qdisc: dequeue bulking also pickup GSO/TSO packets

The TSO and GSO segmented packets already benefit from bulking
on their own.

The TSO packets have always taken advantage of the only updating
the tailptr once for a large packet.

The GSO segmented packets have recently taken advantage of
bulking xmit_more API, via merge commit 53fda7f7f9e8 ("Merge
branch 'xmit_list'"), specifically via commit 7f2e870f2a4 ("net:
Move main gso loop out of dev_hard_start_xmit() into helper.")
allowing qdisc requeue of remaining list.  And via commit
ce93718fb7cd ("net: Don't keep around original SKB when we
software segment GSO frames.").

This patch allow further bulking of TSO/GSO packets together,
when dequeueing from the qdisc.

Testing:
 Measuring HoL (Head-of-Line) blocking for TSO and GSO, with
netperf-wrapper. Bulking several TSO show no performance regressions
(requeues were in the area 32 requeues/sec).

Bulking several GSOs does show small regression or very small
improvement (requeues were in the area 8000 requeues/sec).

 Using ixgbe 10Gbit/s with GSO bulking, we can measure some additional
latency. Base-case, which is "normal" GSO bulking, sees varying
high-prio queue delay between 0.38ms to 0.47ms.  Bulking several GSOs
together, result in a stable high-prio queue delay of 0.50ms.

 Using igb at 100Mbit/s with GSO bulking, shows an improvement.
Base-case sees varying high-prio queue delay between 2.23ms to 2.35ms

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 9 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index c2e87e63b832..797ebef73642 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -63,10 +63,6 @@ static struct sk_buff *try_bulk_dequeue_skb(struct Qdisc *q,
         struct sk_buff *skb, *tail_skb = head_skb;
 
         while (bytelimit > 0) {
-                /* For now, don't bulk dequeue GSO (or GSO segmented) pkts */
-                if (tail_skb->next || skb_is_gso(tail_skb))
-                        break;
-
                 skb = q->dequeue(q);
                 if (!skb)
                         break;
@@ -76,11 +72,9 @@ static struct sk_buff *try_bulk_dequeue_skb(struct Qdisc *q,
                 if (!skb)
                         break;
 
-                /* "skb" can be a skb list after validate call above
-                 * (GSO segmented), but it is okay to append it to
-                 * current tail_skb->next, because next round will exit
-                 * in-case "tail_skb->next" is a skb list.
-                 */
+                while (tail_skb->next) /* GSO list goto tail */
+                        tail_skb = tail_skb->next;
+
                 tail_skb->next = skb;
                 tail_skb = skb;
         }