For the record: I've tracked this down to a pair of commmits, the first of which landed in -35 (released in -36) the second in -37.
The first: https://lkml.org/lkml/2018/6/5/765 The second: https://lkml.org/lkml/2018/6/24/161 In the interim state, it was casting a u64 to a u32, which truncates to the least-significant 32 bits. This was, from what I could see using tcpdump and other tools, causing the TCP window size to truncate to a very small number, leading to hilariously slow network traffic. Further, it seems (although I haven't yet got the whole logic chain in my head) that the TCP algorithm could never get itself out of this state again, so the connection was then permanently stuck in a slow state. The two commits were originally from the one author, within a second of each other, back in Dec 2017. They really needed to be pulled in together. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1796895 Title: Kernel 4.15.0-36 network performance regression To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1796895/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
