[dpdk-dev] [PATCH] vhost: flush shadow tx if there is no more packets
Eugenio Perez Martin
eperezma at redhat.com
Wed Feb 5 16:45:48 CET 2020
On Wed, Feb 5, 2020 at 10:48 AM Maxime Coquelin <maxime.coquelin at 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 at redhat.com>
> > ---
> > lib/librte_vhost/virtio_net.c | 27 ++++++++++++++++++++++++++-
> > 1 file changed, 26 insertions(+), 1 deletion(-)
> Applied to dpdk-next-virtio tree.
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