[Differential] D20276: [bhyve][virtio-net] Allow guest VM's to set JUMBO MTU in case of using the VALE switch.

[aleksandr.fedorov_itglobal.com (Aleksandr Fedorov)]

aleksandr.fedorov_itglobal.com created this revision.
aleksandr.fedorov_itglobal.com added reviewers: bhyve, jhb, rgrimes, krion, v.maffione_gmail.com.
Herald added a subscriber: bcran.

REVISION SUMMARY
  Сurrent implementation of the virtio-net backend doesn't allow to transfer of packets larger than the netmap(4) buffer size (2048) or maximum guest descriptor size for tap(4) case. The reason is that there is no support for merge-able buffers (VIRTIO_NET_F_MRG_RXBUF in virtio specifications). See PR: 215737 This significantly limits the TCP throughput.
  
  This patch adds support for mergable buffers using netmap's ability to chain it's own buffers (see NS _MOREFRAG, netmap(4)). The same approach is used by QEMU (virtio-net + netmap backend).
  
  We are seeing a significant increase in throughput both for transferring data between VM's on the same host, and between VM's on different hosts. See tests below.

TEST PLAN
  **1. 'iperf3 -c X.X.X.X -t 60 -R' between 2 Ubuntu 16.04 VM's through VALE switch.**
  
  MTU 1500. VM - virtio-net - VALE - virtio-net - VM:
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec  28.6 GBytes  4.09 Gbits/sec    3             sender
  [  5]   0.00-60.04  sec  28.6 GBytes  4.09 Gbits/sec                  receiver
  
  MTU 3000. VM - virtio-net - VALE - virtio-net - VM (MTU 3000):
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec  51.8 GBytes  7.42 Gbits/sec  651             sender
  [  5]   0.00-60.04  sec  51.8 GBytes  7.42 Gbits/sec                  receiver
  
  MTU 9000. VM - virtio-net - VALE - virtio-net - VM:
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec  99.7 GBytes  14.3 Gbits/sec  100             sender
  [  5]   0.00-60.04  sec  99.7 GBytes  14.3 Gbits/sec                  receiver
  
  MTU 16000. VM - virtio-net - VALE - virtio-net - VM:
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec   122 GBytes  17.5 Gbits/sec    0             sender
  [  5]   0.00-60.04  sec   122 GBytes  17.5 Gbits/sec                  receiver
  
  MTU 32000. VM - virtio-net - VALE - virtio-net - VM:
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec   152 GBytes  21.7 Gbits/sec   64             sender
  [  5]   0.00-60.04  sec   152 GBytes  21.7 Gbits/sec                  receiver
  
  MTU 64000. VM - virtio-net - VALE - virtio-net - VM:
  
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  5]   0.00-60.04  sec   220 GBytes  31.4 Gbits/sec   60             sender
  [  5]   0.00-60.04  sec   220 GBytes  31.4 Gbits/sec                  receiver
  
  **2. 'iperf3 -c X.X.X.X -t 60 -R' between 2 FreeBSD 12 RELEASE VM's through VALE switch.**
  
  MTU 1500. VM - virtio-net - VALE - virtio-net - VM: 1.30 Gbits/sec
  MTU 3000. VM - virtio-net - VALE - virtio-net - VM: 2.14 Gbits/sec
  MTU 9000. VM - virtio-net - VALE - virtio-net - VM: 4.80 Gbits/sec
  MTU 16000. VM - virtio-net - VALE - virtio-net - VM: 7.25 Gbits/sec
  MTU 32000. VM - virtio-net - VALE - virtio-net - VM: 12.8 Gbits/sec
  MTU 64000. VM - virtio-net - VALE - virtio-net - VM: 13.3 Gbits/sec

REVISION DETAIL
  https://reviews.freebsd.org/D20276

AFFECTED FILES
  usr.sbin/bhyve/pci_virtio_net.c

EMAIL PREFERENCES
  https://reviews.freebsd.org/settings/panel/emailpreferences/

To: aleksandr.fedorov_itglobal.com, #bhyve, jhb, rgrimes, krion, v.maffione_gmail.com
Cc: freebsd-virtualization-list, evgueni.gavrilov_itglobal.com, bcran
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