Hello: We used to orphan packets before transmission for virtio-net. This breaks socket accounting and can lead serveral functions won't work, e.g:
- Byte Queue Limit depends on tx completion nofication to work. - Packet Generator depends on tx completion nofication for the last transmitted packet to complete. - TCP Small Queue depends on proper accounting of sk_wmem_alloc to work. This series tries to solve the issue by enabling tx interrupts. To minize the performance impacts of this, several optimizations were used: - In guest side, virtqueue_enable_cb_delayed() was used to delay the tx interrupt untile 3/4 pending packets were sent. - In host side, interrupt coalescing were used to reduce tx interrupts. Performance test results[1] (tx-frames 16 tx-usecs 16) shows: - For guest receiving. No obvious regression on throughput were noticed. More cpu utilization were noticed in few cases. - For guest transmission. Very huge improvement on througput for small packet transmission were noticed. This is expected since TSQ and other optimization for small packet transmission work after tx interrupt. But will use more cpu for large packets. - For TCP_RR, regression (10% on transaction rate and cpu utilization) were found. Tx interrupt won't help but cause overhead in this case. Using more aggressive coalescing parameters may help to reduce the regression. Changes from RFC V3: - Don't free tx packets in ndo_start_xmit() - Add interrupt coalescing support for virtio-net Changes from RFC v2: - clean up code, address issues raised by Jason Changes from RFC v1: - address comments by Jason Wang, use delayed cb everywhere - rebased Jason's patch on top of mine and include it (with some tweaks) Please reivew. Comments were more than welcomed. [1] Performance Test result: Environment: - Two Intel(R) Xeon(R) CPU E5620 @ 2.40GHz machines connected back to back with 82599ES cards. - Both host and guest were net-next.git plus the patch - Coalescing parameters for the card: Adaptive RX: off TX: off rx-usecs: 1 rx-frames: 0 tx-usecs: 0 tx-frames: 0 - Vhost_net was enabled and zerocopy was disabled - Tests was done by netperf-2.6 - Guest has 2 vcpus with single queue virtio-net Results: - Numbers of square brackets are whose significance is grater than 95% Guest RX: size/sessions/+throughput/+cpu/+per_cpu_throughput/ 64/1/+2.0326/[+6.2807%]/-3.9970%/ 64/2/-0.2104%/[+3.2012%]/[-3.3058%]/ 64/4/+1.5956%/+2.2451%/-0.6353%/ 64/8/+1.1732%/+3.5123%/-2.2598%/ 256/1/+3.7619%/[+5.8117%]/-1.9372%/ 256/2/-0.0661%/[+3.2511%]/-3.2127%/ 256/4/+1.1435%/[-8.1842%]/[+10.1591%]/ 256/8/[+2.2447%]/[+6.2044%]/[-3.7283%]/ 1024/1/+9.1479%/[+12.0997%]/[-2.6332%]/ 1024/2/[-17.3341%]/[+0.0000%]/[-17.3341%]/ 1024/4/[-0.6284%]/-1.0376%/+0.4135%/ 1024/8/+1.1444%/-1.6069%/+2.7961%/ 4096/1/+0.0401%/-0.5993%/+0.6433%/ 4096/2/[-0.5894%]/-2.2071%/+1.6542%/ 4096/4/[-0.5560%]/-1.4969%/+0.9553%/ 4096/8/-0.3362%/+2.7086%/-2.9645%/ 16384/1/-0.0285%/+0.7247%/-0.7478%/ 16384/2/-0.5286%/+0.3287%/-0.8545%/ 16384/4/-0.3297%/-2.0543%/+1.7608%/ 16384/8/+1.0932%/+4.0253%/-2.8187%/ 65535/1/+0.0003%/-0.1502%/+0.1508%/ 65535/2/[-0.6065%]/+0.2309%/-0.8355%/ 65535/4/[-0.6861%]/[+3.9451%]/[-4.4554%]/ 65535/8/+1.8359%/+3.1590%/-1.2825%/ Guest RX: size/sessions/+throughput/+cpu/+per_cpu_throughput/ 64/1/[+65.0961%]/[-8.6807%]/[+80.7900%]/ 64/2/[+6.0288%]/[-2.2823%]/[+8.5052%]/ 64/4/[+5.9038%]/[-2.1834%]/[+8.2677%]/ 64/8/[+5.4154%]/[-2.1804%]/[+7.7651%]/ 256/1/[+184.6462%]/[+4.8906%]/[+171.3742%]/ 256/2/[+46.0731%]/[-8.9626%]/[+60.4539%]/ 256/4/[+45.8547%]/[-8.3027%]/[+59.0612%]/ 256/8/[+45.3486%]/[-8.4024%]/[+58.6817%]/ 1024/1/[+432.5372%]/[+3.9566%]/[+412.2689%]/ 1024/2/[-1.4207%]/[-23.6426%]/[+29.1025%]/ 1024/4/-0.1003%/[-13.6416%]/[+15.6804%]/ 1024/8/[+0.2200%]/[+2.0634%]/[-1.8061%]/ 4096/1/[+18.4835%]/[-46.1508%]/[+120.0283%]/ 4096/2/+0.1770%/[-26.2780%]/[+35.8848%]/ 4096/4/-0.1012%/-0.7353%/+0.6388%/ 4096/8/-0.6091%/+1.4159%/-1.9968%/ 16384/1/-0.0424%/[+11.9373%]/[-10.7021%]/ 16384/2/+0.0482%/+2.4685%/-2.3620%/ 16384/4/+0.0840%/[+5.3587%]/[-5.0064%]/ 16384/8/+0.0048%/[+5.0176%]/[-4.7733%]/ 65535/1/-0.0095%/[+10.9408%]/[-9.8705%]/ 65535/2/+0.1515%/[+8.1709%]/[-7.4137%]/ 65535/4/+0.0203%/[+5.4316%]/[-5.1325%]/ 65535/8/+0.1427%/[+6.2753%]/[-5.7705%]/ size/sessions/+trans.rate/+cpu/+per_cpu_trans.rate/ 64/1/+0.2346%/[+11.5080%]/[-10.1099%]/ 64/25/[-10.7893%]/-0.5791%/[-10.2697%]/ 64/50/[-11.5997%]/-0.3429%/[-11.2956%]/ 256/1/+0.7219%/[+13.2374%]/[-11.0524%]/ 256/25/-6.9567%/+0.8887%/[-7.7763%]/ 256/50/[-4.8814%]/-0.0338%/[-4.8492%]/ 4096/1/-1.6061%/-0.7561%/-0.8565%/ 4096/25/[+2.2120%]/[+1.0839%]/+1.1161%/ 4096/50/[+5.6180%]/[+3.2116%]/[+2.3315%]/ Jason Wang (4): virtio_net: enable tx interrupt virtio-net: optimize free_old_xmit_skbs stats virtio-net: add basic interrupt coalescing support vhost_net: interrupt coalescing support Michael S. Tsirkin (1): virtio_net: bql drivers/net/virtio_net.c | 211 ++++++++++++++++++++++++++++++++-------- drivers/vhost/net.c | 200 +++++++++++++++++++++++++++++++++++-- include/uapi/linux/vhost.h | 12 +++ include/uapi/linux/virtio_net.h | 12 +++ 4 files changed, 383 insertions(+), 52 deletions(-) -- 1.8.3.1 -- 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/
