net_sched: sfq: extend limits

SFQ as implemented in Linux is very limited, with at most 127 flows
and limit of 127 packets. [ So if 127 flows are active, we have one
packet per flow ]

This patch brings to SFQ following features to cope with modern needs.

- Ability to specify a smaller per flow limit of inflight packets.
    (default value being at 127 packets)

- Ability to have up to 65408 active flows (instead of 127)

- Ability to have head drops instead of tail drops
  (to drop old packets from a flow)

Example of use : No more than 20 packets per flow, max 8000 flows, max
20000 packets in SFQ qdisc, hash table of 65536 slots.

tc qdisc add ... sfq \
        flows 8000 \
        depth 20 \
        headdrop \
        limit 20000 \
	divisor 65536

Ram usage :

2 bytes per hash table entry (instead of previous 1 byte/entry)
32 bytes per flow on 64bit arches, instead of 384 for QFQ, so much
better cache hit ratio.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Dave Taht <dave.taht@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 117 insertions, 58 deletions

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 843018154a5c..0a7964009e8c 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -66,16 +66,18 @@
         SFQ is superior for this purpose.
 
         IMPLEMENTATION:
-        This implementation limits maximal queue length to 128;
-        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.
+        This implementation limits :
+        - maximal queue length per flow to 127 packets.
+        - max mtu to 2^18-1;
+        - max 65408 flows,
+        - number of hash buckets to 65536.
 
         It is easy to increase these values, but not in flight.  */
 
-#define SFQ_DEPTH               128 /* max number of packets per flow */
-#define SFQ_SLOTS               128 /* max number of flows */
-#define SFQ_EMPTY_SLOT          255
+#define SFQ_MAX_DEPTH           127 /* max number of packets per flow */
+#define SFQ_DEFAULT_FLOWS       128
+#define SFQ_MAX_FLOWS           (0x10000 - SFQ_MAX_DEPTH - 1) /* max number of flows */
+#define SFQ_EMPTY_SLOT          0xffff
 #define SFQ_DEFAULT_HASH_DIVISOR 1024
 
 /* We use 16 bits to store allot, and want to handle packets up to 64K
@@ -84,13 +86,13 @@
 #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;
+/* This type should contain at least SFQ_MAX_DEPTH + 1 + SFQ_MAX_FLOWS values */
+typedef u16 sfq_index;
 
 /*
  * We dont use pointers to save space.
- * Small indexes [0 ... SFQ_SLOTS - 1] are 'pointers' to slots[] array
- * while following values [SFQ_SLOTS ... SFQ_SLOTS + SFQ_DEPTH - 1]
+ * Small indexes [0 ... SFQ_MAX_FLOWS - 1] are 'pointers' to slots[] array
+ * while following values [SFQ_MAX_FLOWS ... SFQ_MAX_FLOWS + SFQ_MAX_DEPTH]
  * are 'pointers' to dep[] array
  */
 struct sfq_head {
@@ -102,28 +104,38 @@ struct sfq_slot {
         struct sk_buff  *skblist_next;
         struct sk_buff  *skblist_prev;
         sfq_index       qlen; /* number of skbs in skblist */
-        sfq_index       next; /* next slot in sfq chain */
+        sfq_index       next; /* next slot in sfq RR chain */
         struct sfq_head dep; /* anchor in dep[] chains */
         unsigned short  hash; /* hash value (index in ht[]) */
         short           allot; /* credit for this slot */
 };
 
 struct sfq_sched_data {
-/* Parameters */
-        int             perturb_period;
-        unsigned int    quantum;        /* Allotment per round: MUST BE >= MTU */
-        int             limit;
+/* frequently used fields */
+        int             limit;          /* limit of total number of packets in this qdisc */
         unsigned int    divisor;        /* number of slots in hash table */
-/* Variables */
-        struct tcf_proto *filter_list;
-        struct timer_list perturb_timer;
+        unsigned int    maxflows;       /* number of flows in flows array */
+        int             headdrop;
+        int             maxdepth;       /* limit of packets per flow */
+
         u32             perturbation;
+        struct tcf_proto *filter_list;
         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;            /* Hash table (divisor slots) */
-        struct sfq_slot slots[SFQ_SLOTS];
-        struct sfq_head dep[SFQ_DEPTH]; /* Linked list of slots, indexed by depth */
+        sfq_index       *ht;            /* Hash table ('divisor' slots) */
+        struct sfq_slot *slots;         /* Flows table ('maxflows' entries) */
+
+        struct sfq_head dep[SFQ_MAX_DEPTH + 1];
+                                        /* Linked lists of slots, indexed by depth
+                                         * dep[0] : list of unused flows
+                                         * dep[1] : list of flows with 1 packet
+                                         * dep[X] : list of flows with X packets
+                                         */
+
+        int             perturb_period;
+        unsigned int    quantum;        /* Allotment per round: MUST BE >= MTU */
+        struct timer_list perturb_timer;
 };
 
 /*
@@ -131,9 +143,9 @@ struct sfq_sched_data {
  */
 static inline struct sfq_head *sfq_dep_head(struct sfq_sched_data *q, sfq_index val)
 {
-        if (val < SFQ_SLOTS)
+        if (val < SFQ_MAX_FLOWS)
                 return &q->slots[val].dep;
-        return &q->dep[val - SFQ_SLOTS];
+        return &q->dep[val - SFQ_MAX_FLOWS];
 }
 
 /*
@@ -199,18 +211,19 @@ static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
 }
 
 /*
- * x : slot number [0 .. SFQ_SLOTS - 1]
+ * x : slot number [0 .. SFQ_MAX_FLOWS - 1]
  */
 static inline void sfq_link(struct sfq_sched_data *q, sfq_index x)
 {
         sfq_index p, n;
-        int qlen = q->slots[x].qlen;
+        struct sfq_slot *slot = &q->slots[x];
+        int qlen = slot->qlen;
 
-        p = qlen + SFQ_SLOTS;
+        p = qlen + SFQ_MAX_FLOWS;
         n = q->dep[qlen].next;
 
-        q->slots[x].dep.next = n;
-        q->slots[x].dep.prev = p;
+        slot->dep.next = n;
+        slot->dep.prev = p;
 
         q->dep[qlen].next = x;          /* sfq_dep_head(q, p)->next = x */
         sfq_dep_head(q, n)->prev = x;
@@ -275,6 +288,7 @@ static inline struct sk_buff *slot_dequeue_head(struct sfq_slot *slot)
 
 static inline void slot_queue_init(struct sfq_slot *slot)
 {
+        memset(slot, 0, sizeof(*slot));
         slot->skblist_prev = slot->skblist_next = (struct sk_buff *)slot;
 }
 
@@ -305,7 +319,7 @@ static unsigned int sfq_drop(struct Qdisc *sch)
                 x = q->dep[d].next;
                 slot = &q->slots[x];
 drop:
-                skb = slot_dequeue_tail(slot);
+                skb = q->headdrop ? slot_dequeue_head(slot) : slot_dequeue_tail(slot);
                 len = qdisc_pkt_len(skb);
                 sfq_dec(q, x);
                 kfree_skb(skb);
@@ -349,16 +363,27 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
         slot = &q->slots[x];
         if (x == SFQ_EMPTY_SLOT) {
                 x = q->dep[0].next; /* get a free slot */
+                if (x >= SFQ_MAX_FLOWS)
+                        return qdisc_drop(skb, sch);
                 q->ht[hash] = x;
                 slot = &q->slots[x];
                 slot->hash = hash;
         }
 
