Hi. On pátek 16. února 2018 23:59:52 CET Eric Dumazet wrote: > Well, no effect here on e1000e (1 Gbit) at least > > # ethtool -K eth3 sg off > Actual changes: > scatter-gather: off > tx-scatter-gather: off > tcp-segmentation-offload: off > tx-tcp-segmentation: off [requested on] > tx-tcp6-segmentation: off [requested on] > generic-segmentation-offload: off [requested on] > > # tc qd replace dev eth3 root pfifo_fast > # ./super_netperf 1 -H 7.7.7.84 -- -K cubic > 941 > # ./super_netperf 1 -H 7.7.7.84 -- -K bbr > 941 > # tc qd replace dev eth3 root fq > # ./super_netperf 1 -H 7.7.7.84 -- -K cubic > 941 > # ./super_netperf 1 -H 7.7.7.84 -- -K bbr > 941 > # tc qd replace dev eth3 root fq_codel > # ./super_netperf 1 -H 7.7.7.84 -- -K cubic > 941 > # ./super_netperf 1 -H 7.7.7.84 -- -K bbr > 941 > #
That really looks strange to me. I'm able to reproduce the effect caused by disabling scatter-gather even on the VM (using iperf3, as usual): BBR+fq_codel: sg on: 4.23 Gbits/sec sg off: 121 Mbits/sec BBR+fq: sg on: 6.38 Gbits/sec sg off: 437 Mbits/sec Reno+fq_codel: sg on: 6.74 Gbits/sec sg off: 1.37 Gbits/sec Reno+fq: sg on: 6.53 Gbits/sec sg off: 1.19 Gbits/sec Regardless of which congestion algorithm and qdisc is in use, the throughput drops, but when BBR is in use, especially with something non-fq, it drops the most. Oleksandr
