Re: [dpdk-dev] [PATCH] vhost: flush shadow tx if there is no more packets

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 2/4/20 3:47 PM, Eugenio Pérez wrote:
> The current implementation of vhost_net in packed vring tries to fill
> the shadow vector before send any actual changes to the guest. While
> this can be beneficial for the throughput, it conflicts with some
> bufferfloats methods like the linux kernel napi, that stops
> transmitting packets if there are too much bytes/buffers in the
> driver.
> 
> To solve it, we flush the shadow packets at the end of
> virtio_dev_tx_packed if we have starved the vring, i.e., the next
> buffer is not available for the device.
> 
> Since this last check can be expensive because of the atomic, we only
> check it if we have not obtained the expected (count) packets. If it
> happens to obtain "count" packets and there is no more available
> packets the caller needs to keep call virtio_dev_tx_packed again.
> 
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  lib/librte_vhost/virtio_net.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)

Applied to dpdk-next-virtio tree.

Thanks,
Maxime