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Subject[PATCH net-next,1/2] hv_netvsc: Fix the queue index computation in forwarding case
Date
From: Haiyang Zhang <haiyangz@microsoft.com>

If the outgoing skb has a RX queue mapping available, we use the queue
number directly, other than put it through Send Indirection Table.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Stephen Hemminger <sthemmin@microsoft.com>
---
drivers/net/hyperv/hyperv_net.h | 2 +-
drivers/net/hyperv/netvsc_drv.c | 46 ++++++++++++++++++++++++++------------
2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 4747ad4..768b3ae 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -633,7 +633,7 @@ struct nvsp_message {

#define NETVSC_PACKET_SIZE 4096

-#define VRSS_SEND_TAB_SIZE 16
+#define VRSS_SEND_TAB_SIZE 16 /* must be power of 2 */
#define VRSS_CHANNEL_MAX 64
#define VRSS_CHANNEL_DEFAULT 8

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index f24c289..e813eaf 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -191,6 +191,24 @@ static int netvsc_close(struct net_device *net)
return ppi;
}

+static inline int netvsc_get_tx_queue(struct net_device *ndev,
+ struct sk_buff *skb, int old_idx)
+{
+ const struct net_device_context *ndc = netdev_priv(ndev);
+ struct sock *sk = skb->sk;
+ int q_idx;
+
+ q_idx = ndc->tx_send_table[skb_get_hash(skb) &
+ (VRSS_SEND_TAB_SIZE - 1)];
+
+ /* If queue index changed record the new value */
+ if (q_idx != old_idx &&
+ sk && sk_fullsock(sk) && rcu_access_pointer(sk->sk_dst_cache))
+ sk_tx_queue_set(sk, q_idx);
+
+ return q_idx;
+}
+
/*
* Select queue for transmit.
*
@@ -205,24 +223,22 @@ static int netvsc_close(struct net_device *net)
static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
void *accel_priv, select_queue_fallback_t fallback)
{
- struct net_device_context *net_device_ctx = netdev_priv(ndev);
unsigned int num_tx_queues = ndev->real_num_tx_queues;
- struct sock *sk = skb->sk;
- int q_idx = sk_tx_queue_get(sk);
-
- if (q_idx < 0 || skb->ooo_okay || q_idx >= num_tx_queues) {
- u16 hash = __skb_tx_hash(ndev, skb, VRSS_SEND_TAB_SIZE);
- int new_idx;
-
- new_idx = net_device_ctx->tx_send_table[hash] % num_tx_queues;
+ int q_idx = sk_tx_queue_get(skb->sk);

- if (q_idx != new_idx && sk &&
- sk_fullsock(sk) && rcu_access_pointer(sk->sk_dst_cache))
- sk_tx_queue_set(sk, new_idx);
-
- q_idx = new_idx;
+ if (q_idx < 0 || skb->ooo_okay) {
+ /* If forwarding a packet, we use the recorded queue when
+ * available for better cache locality.
+ */
+ if (skb_rx_queue_recorded(skb))
+ q_idx = skb_get_rx_queue(skb);
+ else
+ q_idx = netvsc_get_tx_queue(ndev, skb, q_idx);
}

+ while (unlikely(q_idx >= num_tx_queues))
+ q_idx -= num_tx_queues;
+
return q_idx;
}

--
1.7.1
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