path: root/src/network/access/http2
diff options
authorTimur Pocheptsov <>2017-10-12 15:02:09 +0200
committerTimur Pocheptsov <>2017-10-16 16:54:32 +0000
commita520c179b89610248ef97f614d6b831ccee54c6b (patch)
tree553faf7adb5aa9339ed23f062975fa85a11d8431 /src/network/access/http2
parent65eed6d5978738b06e047c9bd5d162b2596759f7 (diff)
HTTP/2 protocol handler: tweak receive window sizes
We were using the default ones, provided by RFC7540. It appears they are way too restrictive and conservative: when downloading something relatively big, a stream keeps spending the whole session/its own 'recv' windows and thus we have to constantly send WINDOW_UPDATE frames. This significantly slows down our HTTP/2 implementation, making it orders of magnitude slower than HTTP/1.1. To fix this: - We send SETTINGS_INITIAL_WINDOW_SIZE in the first SETTINGS frame to inform our peer that per-stream WINDOW is bigger than 64Kb - We increase the session's receive window size. Task-number: QTBUG-63722 Change-Id: I31312fcfd5f0fc0aee6aaa5d3562cc7d1b931adc Reviewed-by: Edward Welbourne <>
Diffstat (limited to 'src/network/access/http2')
2 files changed, 14 insertions, 2 deletions
diff --git a/src/network/access/http2/http2protocol.cpp b/src/network/access/http2/http2protocol.cpp
index 54811aeab0..bb3d6bf575 100644
--- a/src/network/access/http2/http2protocol.cpp
+++ b/src/network/access/http2/http2protocol.cpp
@@ -216,6 +216,8 @@ Frame default_SETTINGS_frame()
// MAX frame size (16 kb), disable/enable PUSH_PROMISE
+ builder.append(Settings::INITIAL_WINDOW_SIZE_ID);
+ builder.append(initialStreamReceiveWindowSize);
diff --git a/src/network/access/http2/http2protocol_p.h b/src/network/access/http2/http2protocol_p.h
index b26ff0e9f4..c64e960002 100644
--- a/src/network/access/http2/http2protocol_p.h
+++ b/src/network/access/http2/http2protocol_p.h
@@ -129,10 +129,20 @@ enum Http2PredefinedParameters
maxConcurrentStreams = 100 // HTTP/2, 6.5.2
-// It's int, it has internal linkage, it's ok to have it in headers -
-// no ODR violation is possible.
+// These are ints, const, they have internal linkage, it's ok to have them in
+// headers - no ODR violation.
const quint32 lastValidStreamID((quint32(1) << 31) - 1); // HTTP/2, 5.1.1
+// The default size of 64K is too small and limiting: if we use it, we end up
+// sending WINDOW_UPDATE frames on a stream/session all the time, for each
+// 2 DATE frames of size 16K (also default) we'll send a WINDOW_UPDATE frame
+// for a given stream and have a download speed order of magnitude lower than
+// our own HTTP/1.1 protocol handler. We choose a bigger window size (normally,
+// HTTP/2 servers are not afraid to immediately set it to possible max anyway)
+// and split this window size between our concurrent streams.
+const qint32 initialSessionReceiveWindowSize = defaultSessionWindowSize * 10000;
+const qint32 initialStreamReceiveWindowSize = initialSessionReceiveWindowSize / maxConcurrentStreams;
extern const Q_AUTOTEST_EXPORT char Http2clientPreface[clientPrefaceLength];
void prepare_for_protocol_upgrade(QHttpNetworkRequest &request);