Public bug reported: [Impact]
AWS has seen some customers reporting networking performance degradation after they upgraded their Ubuntu instanceses. This regression is highly impacting customers who are using MTU=9000 (which is the default in EC2). [Test case] Bug reproduced internally in AWS (no test case provided), but apparently it is very easy to reproduce simply by measuring networking performance. [Fix] AWS worked internally and found that the regression has been introduced by: a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB") To solve the problem we need to apply the following upstream commit that explicitly fixes the problem introduced by the commit above: 33ae7b5bb841 ("tcp: select sane initial rcvq_space.space for big MSS") [Regression potential] Upstream fix that is only affecting the initial TCP buffer space and allows the TCP window size to be dynamically increased, basically restoring the previous (correct) behavior, so regression potential is minimal. ** Affects: linux-aws (Ubuntu) Importance: Undecided Status: New ** Affects: linux-aws (Ubuntu Bionic) Importance: High Status: New ** Affects: linux-aws (Ubuntu Focal) Importance: High Status: New ** Affects: linux-aws (Ubuntu Groovy) Importance: High Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1910200 Title: aws: network performance regression due to initial TCP receive buffer size change To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-aws/+bug/1910200/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs