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1 /*
2  *
3  * Copyright 2016 gRPC authors.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  *
17  */
18 
19 #include <grpc/support/port_platform.h>
20 
21 #include "src/core/lib/transport/bdp_estimator.h"
22 
23 #include <inttypes.h>
24 #include <stdlib.h>
25 
26 #include "src/core/lib/gpr/useful.h"
27 
28 grpc_core::TraceFlag grpc_bdp_estimator_trace(false, "bdp_estimator");
29 
30 namespace grpc_core {
31 
BdpEstimator(const char * name)32 BdpEstimator::BdpEstimator(const char* name)
33     : ping_state_(PingState::UNSCHEDULED),
34       accumulator_(0),
35       estimate_(65536),
36       ping_start_time_(gpr_time_0(GPR_CLOCK_MONOTONIC)),
37       inter_ping_delay_(100.0),  // start at 100ms
38       stable_estimate_count_(0),
39       bw_est_(0),
40       name_(name) {}
41 
CompletePing()42 grpc_millis BdpEstimator::CompletePing() {
43   gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
44   gpr_timespec dt_ts = gpr_time_sub(now, ping_start_time_);
45   double dt = static_cast<double>(dt_ts.tv_sec) +
46               1e-9 * static_cast<double>(dt_ts.tv_nsec);
47   double bw = dt > 0 ? (static_cast<double>(accumulator_) / dt) : 0;
48   int start_inter_ping_delay = inter_ping_delay_;
49   if (grpc_bdp_estimator_trace.enabled()) {
50     gpr_log(GPR_INFO,
51             "bdp[%s]:complete acc=%" PRId64 " est=%" PRId64
52             " dt=%lf bw=%lfMbs bw_est=%lfMbs",
53             name_, accumulator_, estimate_, dt, bw / 125000.0,
54             bw_est_ / 125000.0);
55   }
56   GPR_ASSERT(ping_state_ == PingState::STARTED);
57   if (accumulator_ > 2 * estimate_ / 3 && bw > bw_est_) {
58     estimate_ = GPR_MAX(accumulator_, estimate_ * 2);
59     bw_est_ = bw;
60     if (grpc_bdp_estimator_trace.enabled()) {
61       gpr_log(GPR_INFO, "bdp[%s]: estimate increased to %" PRId64, name_,
62               estimate_);
63     }
64     inter_ping_delay_ /= 2;  // if the ping estimate changes,
65                              // exponentially get faster at probing
66   } else if (inter_ping_delay_ < 10000) {
67     stable_estimate_count_++;
68     if (stable_estimate_count_ >= 2) {
69       inter_ping_delay_ +=
70           100 + static_cast<int>(rand() * 100.0 /
71                                  RAND_MAX);  // if the ping estimate is steady,
72                                              // slowly ramp down the probe time
73     }
74   }
75   if (start_inter_ping_delay != inter_ping_delay_) {
76     stable_estimate_count_ = 0;
77     if (grpc_bdp_estimator_trace.enabled()) {
78       gpr_log(GPR_INFO, "bdp[%s]:update_inter_time to %dms", name_,
79               inter_ping_delay_);
80     }
81   }
82   ping_state_ = PingState::UNSCHEDULED;
83   accumulator_ = 0;
84   return grpc_core::ExecCtx::Get()->Now() + inter_ping_delay_;
85 }
86 
87 }  // namespace grpc_core
88