On Tue, 2020-11-03 at 09:46 -0800, David Awogbemila wrote:
> This patch lets the driver reuse buffers that have been freed by the
> networking stack.
>
> In the raw addressing case, this allows the driver avoid allocating
> new
> buffers.
> In the qpl case, the driver can avoid copies.
>
> Signed-off-by: David Awogbemila <awogbem...@google.com>
> ---
> drivers/net/ethernet/google/gve/gve.h | 10 +-
> drivers/net/ethernet/google/gve/gve_rx.c | 194 +++++++++++++++----
> ----
> + if (len <= priv->rx_copybreak) {
> + /* Just copy small packets */
> + skb = gve_rx_copy(dev, napi, page_info, len);
> + u64_stats_update_begin(&rx->statss);
> + rx->rx_copied_pkt++;
> + rx->rx_copybreak_pkt++;
> + u64_stats_update_end(&rx->statss);
> + } else {
> + bool can_flip = gve_rx_can_flip_buffers(dev);
> + int recycle = 0;
> +
> + if (can_flip) {
> + recycle = gve_rx_can_recycle_buffer(page_info-
> >page);
> + if (recycle < 0) {
> + gve_schedule_reset(priv);
How would a reset solve anything if your driver is handling pages with
"bad" refcount, i don't agree here that reset is the best course of
action, all you can do here is warn and leak the page ...
this is a critical driver bug and not something that user should
expect.
> +
> + } else {
> + /* It is possible that the networking stack has
> already
> + * finished processing all outstanding packets
> in the buffer
> + * and it can be reused.
> + * Flipping is unnecessary here - if the
> networking stack still
> + * owns half the page it is impossible to tell
> which half. Either
> + * the whole page is free or it needs to be
> replaced.
> + */
> + int recycle =
> gve_rx_can_recycle_buffer(page_info->page);
> +
> + if (recycle < 0) {
> + gve_schedule_reset(priv);
> + return false;
Same.