-        /* If selected queue has length q->limit, do simple tail drop,
-         * i.e. drop _this_ packet.
-         */
-        if (slot->qlen >= q->limit)
-                return qdisc_drop(skb, sch);
+        if (slot->qlen >= q->maxdepth) {
+                struct sk_buff *head;
+
+                if (!q->headdrop)
+                        return qdisc_drop(skb, sch);
+
+                head = slot_dequeue_head(slot);
+                sch->qstats.backlog -= qdisc_pkt_len(head);
+                qdisc_drop(head, sch);
+
+                sch->qstats.backlog += qdisc_pkt_len(skb);
+                slot_queue_add(slot, skb);
+                return NET_XMIT_CN;
+        }
 
         sch->qstats.backlog += qdisc_pkt_len(skb);
         slot_queue_add(slot, skb);
@@ -445,16 +470,18 @@ sfq_reset(struct Qdisc *sch)
  * We dont use sfq_dequeue()/sfq_enqueue() because we dont want to change
  * counters.
  */
-static void sfq_rehash(struct sfq_sched_data *q)
+static void sfq_rehash(struct Qdisc *sch)
 {
+        struct sfq_sched_data *q = qdisc_priv(sch);
         struct sk_buff *skb;
         int i;
         struct sfq_slot *slot;
         struct sk_buff_head list;
+        int dropped = 0;
 
         __skb_queue_head_init(&list);
 
-        for (i = 0; i < SFQ_SLOTS; i++) {
+        for (i = 0; i < q->maxflows; i++) {
                 slot = &q->slots[i];
                 if (!slot->qlen)
                         continue;
@@ -474,10 +501,18 @@ static void sfq_rehash(struct sfq_sched_data *q)
                 slot = &q->slots[x];
                 if (x == SFQ_EMPTY_SLOT) {
                         x = q->dep[0].next; /* get a free slot */
+                        if (x >= SFQ_MAX_FLOWS) {
+drop:                           sch->qstats.backlog -= qdisc_pkt_len(skb);
+                                kfree_skb(skb);
+                                dropped++;
+                                continue;
+                        }
                         q->ht[hash] = x;
                         slot = &q->slots[x];
                         slot->hash = hash;
                 }
+                if (slot->qlen >= q->maxdepth)
+                        goto drop;
                 slot_queue_add(slot, skb);
                 sfq_inc(q, x);
                 if (slot->qlen == 1) {          /* The flow is new */
@@ -491,6 +526,8 @@ static void sfq_rehash(struct sfq_sched_data *q)
                         slot->allot = q->scaled_quantum;
                 }
         }
+        sch->q.qlen -= dropped;
+        qdisc_tree_decrease_qlen(sch, dropped);
 }
 
 static void sfq_perturbation(unsigned long arg)
@@ -502,7 +539,7 @@ static void sfq_perturbation(unsigned long arg)
         spin_lock(root_lock);
         q->perturbation = net_random();
         if (!q->filter_list && q->tail)
-                sfq_rehash(q);
+                sfq_rehash(sch);
         spin_unlock(root_lock);
 
         if (q->perturb_period)
@@ -513,23 +550,39 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
 {
         struct sfq_sched_data *q = qdisc_priv(sch);
         struct tc_sfq_qopt *ctl = nla_data(opt);
+        struct tc_sfq_qopt_v1 *ctl_v1 = NULL;
         unsigned int qlen;
 
         if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
                 return -EINVAL;
-
+        if (opt->nla_len >= nla_attr_size(sizeof(*ctl_v1)))
+                ctl_v1 = nla_data(opt);
         if (ctl->divisor &&
             (!is_power_of_2(ctl->divisor) || ctl->divisor > 65536))
                 return -EINVAL;
 
