ip_tunnel: Create percpu gro_cell

In the ipip tunnel, the skb->queue_mapping is lost in ipip_rcv().
All skb will be queued to the same cell->napi_skbs.  The
gro_cell_poll is pinned to one core under load.  In production traffic,
we also see severe rx_dropped in the tunl iface and it is probably due to
this limit: skb_queue_len(&cell->napi_skbs) > netdev_max_backlog.

This patch is trying to alloc_percpu(struct gro_cell) and schedule
gro_cell_poll to process the skb in the same core.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/gro_cells.h b/include/net/gro_cells.h
index 734d9b5..0f712c0 100644 (file)
--- a/include/net/gro_cells.h
+++ b/include/net/gro_cells.h
@@ -8,25 +8,23 @@
 struct gro_cell {
        struct sk_buff_head     napi_skbs;
        struct napi_struct      napi;
-} ____cacheline_aligned_in_smp;
+};
 
 struct gro_cells {
-       unsigned int            gro_cells_mask;
-       struct gro_cell         *cells;
+       struct gro_cell __percpu        *cells;
 };
 
 static inline void gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
 {
-       struct gro_cell *cell = gcells->cells;
+       struct gro_cell *cell;
        struct net_device *dev = skb->dev;
 
-       if (!cell || skb_cloned(skb) || !(dev->features & NETIF_F_GRO)) {
+       if (!gcells->cells || skb_cloned(skb) || !(dev->features & NETIF_F_GRO)) {
                netif_rx(skb);
                return;
        }
 
-       if (skb_rx_queue_recorded(skb))
-               cell += skb_get_rx_queue(skb) & gcells->gro_cells_mask;
+       cell = this_cpu_ptr(gcells->cells);
 
        if (skb_queue_len(&cell->napi_skbs) > netdev_max_backlog) {
                atomic_long_inc(&dev->rx_dropped);
@@ -72,15 +70,12 @@ static inline int gro_cells_init(struct gro_cells *gcells, struct net_device *de
 {
        int i;
 
-       gcells->gro_cells_mask = roundup_pow_of_two(netif_get_num_default_rss_queues()) - 1;
-       gcells->cells = kcalloc(gcells->gro_cells_mask + 1,
-                               sizeof(struct gro_cell),
-                               GFP_KERNEL);
+       gcells->cells = alloc_percpu(struct gro_cell);
        if (!gcells->cells)
                return -ENOMEM;
 
-       for (i = 0; i <= gcells->gro_cells_mask; i++) {
-               struct gro_cell *cell = gcells->cells + i;
+       for_each_possible_cpu(i) {
+               struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
 
                skb_queue_head_init(&cell->napi_skbs);
                netif_napi_add(dev, &cell->napi, gro_cell_poll, 64);
@@ -91,16 +86,16 @@ static inline int gro_cells_init(struct gro_cells *gcells, struct net_device *de
 
 static inline void gro_cells_destroy(struct gro_cells *gcells)
 {
-       struct gro_cell *cell = gcells->cells;
        int i;
 
-       if (!cell)
+       if (!gcells->cells)
                return;
-       for (i = 0; i <= gcells->gro_cells_mask; i++,cell++) {
+       for_each_possible_cpu(i) {
+               struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
                netif_napi_del(&cell->napi);
                skb_queue_purge(&cell->napi_skbs);
        }
-       kfree(gcells->cells);
+       free_percpu(gcells->cells);
        gcells->cells = NULL;
 }