[PATCH net-next v3 6/8] virtio-net: xsk zero copy xmit kick by threshold

[Xuan Zhuo]

After testing, the performance of calling kick every time is not stable.
And if all the packets are sent and kicked again, the performance is not
good. So add a module parameter to specify how many packets are sent to
call a kick.

8 is a relatively stable value with the best performance.

Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
Reviewed-by: Dust Li <dust...@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 259fafcf6028..d7e95f55478d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -29,10 +29,12 @@ module_param(napi_weight, int, 0444);
 
 static bool csum = true, gso = true, napi_tx = true;
 static int xsk_budget = 32;
+static int xsk_kick_thr = 8;
 module_param(csum, bool, 0444);
 module_param(gso, bool, 0444);
 module_param(napi_tx, bool, 0644);
 module_param(xsk_budget, int, 0644);
+module_param(xsk_kick_thr, int, 0644);
 
 /* FIXME: MTU in config. */
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
@@ -2612,6 +2614,8 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
        struct xdp_desc desc;
        int err, packet = 0;
        int ret = -EAGAIN;
+       int need_kick = 0;
+       int kicks = 0;
 
        if (sq->xsk.last_desc.addr) {
                err = virtnet_xsk_xmit(sq, pool, &sq->xsk.last_desc);
@@ -2619,6 +2623,7 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
                        return -EBUSY;
 
                ++packet;
+               ++need_kick;
                --budget;
                sq->xsk.last_desc.addr = 0;
        }
@@ -2642,13 +2647,25 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
                }
 
                ++packet;
+               ++need_kick;
+               if (need_kick > xsk_kick_thr) {
+                       if (virtqueue_kick_prepare(sq->vq) &&
+                           virtqueue_notify(sq->vq))
+                               ++kicks;
+
+                       need_kick = 0;
+               }
        }
 
        if (packet) {
-               if (virtqueue_kick_prepare(sq->vq) &&
-                   virtqueue_notify(sq->vq)) {
+               if (need_kick) {
+                       if (virtqueue_kick_prepare(sq->vq) &&
+                           virtqueue_notify(sq->vq))
+                               ++kicks;
+               }
+               if (kicks) {
                        u64_stats_update_begin(&sq->stats.syncp);
-                       sq->stats.kicks += 1;
+                       sq->stats.kicks += kicks;
                        u64_stats_update_end(&sq->stats.syncp);
                }
 
-- 
2.31.0