[Xen-devel] [PATCH net-next v3 5/9] xen-netback: Add stat counters for zerocopy

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

These counters help determine how often the buffers had to be copied. Also
they help find out if packets are leaked, as if "sent != success + fail",
there are probably packets never freed up properly.

Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
---
 drivers/net/xen-netback/common.h    |    3 +++
 drivers/net/xen-netback/interface.c |   15 +++++++++++++++
 drivers/net/xen-netback/netback.c   |    9 ++++++++-
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 419e63c..e3c28ff 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -155,6 +155,9 @@ struct xenvif {
 
        /* Statistics */
        unsigned long rx_gso_checksum_fixup;
+       unsigned long tx_zerocopy_sent;
+       unsigned long tx_zerocopy_success;
+       unsigned long tx_zerocopy_fail;
 
        /* Miscellaneous private stuff. */
        struct net_device *dev;
diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index af5216f..75fe683 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -239,6 +239,21 @@ static const struct xenvif_stat {
                "rx_gso_checksum_fixup",
                offsetof(struct xenvif, rx_gso_checksum_fixup)
        },
+       /* If (sent != success + fail), there are probably packets never
+        * freed up properly!
+        */
+       {
+               "tx_zerocopy_sent",
+               offsetof(struct xenvif, tx_zerocopy_sent),
+       },
+       {
+               "tx_zerocopy_success",
+               offsetof(struct xenvif, tx_zerocopy_success),
+       },
+       {
+               "tx_zerocopy_fail",
+               offsetof(struct xenvif, tx_zerocopy_fail)
+       },
 };
 
 static int xenvif_get_sset_count(struct net_device *dev, int string_set)
diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index a1b03e4..e2dd565 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1611,8 +1611,10 @@ static int xenvif_tx_submit(struct xenvif *vif, int 
budget)
                 * skb_copy_ubufs while we are still in control of the skb. E.g.
                 * the __pskb_pull_tail earlier can do such thing.
                 */
-               if (skb_shinfo(skb)->destructor_arg)
+               if (skb_shinfo(skb)->destructor_arg) {
                        skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+                       vif->tx_zerocopy_sent++;
+               }
 
                netif_receive_skb(skb);
        }
@@ -1645,6 +1647,11 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, 
bool zerocopy_success)
                napi_schedule(&vif->napi);
        } while (ubuf);
        spin_unlock_irqrestore(&vif->dealloc_lock, flags);
+
+       if (likely(zerocopy_success))
+               vif->tx_zerocopy_success++;
+       else
+               vif->tx_zerocopy_fail++;
 }
 
 static inline void xenvif_tx_action_dealloc(struct xenvif *vif)

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