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>

1 files changed, 19 insertions, 7 deletions

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 6a2f88fea6d8..b76d46b71466 100644
--- 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);