         sch_tree_lock(sch);
-        q->quantum = ctl->quantum ? : psched_mtu(qdisc_dev(sch));
-        q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
+        if (ctl->quantum) {
+                q->quantum = ctl->quantum;
+                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);
-        if (ctl->divisor)
+        if (ctl->flows)
+                q->maxflows = min_t(u32, ctl->flows, SFQ_MAX_FLOWS);
+        if (ctl->divisor) {
                 q->divisor = ctl->divisor;
+                q->maxflows = min_t(u32, q->maxflows, q->divisor);
+        }
+        if (ctl_v1) {
+                if (ctl_v1->depth)
+                        q->maxdepth = min_t(u32, ctl_v1->depth, SFQ_MAX_DEPTH);
+                q->headdrop = ctl_v1->headdrop;
+        }
+        if (ctl->limit) {
+                q->limit = min_t(u32, ctl->limit, q->maxdepth * q->maxflows);
+                q->maxflows = min_t(u32, q->maxflows, q->limit);
+        }
+
         qlen = sch->q.qlen;
         while (sch->q.qlen > q->limit)
                 sfq_drop(sch);
@@ -571,6 +624,7 @@ static void sfq_destroy(struct Qdisc *sch)
         q->perturb_period = 0;
         del_timer_sync(&q->perturb_timer);
         sfq_free(q->ht);
+        sfq_free(q->slots);
 }
 
 static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
@@ -582,15 +636,17 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
         q->perturb_timer.data = (unsigned long)sch;
         init_timer_deferrable(&q->perturb_timer);
 
-        for (i = 0; i < SFQ_DEPTH; i++) {
-                q->dep[i].next = i + SFQ_SLOTS;
-                q->dep[i].prev = i + SFQ_SLOTS;
+        for (i = 0; i < SFQ_MAX_DEPTH + 1; i++) {
+                q->dep[i].next = i + SFQ_MAX_FLOWS;
+                q->dep[i].prev = i + SFQ_MAX_FLOWS;
         }
 
-        q->limit = SFQ_DEPTH - 1;
+        q->limit = SFQ_MAX_DEPTH;
+        q->maxdepth = SFQ_MAX_DEPTH;
         q->cur_depth = 0;
         q->tail = NULL;
         q->divisor = SFQ_DEFAULT_HASH_DIVISOR;
+        q->maxflows = SFQ_DEFAULT_FLOWS;
         q->quantum = psched_mtu(qdisc_dev(sch));
         q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
         q->perturb_period = 0;
@@ -603,14 +659,15 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt)
         }
 
         q->ht = sfq_alloc(sizeof(q->ht[0]) * q->divisor);
-        if (!q->ht) {
+        q->slots = sfq_alloc(sizeof(q->slots[0]) * q->maxflows);
+        if (!q->ht || !q->slots) {
                 sfq_destroy(sch);
                 return -ENOMEM;
         }
         for (i = 0; i < q->divisor; i++)
                 q->ht[i] = SFQ_EMPTY_SLOT;
 
-        for (i = 0; i < SFQ_SLOTS; i++) {
+        for (i = 0; i < q->maxflows; i++) {
                 slot_queue_init(&q->slots[i]);
                 sfq_link(q, i);
         }
@@ -625,14 +682,16 @@ static int sfq_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
         struct sfq_sched_data *q = qdisc_priv(sch);
         unsigned char *b = skb_tail_pointer(skb);
-        struct tc_sfq_qopt opt;
-
-        opt.quantum = q->quantum;
-        opt.perturb_period = q->perturb_period / HZ;
-
-        opt.limit = q->limit;
-        opt.divisor = q->divisor;
-        opt.flows = q->limit;
+        struct tc_sfq_qopt_v1 opt;
+
+        memset(&opt, 0, sizeof(opt));
+        opt.v0.quantum  = q->quantum;
+        opt.v0.perturb_period = q->perturb_period / HZ;
+        opt.v0.limit    = q->limit;
+        opt.v0.divisor  = q->divisor;
+        opt.v0.flows    = q->maxflows;
+        opt.depth       = q->maxdepth;
+        opt.headdrop    = q->headdrop;
 
         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);