On Wed, 2022-02-16 at 20:00 +0800, Dust Li wrote: > This patch adds autocork support for SMC which could improve > throughput for small message by x2 ~ x4. > > The main idea is borrowed from TCP autocork with some RDMA > specific modification: > 1. The first message should never cork to make sure we won't > bring extra latency > 2. If we have posted any Tx WRs to the NIC that have not > completed, cork the new messages until: > a) Receive CQE for the last Tx WR > b) We have corked enough message on the connection > 3. Try to push the corked data out when we receive CQE of > the last Tx WR to prevent the corked messages hang in > the send queue. > > Both SMC autocork and TCP autocork check the TX completion > to decide whether we should cork or not. The difference is > when we got a SMC Tx WR completion, the data have been confirmed > by the RNIC while TCP TX completion just tells us the data > have been sent out by the local NIC. > > Add an atomic variable tx_pushing in smc_connection to make > sure only one can send to let it cork more and save CDC slot. > > SMC autocork should not bring extra latency since the first > message will always been sent out immediately. > > The qperf tcp_bw test shows more than x4 increase under small > message size with Mellanox connectX4-Lx, same result with other > throughput benchmarks like sockperf/netperf. > The qperf tcp_lat test shows SMC autocork has not increase any > ping-pong latency. > > BW test: > client: smc_run taskset -c 1 qperf smc-server -oo msg_size:1:64K:*2 \ > -t 30 -vu tcp_bw > server: smc_run taskset -c 1 qperf > > MsgSize(Bytes) TCP SMC-NoCork SMC-AutoCork > 1 2.57 MB/s 698 KB/s(-73.5%) 2.98 MB/s(16.0% ) > 2 5.1 MB/s 1.41 MB/s(-72.4%) 5.82 MB/s(14.1% ) > 4 10.2 MB/s 2.83 MB/s(-72.3%) 11.7 MB/s(14.7% ) > 8 20.8 MB/s 5.62 MB/s(-73.0%) 22.9 MB/s(10.1% ) > 16 42.5 MB/s 11.5 MB/s(-72.9%) 45.5 MB/s(7.1% ) > 32 80.7 MB/s 22.3 MB/s(-72.4%) 86.7 MB/s(7.4% ) > 64 155 MB/s 45.6 MB/s(-70.6%) 160 MB/s(3.2% ) > 128 295 MB/s 90.1 MB/s(-69.5%) 273 MB/s(-7.5% ) > 256 539 MB/s 179 MB/s(-66.8%) 610 MB/s(13.2% ) > 512 943 MB/s 360 MB/s(-61.8%) 1.02 GB/s(10.8% ) > 1024 1.58 GB/s 710 MB/s(-56.1%) 1.91 GB/s(20.9% ) > 2048 2.47 GB/s 1.34 GB/s(-45.7%) 2.92 GB/s(18.2% ) > 4096 2.86 GB/s 2.5 GB/s(-12.6%) 2.4 GB/s(-16.1%) > 8192 3.89 GB/s 3.14 GB/s(-19.3%) 4.05 GB/s(4.1% ) > 16384 3.29 GB/s 4.67 GB/s(41.9% ) 5.09 GB/s(54.7% ) > 32768 2.73 GB/s 5.48 GB/s(100.7%) 5.49 GB/s(101.1%) > 65536 3 GB/s 4.85 GB/s(61.7% ) 5.24 GB/s(74.7% ) > > Latency test: > client: smc_run taskset -c 1 qperf smc-server -oo msg_size:1:64K:*2 \ > -t 30 -vu tcp_lat > server: smc_run taskset -c 1 qperf > > MsgSize SMC-NoCork SMC-AutoCork > 1 9.7 us 9.6 us( -1.03%) > 2 9.43 us 9.39 us( -0.42%) > 4 9.6 us 9.35 us( -2.60%) > 8 9.42 us 9.2 us( -2.34%) > 16 9.13 us 9.43 us( 3.29%) > 32 9.19 us 9.5 us( 3.37%) > 64 9.38 us 9.5 us( 1.28%) > 128 9.9 us 9.29 us( -6.16%) > 256 9.42 us 9.26 us( -1.70%) > 512 10 us 9.45 us( -5.50%) > 1024 10.4 us 9.6 us( -7.69%) > 2048 10.4 us 10.2 us( -1.92%) > 4096 11 us 10.5 us( -4.55%) > 8192 11.7 us 11.8 us( 0.85%) > 16384 14.5 us 14.2 us( -2.07%) > 32768 19.4 us 19.3 us( -0.52%) > 65536 28.1 us 28.8 us( 2.49%) This is quite an impressive improvement! Thanks for your effort! Could you share a bit more about how you performed these tests to give a bit more context and allow us to reproduce them on s390. I'm assuming the ConnectX-4 Lx card you're using is a 50 Gb/s model? Are you doing these tests on two bare metal hosts, one host with client/server namespaces, or between VMs? If it's namespaces or VMs are you using VFs from the same card/port or different cards. If it is two cards/ports do you have a switch or a cross cable between them?
