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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>
This commit is contained in:
Eric Dumazet 2012-01-04 14:18:38 +00:00 committed by David S. Miller
parent 23021c2105
commit 18cb809850
2 changed files with 123 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
include/linux/pkt_sched.h
View File

@ -162,19 +162,17 @@ struct tc_sfq_qopt {
unsigned flows; /* Maximal number of flows */
};
struct tc_sfq_qopt_v1 {
struct tc_sfq_qopt v0;
unsigned int depth; /* max number of packets per flow */
unsigned int headdrop;
};
struct tc_sfq_xstats {
__s32 allot;
};
/*
* NOTE: limit, divisor and flows are hardwired to code at the moment.
*
* limit=flows=128, divisor=1024;
*
* The only reason for this is efficiency, it is possible
* to change these parameters in compile time.
*/
/* RED section */
enum {

173
net/sched/sch_sfq.c
View File

@ -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;
struct tc_sfq_qopt_v1 opt;
opt.quantum = q->quantum;
opt.perturb_period = q->perturb_period / HZ;
opt.limit = q->limit;
opt.divisor = q->divisor;
opt.flows = q->limit;
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);