Release 4.11 net/sched/sch_fq.c
/*
* net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
*
* Copyright (C) 2013-2015 Eric Dumazet <edumazet@google.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Meant to be mostly used for locally generated traffic :
* Fast classification depends on skb->sk being set before reaching us.
* If not, (router workload), we use rxhash as fallback, with 32 bits wide hash.
* All packets belonging to a socket are considered as a 'flow'.
*
* Flows are dynamically allocated and stored in a hash table of RB trees
* They are also part of one Round Robin 'queues' (new or old flows)
*
* Burst avoidance (aka pacing) capability :
*
* Transport (eg TCP) can set in sk->sk_pacing_rate a rate, enqueue a
* bunch of packets, and this packet scheduler adds delay between
* packets to respect rate limitation.
*
* enqueue() :
* - lookup one RB tree (out of 1024 or more) to find the flow.
* If non existent flow, create it, add it to the tree.
* Add skb to the per flow list of skb (fifo).
* - Use a special fifo for high prio packets
*
* dequeue() : serves flows in Round Robin
* Note : When a flow becomes empty, we do not immediately remove it from
* rb trees, for performance reasons (its expected to send additional packets,
* or SLAB cache will reuse socket for another flow)
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/string.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
#include <linux/hash.h>
#include <linux/prefetch.h>
#include <linux/vmalloc.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/tcp.h>
/*
* Per flow structure, dynamically allocated
*/
struct fq_flow {
struct sk_buff *head; /* list of skbs for this flow : first skb */
union {
struct sk_buff *tail; /* last skb in the list */
unsigned long age; /* jiffies when flow was emptied, for gc */
};
struct rb_node fq_node; /* anchor in fq_root[] trees */
struct sock *sk;
int qlen; /* number of packets in flow queue */
int credit;
u32 socket_hash; /* sk_hash */
struct fq_flow *next; /* next pointer in RR lists, or &detached */
struct rb_node rate_node; /* anchor in q->delayed tree */
u64 time_next_packet;
};
struct fq_flow_head {
struct fq_flow *first;
struct fq_flow *last;
};
struct fq_sched_data {
struct fq_flow_head new_flows;
struct fq_flow_head old_flows;
struct rb_root delayed; /* for rate limited flows */
u64 time_next_delayed_flow;
unsigned long unthrottle_latency_ns;
struct fq_flow internal; /* for non classified or high prio packets */
u32 quantum;
u32 initial_quantum;
u32 flow_refill_delay;
u32 flow_max_rate; /* optional max rate per flow */
u32 flow_plimit; /* max packets per flow */
u32 orphan_mask; /* mask for orphaned skb */
u32 low_rate_threshold;
struct rb_root *fq_root;
u8 rate_enable;
u8 fq_trees_log;
u32 flows;
u32 inactive_flows;
u32 throttled_flows;
u64 stat_gc_flows;
u64 stat_internal_packets;
u64 stat_tcp_retrans;
u64 stat_throttled;
u64 stat_flows_plimit;
u64 stat_pkts_too_long;
u64 stat_allocation_errors;
struct qdisc_watchdog watchdog;
};
/* special value to mark a detached flow (not on old/new list) */
static struct fq_flow detached, throttled;
static void fq_flow_set_detached(struct fq_flow *f)
{
f->next = &detached;
f->age = jiffies;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 24 | 100.00% | 2 | 100.00% |
Total | 24 | 100.00% | 2 | 100.00% |
static bool fq_flow_is_detached(const struct fq_flow *f)
{
return f->next == &detached;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 20 | 100.00% | 1 | 100.00% |
Total | 20 | 100.00% | 1 | 100.00% |
static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
{
struct rb_node **p = &q->delayed.rb_node, *parent = NULL;
while (*p) {
struct fq_flow *aux;
parent = *p;
aux = rb_entry(parent, struct fq_flow, rate_node);
if (f->time_next_packet >= aux->time_next_packet)
p = &parent->rb_right;
else
p = &parent->rb_left;
}
rb_link_node(&f->rate_node, parent, p);
rb_insert_color(&f->rate_node, &q->delayed);
q->throttled_flows++;
q->stat_throttled++;
f->next = &throttled;
if (q->time_next_delayed_flow > f->time_next_packet)
