Details
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Bug
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Resolution: Done
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P2: Important
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6.2.4, 6.3.1, 6.4.0 Beta2
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None
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9540a4eb90 (qt/qtbase/dev) 9540a4eb90 (qt/tqtc-qtbase/dev) 9fd40c04d1 (qt/qtbase/6.4) 9fd40c04d1 (qt/tqtc-qtbase/6.4) 825ef509c5 (qt/qtbase/6.3) 825ef509c5 (qt/tqtc-qtbase/6.3) 118558c5b2 (qt/tqtc-qtbase/6.2)
Description
First off: the numbers here come from testing on a 400MBit/s fiber line, but the actual slow-down is independent of the Internet speed.
Please see the attached test program that uses QNAM to download a ~60MB file from a specific HTTP server. With no special config, the download in 6.2.4, 6.3.1 and 6.4.0 is very slow at <200 KB/s.
Setting QNetworkRequest::Http2AllowedAttribute to false speeds the download up to where it was before with Qt 5: roughly 4-5MB/s.
Just build it, run it and watch the output. You can just uncomment the setAttribute line to test without HTTP2.
I could only reproduce this problem with this specific server at ldraw.org. Please be gentle when testing and don't hammer their server like crazy: this is a non-profit organization run by volunteers
For comparison curl in http2 mode is downloading at around 5-8MB/s:
curl -o /dev/null --http2 'https://www.ldraw.org/library/updates/complete.zip' % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 63.6M 100 63.6M 0 0 5651k 0 0:00:11 0:00:11 --:--:-- 6075k