sch_sfq: allow big packets and be fair

SFQ is currently 'limited' to small packets, because it uses a 15bit
allotment number per flow. Introduce a scale by 8, so that we can handle
full size TSO/GRO packets.

Use appropriate handling to make sure allot is positive before a new
packet is dequeued, so that fairness is respected.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Jarek Poplawski <jarkao2@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 6a2f88fea6d8f8fbb1b791c53a74287fd7680727..b76d46b71466193178c61f25c10ce0eb4d21bf5d 100644 (file)
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -67,7 +67,7 @@
 
        IMPLEMENTATION:
        This implementation limits maximal queue length to 128;
-       maximal mtu to 2^15-1; max 128 flows, number of hash buckets to 1024.
+       max mtu to 2^18-1; max 128 flows, number of hash buckets to 1024.
        The only goal of this restrictions was that all data
        fit into one 4K page on 32bit arches.
 
@@ -77,6 +77,11 @@
 #define SFQ_SLOTS              128 /* max number of flows */
 #define SFQ_EMPTY_SLOT         255
 #define SFQ_HASH_DIVISOR       1024
+/* We use 16 bits to store allot, and want to handle packets up to 64K
+ * Scale allot by 8 (1<<3) so that no overflow occurs.
+ */
+#define SFQ_ALLOT_SHIFT                3
+#define SFQ_ALLOT_SIZE(X)      DIV_ROUND_UP(X, 1 << SFQ_ALLOT_SHIFT)
 
 /* This type should contain at least SFQ_DEPTH + SFQ_SLOTS values */
 typedef unsigned char sfq_index;
@@ -115,7 +120,7 @@ struct sfq_sched_data
        struct timer_list perturb_timer;
        u32             perturbation;
        sfq_index       cur_depth;      /* depth of longest slot */
-
+       unsigned short  scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
        struct sfq_slot *tail;          /* current slot in round */
        sfq_index       ht[SFQ_HASH_DIVISOR];   /* Hash table */
        struct sfq_slot slots[SFQ_SLOTS];
@@ -395,7 +400,7 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
                        q->tail->next = x;
                }
                q->tail = slot;
-               slot->allot = q->quantum;
+               slot->allot = q->scaled_quantum;
        }
        if (++sch->q.qlen <= q->limit) {
                sch->bstats.bytes += qdisc_pkt_len(skb);
@@ -431,8 +436,14 @@ sfq_dequeue(struct Qdisc *sch)
        if (q->tail == NULL)
                return NULL;
 
+next_slot:
        a = q->tail->next;
        slot = &q->slots[a];
+       if (slot->allot <= 0) {
+               q->tail = slot;
+               slot->allot += q->scaled_quantum;
+               goto next_slot;
+       }
        skb = slot_dequeue_head(slot);
        sfq_dec(q, a);
        sch->q.qlen--;
@@ -447,9 +458,8 @@ sfq_dequeue(struct Qdisc *sch)
                        return skb;
                }
                q->tail->next = next_a;
-       } else if ((slot->allot -= qdisc_pkt_len(skb)) <= 0) {
-               q->tail = slot;
-               slot->allot += q->quantum;
+       } else {
+               slot->allot -= SFQ_ALLOT_SIZE(qdisc_pkt_len(skb));
        }
        return skb;
 }
@@ -485,6 +495,7 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
 
        sch_tree_lock(sch);
        q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
+       q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
        q->perturb_period = ctl->perturb_period * HZ;
        if (ctl->limit)
                q->limit = min_t(u32, ctl->limit, SFQ_DEPTH - 1);
@@ -525,6 +536,7 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
        q->tail = NULL;
        if (opt == NULL) {
                q->quantum = psched_mtu(qdisc_dev(sch));
+               q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
                q->perturb_period = 0;
                q->perturbation = net_random();
        } else {
@@ -617,7 +629,7 @@ static int sfq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
        if (idx != SFQ_EMPTY_SLOT) {
                const struct sfq_slot *slot = &q->slots[idx];
 
-               xstats.allot = slot->allot;
+               xstats.allot = slot->allot << SFQ_ALLOT_SHIFT;
                qs.qlen = slot->qlen;
                slot_queue_walk(slot, skb)
                        qs.backlog += qdisc_pkt_len(skb);