From 808e7ac0bdef31204184904f6b3ea356a30a9ed5 Mon Sep 17 00:00:00 2001
From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Wed, 1 Oct 2014 22:36:09 +0200
Subject: [PATCH] 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>
---
net/sched/sch_generic.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index c2e87e63b8326..797ebef736421 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;
}
--
2.30.2