(model_->MinRtt(), congestion_event)
   } else if (cycle_.rounds_in_phase > 0) {
-    QuicByteCount bdp = model_->BDP(model_->MaxBandwidth());
+    const QuicByteCount bdp = model_->BDP(model_->MaxBandwidth());
+    QuicByteCount queuing_threshold_extra_bytes = 2 * kDefaultTCPMSS;
+    if (add_ack_height_to_queueing_threshold_) {
+      QUIC_RELOADABLE_FLAG_COUNT(
+          quic_bbr2_add_ack_height_to_queueing_threshold);
+      queuing_threshold_extra_bytes += model_->MaxAckHeight();
+    }
     QuicByteCount queuing_threshold =
-        (Params().probe_bw_probe_inflight_gain * bdp) + 2 * kDefaultTCPMSS;
+        (Params().probe_bw_probe_inflight_gain * bdp) +
+        queuing_threshold_extra_bytes;
     is_queuing = prior_in_flight >= queuing_threshold;
     QUIC_DVLOG(3) << sender_
                   << " Checking if building up a queue. prior_in_flight:"

quic/core/congestion_control/bbr2_probe_bw.h

diff --git a/quic/core/congestion_control/bbr2_probe_bw.h b/quic/core/congestion_control/bbr2_probe_bw.h
index 5c0224f..e42ab30 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.h
+++ b/quic/core/congestion_control/bbr2_probe_bw.h
@@ -126,6 +126,9 @@
 
   bool last_cycle_probed_too_high_;
   bool last_cycle_stopped_risky_probe_;
+
+  const bool add_ack_height_to_queueing_threshold_ =
+      GetQuicReloadableFlag(quic_bbr2_add_ack_height_to_queueing_threshold);
 };
 
 QUIC_EXPORT_PRIVATE std::ostream& operator<<(

quic/core/congestion_control/bbr2_simulator_test.cc

diff --git a/quic/core/congestion_control/bbr2_simulator_test.cc b/quic/core/congestion_control/bbr2_simulator_test.cc
index e3af3dc..553dfcf 100644
--- a/quic/core/congestion_control/bbr2_simulator_test.cc
+++ b/quic/core/congestion_control/bbr2_simulator_test.cc
@@ -409,7 +409,7 @@
 
   // The margin here is quite high, since there exists a possibility that the
   // connection just exited high gain cycle.
-  EXPECT_APPROX_EQ(params.RTT(), rtt_stats()->smoothed_rtt(), 0.2f);
+  EXPECT_APPROX_EQ(params.RTT(), rtt_stats()->smoothed_rtt(), 1.0f);
 }
 
 TEST_F(Bbr2DefaultTopologyTest, SimpleTransferSmallBuffer) {
@@ -487,7 +487,7 @@
   EXPECT_FALSE(sender_->ExportDebugState().last_sample_is_app_limited);
   // The margin here is high, because the aggregation greatly increases
   // smoothed rtt.
-  EXPECT_GE(params.RTT() * 2, rtt_stats()->smoothed_rtt());
+  EXPECT_GE(params.RTT() * 3, rtt_stats()->smoothed_rtt());
   EXPECT_APPROX_EQ(params.RTT(), rtt_stats()->min_rtt(), 0.1f);
 }