On Tue, 2015-01-06 at 16:11 +0000, Erik Grinaker wrote: > > On 06 Jan 2015, at 16:04, Eric Dumazet <eric.duma...@gmail.com> wrote: > > On Tue, 2015-01-06 at 15:14 +0000, Erik Grinaker wrote: > >> (CCing Yuchung, as his name comes up in the relevant commits) > >> > >> After upgrading from Ubuntu 12.04.5 to 14.04.1 we have begun seeing > >> intermittent TCP connection hangs for HTTP image requests against > >> Amazon S3. 3-5% of requests will suddenly stall in the middle of the > >> transfer before timing out. We see this problem across a range of > >> servers, in several data centres and networks, all located in Norway. > >> > >> A packet dump [1] shows repeated ACK retransmits for some of the > >> requests. Using Ubuntu mainline kernels, we found the problem to have > >> been introduced between 3.11.10 and 3.12.0, possibly in > >> 0f7cc9a3c2bd89b15720dbf358e9b9e62af27126. The problem is also present > >> in 3.18.1. Disabling tcp_window_scaling seems to solve it, but has > >> obvious drawbacks for transfer speeds. Other sysctls do not seem to > >> affect it. > >> > >> I am not sure if this is fundamentally a kernel bug or a network > >> issue, but we did not see this problem with older kernels. > >> > >> [1] http://abstrakt.bengler.no/tcp-issues-s3.pcap.bz2 > > > > > > CC netdev > > > > This looks like the bug we fixed here : > > > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=39bb5e62867de82b269b07df900165029b928359 > > Has that patch gone into a release? Because the problem persists with 3.18.1.
Patch is in 3.18.1 yes. So thats a separate issue. Can you confirm pcap was taken at receiver (195.159.221.106), not sender (54.231.136.74) , and on which host is running the 'buggy kernel' ? If the sender is broken, changing the kernel on receiver wont help. BTW not using sack (on 54.231.132.98) is terrible for performance in lossy environments. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
