ionic: Shorten a Tx hotpath

Perf was showing some hot spots in ionic_tx_descs_needed()
for TSO traffic.  Rework the function to return sooner where
possible.

Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index dcaa8a4d6ad501567b1c6d6e5df9651980f8e08c..2837f2cc01515750cc5b3c1c1bcf31bd0ccd0c10 100644 (file)
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -1669,7 +1669,7 @@ static int ionic_tx(struct ionic_queue *q, struct sk_buff *skb)
 
 static int ionic_tx_descs_needed(struct ionic_queue *q, struct sk_buff *skb)
 {
-       struct ionic_tx_stats *stats = q_to_tx_stats(q);
+       int nr_frags = skb_shinfo(skb)->nr_frags;
        bool too_many_frags = false;
        skb_frag_t *frag;
        int desc_bufs;
@@ -1685,17 +1685,20 @@ static int ionic_tx_descs_needed(struct ionic_queue *q, struct sk_buff *skb)
        /* Each desc is mss long max, so a descriptor for each gso_seg */
        if (skb_is_gso(skb)) {
                ndescs = skb_shinfo(skb)->gso_segs;
+               if (!nr_frags)
+                       return ndescs;
        } else {
                ndescs = 1;
-               if (skb_shinfo(skb)->nr_frags > q->max_sg_elems) {
+               if (!nr_frags)
+                       return ndescs;
+
+               if (unlikely(nr_frags > q->max_sg_elems)) {
                        too_many_frags = true;
                        goto linearize;
                }
-       }
 
-       /* If non-TSO, or no frags to check, we're done */
-       if (!skb_is_gso(skb) || !skb_shinfo(skb)->nr_frags)
                return ndescs;
+       }
 
        /* We need to scan the skb to be sure that none of the MTU sized
         * packets in the TSO will require more sgs per descriptor than we
@@ -1743,6 +1746,8 @@ static int ionic_tx_descs_needed(struct ionic_queue *q, struct sk_buff *skb)
 
 linearize:
        if (too_many_frags) {
+               struct ionic_tx_stats *stats = q_to_tx_stats(q);
+
                err = skb_linearize(skb);
                if (err)
                        return err;