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Date: Fri, 14 Aug 2009 18:55:20 +0530
From: Krishna Kumar <krkumar2@...ibm.com>
To: Jarek Poplawski <jarkao2@...il.com>
Cc: netdev@...r.kernel.org, herbert@...dor.apana.org.au,
kaber@...sh.net, Krishna Kumar <krkumar2@...ibm.com>,
davem@...emloft.net
Subject: [PATCH v1] Speed-up pfifo_fast lookup using a public bitmap
Signed-off-by: Krishna Kumar <krkumar2@...ibm.com>
---
include/net/sch_generic.h | 1
net/sched/sch_generic.c | 46 +++++++++++++++++++++++-------------
2 files changed, 31 insertions(+), 16 deletions(-)
diff -ruNp org/include/net/sch_generic.h new/include/net/sch_generic.h
--- org/include/net/sch_generic.h 2009-08-07 12:05:43.000000000 +0530
+++ new/include/net/sch_generic.h 2009-08-13 16:55:32.000000000 +0530
@@ -72,6 +72,7 @@ struct Qdisc
* For performance sake on SMP, we put highly modified fields at the end
*/
unsigned long state;
+ u32 bitmap;
struct sk_buff_head q;
struct gnet_stats_basic bstats;
struct gnet_stats_queue qstats;
diff -ruNp org/net/sched/sch_generic.c new/net/sched/sch_generic.c
--- org/net/sched/sch_generic.c 2009-08-07 12:05:43.000000000 +0530
+++ new/net/sched/sch_generic.c 2009-08-14 18:23:01.000000000 +0530
@@ -406,18 +406,28 @@ static const u8 prio2band[TC_PRIO_MAX+1]
#define PFIFO_FAST_BANDS 3
-static inline struct sk_buff_head *prio2list(struct sk_buff *skb,
- struct Qdisc *qdisc)
+/*
+ * Convert a bitmap to the first band number where an skb is queued, where:
+ * bitmap=0 means there are no skbs on any band.
+ * bitmap=1 means there is an skb on band 0.
+ * bitmap=7 means there are skbs on all 3 bands, etc.
+ */
+static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0};
+
+static inline struct sk_buff_head *band2list(struct Qdisc *qdisc, int band)
{
struct sk_buff_head *list = qdisc_priv(qdisc);
- return list + prio2band[skb->priority & TC_PRIO_MAX];
+
+ return list + band;
}
static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc* qdisc)
{
- struct sk_buff_head *list = prio2list(skb, qdisc);
+ int band = prio2band[skb->priority & TC_PRIO_MAX];
+ struct sk_buff_head *list = band2list(qdisc, band);
if (skb_queue_len(list) < qdisc_dev(qdisc)->tx_queue_len) {
+ qdisc->bitmap |= (1 << band);
qdisc->q.qlen++;
return __qdisc_enqueue_tail(skb, qdisc, list);
}
@@ -427,14 +437,17 @@ static int pfifo_fast_enqueue(struct sk_
static struct sk_buff *pfifo_fast_dequeue(struct Qdisc* qdisc)
{
- int prio;
- struct sk_buff_head *list = qdisc_priv(qdisc);
+ int band = bitmap2band[qdisc->bitmap];
- for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
- if (!skb_queue_empty(list + prio)) {
- qdisc->q.qlen--;
- return __qdisc_dequeue_head(qdisc, list + prio);
- }
+ if (likely(band >= 0)) {
+ struct sk_buff_head *list = qdisc_priv(qdisc);
+ struct sk_buff *skb = __qdisc_dequeue_head(qdisc, list + band);
+
+ qdisc->q.qlen--;
+ if (skb_queue_empty(list + band))
+ qdisc->bitmap &= ~(1 << band);
+
+ return skb;
}
return NULL;
@@ -442,12 +455,12 @@ static struct sk_buff *pfifo_fast_dequeu
static struct sk_buff *pfifo_fast_peek(struct Qdisc* qdisc)
{
- int prio;
- struct sk_buff_head *list = qdisc_priv(qdisc);
+ int band = bitmap2band[qdisc->bitmap];
+
+ if (band >= 0) {
+ struct sk_buff_head *list = qdisc_priv(qdisc);
- for (prio = 0; prio < PFIFO_FAST_BANDS; prio++) {
- if (!skb_queue_empty(list + prio))
- return skb_peek(list + prio);
+ return skb_peek(list + band);
}
return NULL;
@@ -461,6 +474,7 @@ static void pfifo_fast_reset(struct Qdis
for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
__qdisc_reset_queue(qdisc, list + prio);
+ qdisc->bitmap = 0;
qdisc->qstats.backlog = 0;
qdisc->q.qlen = 0;
}
--
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