Re: [PATCH RFC v3 0/3] virtio_net: enabling tx interrupts

From: Jason Wang
Date: Mon Dec 01 2014 - 05:14:43 EST

On 10/20/2014 02:52 PM, Michael S. Tsirkin wrote:
RFC patches to enable tx interrupts.
This is to demonstrate how this can be done without
core virtio changes, and to make sure I understand
the new APIs correctly.

Testing TBD, I was asked for a version for early testing.

Applies on top of patch: "virtio_net: fix use after free"
that I recently sent.

Changes from v3:
clean up code, address issues raised by Jason
Changes from v1:
address comments by Jason Wang, use delayed cb everywhere
rebased Jason's patch on top of mine and include it (with some tweaks)

Jason Wang (1):
virtio-net: optimize free_old_xmit_skbs stats

Michael S. Tsirkin (2):
virtio_net: enable tx interrupt
virtio_net: bql

drivers/net/virtio_net.c | 144 +++++++++++++++++++++++++++++++++--------------
1 file changed, 101 insertions(+), 43 deletions(-)

I've run a full tests on this series and see huge regression when zerocopy is disabled. Looks like the reason is zerocopy could coalescing tx completion which greatly reduce the number of tx interrupts.

I will post RFC V4 shortly with interrupt coalescing support. In this version I remove the tx packet cleanup in ndo_start_xmit() since it may reduce the effects of interrupt coalescing.
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