linux-kernel - [RFC PATCH 2/2] ptr_ring_ll: pop/push multiple objects at once

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Date:   Thu, 10 Nov 2016 20:44:32 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     jasowang@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/2] ptr_ring_ll: pop/push multiple objects at once

Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
---
 include/linux/ptr_ring_ll.h |   22 ++++++++++++++++------
 include/linux/skb_array.h   |   11 +++++++++--
 net/sched/sch_generic.c     |    2 +-
 3 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/include/linux/ptr_ring_ll.h b/include/linux/ptr_ring_ll.h
index bcb11f3..5dc25f7 100644
--- a/include/linux/ptr_ring_ll.h
+++ b/include/linux/ptr_ring_ll.h
@@ -45,9 +45,10 @@ struct ptr_ring_ll {
 /* Note: callers invoking this in a loop must use a compiler barrier,
  * for example cpu_relax(). Callers must hold producer_lock.
  */
-static inline int __ptr_ring_ll_produce(struct ptr_ring_ll *r, void *ptr)
+static inline int __ptr_ring_ll_produce_many(struct ptr_ring_ll *r,
+					     void **ptr, int num)
 {
-	u32 ret, head, tail, next, slots, mask;
+	u32 ret, head, tail, next, slots, mask, i;
 
 	do {
 		head = READ_ONCE(r->prod_head);
@@ -55,21 +56,30 @@ static inline int __ptr_ring_ll_produce(struct ptr_ring_ll *r, void *ptr)
 		tail = READ_ONCE(r->cons_tail);
 
 		slots = mask + tail - head;
-		if (slots < 1)
+		if (slots < num)
+			num = slots;
+
+		if (unlikely(!num))
 			return -ENOMEM;
 
-		next = head + 1;
+		next = head + num;
 		ret = cmpxchg(&r->prod_head, head, next);
 	} while (ret != head);
 
-	r->queue[head & mask] = ptr;
+	for (i = 0; i < num; i++)
+		r->queue[(head + i) & mask] = ptr[i];
 	smp_wmb();
 
 	while (r->prod_tail != head)
 		cpu_relax();
 
 	r->prod_tail = next;
-	return 0;
+	return num;
+}
+
+static inline int __ptr_ring_ll_produce(struct ptr_ring_ll *r, void **ptr)
+{
+	return __ptr_ring_ll_produce_many(r, ptr, 1);
 }
 
 static inline void *__ptr_ring_ll_consume(struct ptr_ring_ll *r)
diff --git a/include/linux/skb_array.h b/include/linux/skb_array.h
index 9b43dfd..de3c700 100644
--- a/include/linux/skb_array.h
+++ b/include/linux/skb_array.h
@@ -48,9 +48,16 @@ static inline bool skb_array_full(struct skb_array *a)
 	return ptr_ring_full(&a->ring);
 }
 
-static inline int skb_array_ll_produce(struct skb_array_ll *a, struct sk_buff *skb)
+static inline int skb_array_ll_produce_many(struct skb_array_ll *a,
+					    struct sk_buff **skb, int num)
 {
-	return __ptr_ring_ll_produce(&a->ring, skb);
+	return __ptr_ring_ll_produce_many(&a->ring, (void **)skb, num);
+}
+
+static inline int skb_array_ll_produce(struct skb_array_ll *a,
+				       struct sk_buff **skb)
+{
+	return __ptr_ring_ll_produce(&a->ring, (void **)skb);
 }
 
 static inline int skb_array_produce(struct skb_array *a, struct sk_buff *skb)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 4648ec8..58f2011 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -571,7 +571,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
 	struct skb_array_ll *q = band2list(priv, band);
 	int err;
 
-	err = skb_array_ll_produce(q, skb);
+	err = skb_array_ll_produce(q, &skb);
 
 	if (unlikely(err)) {
 		net_warn_ratelimited("drop a packet from fast enqueue\n");