On Wed, 2015-01-07 at 13:31 +0000, Erik Grinaker wrote: > On 06 Jan 2015, at 22:00, Yuchung Cheng <ych...@google.com> wrote: > > On Tue, Jan 6, 2015 at 1:04 PM, Erik Grinaker <e...@bengler.no> wrote: > >> > >>> On 06 Jan 2015, at 20:26, Erik Grinaker <e...@bengler.no> wrote: > >> This still doesn’t explain why it works with older kernels, but not newer > >> ones. I’m thinking it’s > > probably some minor change, which gets amplified by the lack of SACKs > > on the loadbalancer. Anyway, I’ll bring it up with Amazon. > > can you post traces with the older kernels? > > Here is a dump using 3.11.10 against a non-SACK-enabled loadbalancer: > > http://abstrakt.bengler.no/tcp-issues-s3-nosack-3.11.10.pcap.bz2 > > The transfer shows lots of DUPACKs and retransmits, but this does not > seem to have as bad an effect as it did with the failing transfer we > saw on newer kernels: > > http://abstrakt.bengler.no/tcp-issues-s3-failure.pcap.bz2 > > One big difference, which Rick touched on earlier, is that the newer > kernels keep sending TCP window updates as it’s going through the > retransmits. The older kernel does not do this.
The new kernel is the receiver : It does no retransmits. Increasing window in ACK packets should not prevent sender into retransmitting missing packets. Sender is not a linux host and is very buggy IMO : If receiver advertises a too big window, sender decides to not retransmit in some cases. You can play with /proc/sys/net/ipv4/tcp_rmem and adopt very low values to work around the sender bug. ( Or use SO_RCVBUF in receiver application) -- 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/
