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Date: Fri, 14 Jan 2011 04:58:18 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Stephen Hemminger <shemminger@...tta.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] CHOKe flow scheduler (0.8)
Le vendredi 14 janvier 2011 à 04:34 +0100, Eric Dumazet a écrit :
> Hmm, please wait a bit, I had another crash when I stopped my
> bench/stress
I am not sure p->qavg is correctly computed.
Crash happened because choke_peek_random() was called while no packet
was in queue.
With my params (min=10833 max=32500 burst=18055 limit=130000) this
implies qavg was very big while qlen==0 !
qdisc choke 11: dev ifb0 parent 1:11 limit 130000b min 10833b max 32500b ewma 13 Plog 21 Scell_log 30
Sent 200857857 bytes 365183 pkt (dropped 1010937, overlimits 557577 requeues 0)
rate 32253Kbit 7330pps backlog 17875996b 32505p requeues 0
marked 0 early 557577 pdrop 0 other 0 matched 226680
Here is latest diff :
include/linux/pkt_sched.h | 8 +++----
net/sched/sch_choke.c | 50 +++++++++++++++++++++++++++++-----------------
2 files changed, 36 insertions(+), 22 deletions(-)
diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 83bac92..498c798 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -269,10 +269,10 @@ struct tc_choke_qopt {
};
struct tc_choke_xstats {
- __u32 early; /* Early drops */
- __u32 pdrop; /* Drops due to queue limits */
- __u32 other; /* Drops due to drop() calls */
- __u32 marked; /* Marked packets */
+ __u32 early; /* Early drops */
+ __u32 pdrop; /* Drops due to queue limits */
+ __u32 other; /* Drops due to drop() calls */
+ __u32 marked; /* Marked packets */
__u32 matched; /* Drops due to flow match */
};
diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index 136d4e5..2f94dad 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -74,7 +74,7 @@ struct choke_sched_data {
};
/* deliver a random number between 0 and N - 1 */
-static inline u32 random_N(unsigned int N)
+static u32 random_N(unsigned int N)
{
return reciprocal_divide(random32(), N);
}
@@ -94,18 +94,20 @@ static struct sk_buff *choke_peek_random(struct Qdisc *sch,
return skb;
} while (--retrys > 0);
- /* queue is has lots of holes use the head which is known to exist */
+ /* queue is has lots of holes use the head which is known to exist
+ * Note : result can still be NULL if q->head == q->tail
+ */
return q->tab[*pidx = q->head];
}
/* Is ECN parameter configured */
-static inline int use_ecn(const struct choke_sched_data *q)
+static int use_ecn(const struct choke_sched_data *q)
{
return q->flags & TC_RED_ECN;
}
/* Should packets over max just be dropped (versus marked) */
-static inline int use_harddrop(const struct choke_sched_data *q)
+static int use_harddrop(const struct choke_sched_data *q)
{
return q->flags & TC_RED_HARDDROP;
}
@@ -113,20 +115,21 @@ static inline int use_harddrop(const struct choke_sched_data *q)
/* Move head pointer forward to skip over holes */
static void choke_zap_head_holes(struct choke_sched_data *q)
{
- while (q->tab[q->head] == NULL) {
+ do {
q->head = (q->head + 1) & q->tab_mask;
-
- BUG_ON(q->head == q->tail);
- }
+ if (q->head == q->tail)
+ break;
+ } while (q->tab[q->head] == NULL);
}
/* Move tail pointer backwards to reuse holes */
static void choke_zap_tail_holes(struct choke_sched_data *q)
{
- while (q->tab[q->tail - 1] == NULL) {
+ do {
q->tail = (q->tail - 1) & q->tab_mask;
- BUG_ON(q->head == q->tail);
- }
+ if (q->head == q->tail)
+ break;
+ } while (q->tab[q->tail] == NULL);
}
/* Drop packet from queue array by creating a "hole" */
@@ -145,7 +148,7 @@ static void choke_drop_by_idx(struct choke_sched_data *q, unsigned int idx)
2. fast internal classification
3. use TC filter based classification
*/
-static inline unsigned int choke_classify(struct sk_buff *skb,
+static unsigned int choke_classify(struct sk_buff *skb,
struct Qdisc *sch, int *qerr)
{
@@ -214,11 +217,12 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
oskb = choke_peek_random(sch, &idx);
/* Both packets from same flow ? */
- if (*(unsigned int *)(qdisc_skb_cb(oskb)->data) == hash) {
+ if (oskb &&
+ *(unsigned int *)(qdisc_skb_cb(oskb)->data) == hash) {
/* Drop both packets */
q->stats.matched++;
choke_drop_by_idx(q, idx);
- sch->qstats.backlog -= qdisc_pkt_len(skb);
+ sch->qstats.backlog -= qdisc_pkt_len(oskb);
--sch->q.qlen;
qdisc_drop(oskb, sch);
goto congestion_drop;
@@ -285,8 +289,7 @@ static struct sk_buff *choke_dequeue(struct Qdisc *sch)
}
skb = q->tab[q->head];
- q->tab[q->head] = NULL; /* not really needed */
- q->head = (q->head + 1) & q->tab_mask;
+ q->tab[q->head] = NULL;
choke_zap_head_holes(q);
--sch->q.qlen;
sch->qstats.backlog -= qdisc_pkt_len(skb);
@@ -371,12 +374,23 @@ static int choke_change(struct Qdisc *sch, struct nlattr *opt)
sch_tree_lock(sch);
old = q->tab;
if (old) {
- unsigned int tail = 0;
+ unsigned int oqlen = sch->q.qlen, tail = 0;
while (q->head != q->tail) {
- ntab[tail++] = q->tab[q->head];
+ struct sk_buff *skb = q->tab[q->head];
+
q->head = (q->head + 1) & q->tab_mask;
+ if (!skb)
+ continue;
+ if (tail < mask) {
+ ntab[tail++] = skb;
+ continue;
+ }
+ sch->qstats.backlog -= qdisc_pkt_len(skb);
+ --sch->q.qlen;
+ qdisc_drop(skb, sch);
}
+ qdisc_tree_decrease_qlen(sch, oqlen - sch->q.qlen);
q->head = 0;
q->tail = tail;
}
--
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