Keep track of the capacity delay error in the FakeNetworkPipe.
The FakeNetworkPipe use millisecond precision to calculate the delay induced by
the size of the packet being sent. The problem is that it rounds the delay down
to the closest millisecond which can cause a significant error in the actual
throughput. We keep track of that error to compensate the delay cause by
subsequent packets.
BUG=None
Review-Url: https://codereview.webrtc.org/3010653002
Cr-Original-Commit-Position: refs/heads/master@{#19732}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 19f51434e84589a8065fb9b20f059ff6b52dd853
diff --git a/test/fake_network_pipe.cc b/test/fake_network_pipe.cc
index bb9d6b1..61ac918 100644
--- a/test/fake_network_pipe.cc
+++ b/test/fake_network_pipe.cc
@@ -132,8 +132,16 @@
// Delay introduced by the link capacity.
int64_t capacity_delay_ms = 0;
- if (config_.link_capacity_kbps > 0)
- capacity_delay_ms = data_length / (config_.link_capacity_kbps / 8);
+ if (config_.link_capacity_kbps > 0) {
+ const int bytes_per_millisecond = config_.link_capacity_kbps / 8;
+ // To round to the closest millisecond we add half a milliseconds worth of
+ // bytes to the delay calculation.
+ capacity_delay_ms = (data_length + capacity_delay_error_bytes_ +
+ bytes_per_millisecond / 2) /
+ bytes_per_millisecond;
+ capacity_delay_error_bytes_ +=
+ data_length - capacity_delay_ms * bytes_per_millisecond;
+ }
int64_t network_start_time = time_now;
// Check if there already are packets on the link and change network start
diff --git a/test/fake_network_pipe.h b/test/fake_network_pipe.h
index 039cc84..d7e0c5d 100644
--- a/test/fake_network_pipe.h
+++ b/test/fake_network_pipe.h
@@ -176,6 +176,8 @@
int64_t last_log_time_;
+ int64_t capacity_delay_error_bytes_ = 0;
+
RTC_DISALLOW_COPY_AND_ASSIGN(FakeNetworkPipe);
};
