https://bugs.kde.org/show_bug.cgi?id=481634
Bug ID: 481634
Summary: Enabling µTP causes KTorrent to exceed upload speed
limit
Classification: Applications
Product: ktorrent
Version: 22.12.3
Platform: Kubuntu
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: joris.guis...@gmail.com
Reporter: andy...@mail.ru
Target Milestone: ---
SUMMARY
When I enable µTorrent protocol (µTP) in the settings, and have an upload
network bandwidth limit set, the actual outbound bitrate exceeds the set limit
(provided that there are enough downloads and uploads active).
STEPS TO REPRODUCE
1. In the KTorrent settings, on the Network tab, enable both "Use the µTorrent
transport protocol (µTP)" and "Only use µTP". (The problem also reproduces with
only the first option enabled, but to a lesser degree.)
2. On the same Network tab, set maximum download and upload speeds that are
below the actual network bandwith. For example, I have a 100 Mbit
upload/download bandwidth, and I set 9216 KiB/s download and 8704 KiB/s upload
speeds. These limits roughly correspond to 75.5 Mbit/s and 71.3 Mbit/s,
respectively.
3. Have a number of torrents that are seeding and a number of torrents that are
being downloaded. The total download/upload speed should be limited by the set
speed limits.
4. Watch the actual network utilization, as reported through
/sys/class/net/${interface}/statistics/rx_bytes and
/sys/class/net/${interface}/statistics/tx_bytes. I'm using a custom shell
script that monitors these values, but it should be possible to use System
Monitor for this as well.
OBSERVED RESULT
The actual outbound bitrate significantly exceeds the set limit. In my example,
I'm consistently seeing 90 or even 95+ Mbit/s of outbound bitrate, i.e. about
the actual network uplink limit. I even tried reducing the upload limit to e.g.
8192 KiB/s but that didn't affect the actual outbound bitrate.
Naturally, I don't have any other network activity.
EXPECTED RESULT
I realize that there must be some protocol overhead, and the actual outbound
bitrate may be higher than the limit in the settings. However, that overhead
should be either negligibly small, or included in the limit. Otherwise, the
upload limit in the settings is not serving its purpose.
For example, when I disable µTP completely, I'm seeing download/upload bitrates
much closer to the set limits. In particular, the outbound bitrate is somewhere
around 75 Mbit/s.
SOFTWARE/OS VERSIONS
Operating System: Kubuntu 22.04
KDE Plasma Version: 5.24.7
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3
KTorrent Version: 21.12.3
Kernel Version: 6.5.0-17-lowlatency (64-bit)
Graphics Platform: X11
Processors: 16 × 12th Gen Intel® Core™ i7-12700K
Memory: 31.1 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2
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