[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 added inline comments.

INLINE COMMENTS

> v.maffione_gmail.com wrote in pci_virtio_net.c:496
> In theory this NIOCRXSYNC is not needed, because poll() or kqueue_wait() calls NIOCRXSYNC internally. This works perfectly with poll(), at least. As far as I know bhyve uses kqueue to wait on the netmap file descriptor. What happens if you remove this ioctl()?

I agree, it seems there are no need to call ioctl(..., NIOCRXSYNC, ...). And I observed a some throughput increase (~300-500 MBit/s 1500 MTU), when RX packet occupied one netmap buffer. This is explained by the fact that additional syscall was gone.

But I need some time to investigate how this affects performance with a large MTU.

CHANGES SINCE LAST ACTION
  https://reviews.freebsd.org/D20276/new/

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

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

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