stmmac: tune rx copy via threshold.

There is a threshold now used to also limit the skb allocation
when use zero-copy. This is to avoid that there are incoherence
in the ring due to a failure on skb allocation under very
aggressive testing and under low memory conditions.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 221f5cd..d6c244f 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -75,6 +75,7 @@ struct stmmac_priv {
        unsigned int dirty_rx;
        unsigned int dma_buf_sz;
        unsigned int rx_copybreak;
+       unsigned int rx_zeroc_thresh;
        u32 rx_riwt;
        int hwts_rx_en;
        dma_addr_t *rx_skbuff_dma;

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 2ffe8dd..4c5ce98 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -72,6 +72,7 @@ module_param(phyaddr, int, S_IRUGO);
 MODULE_PARM_DESC(phyaddr, "Physical device address");
 
 #define STMMAC_TX_THRESH       (DMA_TX_SIZE / 4)
+#define STMMAC_RX_THRESH       (DMA_RX_SIZE / 4)
 
 static int flow_ctrl = FLOW_OFF;
 module_param(flow_ctrl, int, S_IRUGO | S_IWUSR);
@@ -2138,6 +2139,14 @@ static void stmmac_rx_vlan(struct net_device *dev, struct sk_buff *skb)
 }
 
 
+static inline int stmmac_rx_threshold_count(struct stmmac_priv *priv)
+{
+       if (priv->rx_zeroc_thresh < STMMAC_RX_THRESH)
+               return 0;
+
+       return 1;
+}
+
 /**
  * stmmac_rx_refill - refill used skb preallocated buffers
  * @priv: driver private structure
@@ -2162,8 +2171,15 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
                        struct sk_buff *skb;
 
                        skb = netdev_alloc_skb_ip_align(priv->dev, bfsize);
-                       if (unlikely(!skb))
+                       if (unlikely(!skb)) {
+                               /* so for a while no zero-copy! */
+                               priv->rx_zeroc_thresh = STMMAC_RX_THRESH;
+                               if (unlikely(net_ratelimit()))
+                                       dev_err(priv->device,
+                                               "fail to alloc skb entry %d\n",
+                                               entry);
                                break;
+                       }
 
                        priv->rx_skbuff[entry] = skb;
                        priv->rx_skbuff_dma[entry] =
@@ -2179,9 +2195,13 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
 
                        priv->hw->mode->refill_desc3(priv, p);
 
+                       if (priv->rx_zeroc_thresh > 0)
+                               priv->rx_zeroc_thresh--;
+
                        if (netif_msg_rx_status(priv))
                                pr_debug("\trefill entry #%d\n", entry);
                }
+
                wmb();
                priv->hw->desc->set_rx_owner(p);
                wmb();
@@ -2285,7 +2305,8 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
                                                 frame_len, status);
                        }
 
-                       if (unlikely(frame_len < priv->rx_copybreak)) {
+                       if (unlikely((frame_len < priv->rx_copybreak) ||
+                                    stmmac_rx_threshold_count(priv))) {
                                skb = netdev_alloc_skb_ip_align(priv->dev,
                                                                frame_len);
                                if (unlikely(!skb)) {
@@ -2320,6 +2341,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
                                }
                                prefetch(skb->data - NET_IP_ALIGN);
                                priv->rx_skbuff[entry] = NULL;
+                               priv->rx_zeroc_thresh++;
 
                                skb_put(skb, frame_len);
                                dma_unmap_single(priv->device,