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 "src/core/lib/transport/bdp_estimator.h"
20
21 #include <grpc/support/port_platform.h>
22 #include <inttypes.h>
23 #include <stdlib.h>
24
25 #include <algorithm>
26
27 #include "absl/log/check.h"
28 #include "absl/log/log.h"
29
30 namespace grpc_core {
31
BdpEstimator(absl::string_view name)32 BdpEstimator::BdpEstimator(absl::string_view name)
33 : accumulator_(0),
34 estimate_(65536),
35 ping_start_time_(gpr_time_0(GPR_CLOCK_MONOTONIC)),
36 inter_ping_delay_(Duration::Milliseconds(100)), // start at 100ms
37 stable_estimate_count_(0),
38 ping_state_(PingState::UNSCHEDULED),
39 bw_est_(0),
40 name_(name) {}
41
CompletePing()42 Timestamp 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 Duration start_inter_ping_delay = inter_ping_delay_;
49 GRPC_TRACE_LOG(bdp_estimator, INFO)
50 << "bdp[" << name_ << "]:complete acc=" << accumulator_
51 << " est=" << estimate_ << " dt=" << dt << " bw=" << bw / 125000.0
52 << "Mbs bw_est=" << bw_est_ / 125000.0 << "Mbs";
53 CHECK(ping_state_ == PingState::STARTED);
54 if (accumulator_ > 2 * estimate_ / 3 && bw > bw_est_) {
55 estimate_ = std::max(accumulator_, estimate_ * 2);
56 bw_est_ = bw;
57 GRPC_TRACE_LOG(bdp_estimator, INFO)
58 << "bdp[" << name_ << "]: estimate increased to " << estimate_;
59 inter_ping_delay_ /= 2; // if the ping estimate changes,
60 // exponentially get faster at probing
61 } else if (inter_ping_delay_ < Duration::Seconds(10)) {
62 stable_estimate_count_++;
63 if (stable_estimate_count_ >= 2) {
64 // if the ping estimate is steady, slowly ramp down the probe time
65 inter_ping_delay_ += Duration::Milliseconds(
66 100 + static_cast<int>(rand() * 100.0 / RAND_MAX));
67 }
68 }
69 if (start_inter_ping_delay != inter_ping_delay_) {
70 stable_estimate_count_ = 0;
71 GRPC_TRACE_LOG(bdp_estimator, INFO)
72 << "bdp[" << name_ << "]:update_inter_time to "
73 << inter_ping_delay_.millis() << "ms";
74 }
75 ping_state_ = PingState::UNSCHEDULED;
76 accumulator_ = 0;
77 return Timestamp::Now() + inter_ping_delay_;
78 }
79
80 } // namespace grpc_core
81