q->time_next_delayed_flow = f->time_next_packet;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 147 | 99.32% | 1 | 50.00% |
Geliang Tang | 1 | 0.68% | 1 | 50.00% |
Total | 148 | 100.00% | 2 | 100.00% |
static struct kmem_cache *fq_flow_cachep __read_mostly;
static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow)
{
if (head->first)
head->last->next = flow;
else
head->first = flow;
head->last = flow;
flow->next = NULL;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 49 | 100.00% | 1 | 100.00% |
Total | 49 | 100.00% | 1 | 100.00% |
/* limit number of collected flows per round */
#define FQ_GC_MAX 8
#define FQ_GC_AGE (3*HZ)
static bool fq_gc_candidate(const struct fq_flow *f)
{
return fq_flow_is_detached(f) &&
time_after(jiffies, f->age + FQ_GC_AGE);
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 29 | 100.00% | 1 | 100.00% |
Total | 29 | 100.00% | 1 | 100.00% |
static void fq_gc(struct fq_sched_data *q,
struct rb_root *root,
struct sock *sk)
{
struct fq_flow *f, *tofree[FQ_GC_MAX];
struct rb_node **p, *parent;
int fcnt = 0;
p = &root->rb_node;
parent = NULL;
while (*p) {
parent = *p;
f = rb_entry(parent, struct fq_flow, fq_node);
if (f->sk == sk)
break;
if (fq_gc_candidate(f)) {
tofree[fcnt++] = f;
if (fcnt == FQ_GC_MAX)
break;
}
if (f->sk > sk)
p = &parent->rb_right;
else
p = &parent->rb_left;
}
q->flows -= fcnt;
q->inactive_flows -= fcnt;
q->stat_gc_flows += fcnt;
while (fcnt) {
struct fq_flow *f = tofree[--fcnt];
rb_erase(&f->fq_node, root);
kmem_cache_free(fq_flow_cachep, f);
}
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 188 | 99.47% | 1 | 50.00% |
Geliang Tang | 1 | 0.53% | 1 | 50.00% |
Total | 189 | 100.00% | 2 | 100.00% |
static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
{
struct rb_node **p, *parent;
struct sock *sk = skb->sk;
struct rb_root *root;
struct fq_flow *f;
/* warning: no starvation prevention... */
if (unlikely((skb->priority & TC_PRIO_MAX) == TC_PRIO_CONTROL))
return &q->internal;
/* SYNACK messages are attached to a TCP_NEW_SYN_RECV request socket
* or a listener (SYNCOOKIE mode)
* 1) request sockets are not full blown,
* they do not contain sk_pacing_rate
* 2) They are not part of a 'flow' yet
* 3) We do not want to rate limit them (eg SYNFLOOD attack),
* especially if the listener set SO_MAX_PACING_RATE
* 4) We pretend they are orphaned
*/
if (!sk || sk_listener(sk)) {
unsigned long hash = skb_get_hash(skb) & q->orphan_mask;
/* By forcing low order bit to 1, we make sure to not
* collide with a local flow (socket pointers are word aligned)
*/
sk = (struct sock *)((hash << 1) | 1UL);
skb_orphan(skb);
}
root = &q->fq_root[hash_ptr(sk, q->fq_trees_log)];
if (q->flows >= (2U << q->fq_trees_log) &&
q->inactive_flows > q->flows/2)
fq_gc(q, root, sk);
p = &root->rb_node;
parent = NULL;
while (*p) {
parent = *p;
f = rb_entry(parent, struct fq_flow, fq_node);
if (f->sk == sk) {
/* socket might have been reallocated, so check
* if its sk_hash is the same.
* It not, we need to refill credit with
* initial quantum
*/
if (unlikely(skb->sk &&
f->socket_hash != sk->sk_hash)) {
f->credit = q->initial_quantum;
f->socket_hash = sk->sk_hash;
f->time_next_packet = 0ULL;
}
return f;
}
if (f->sk > sk)
p = &parent->rb_right;
else
p = &parent->rb_left;
}
f = kmem_cache_zalloc(fq_flow_cachep, GFP_ATOMIC | __GFP_NOWARN);
if (unlikely(!f)) {
q->stat_allocation_errors++;
return &q->internal;
}
fq_flow_set_detached(f);
f->sk = sk;
if (skb->sk)
f->socket_hash = sk->sk_hash;
f->credit = q->initial_quantum;
rb_link_node(&f->fq_node, parent, p);
rb_insert_color(&f->fq_node, root);
q->flows++;
q->inactive_flows++;
return f;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 372 | 97.89% | 5 | 71.43% |
Maciej Żenczykowski | 7 | 1.84% | 1 | 14.29% |
Geliang Tang | 1 | 0.26% | 1 | 14.29% |
Total | 380 | 100.00% | 7 | 100.00% |
/* remove one skb from head of flow queue */
static struct sk_buff *fq_dequeue_head(struct Qdisc *sch, struct fq_flow *flow)
{
struct sk_buff *skb = flow->head;
if (skb) {
flow->head = skb->next;
skb->next = NULL;
flow->qlen--;
qdisc_qstats_backlog_dec(sch, skb);
sch->q.qlen--;
}
return skb;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 66 | 95.65% | 2 | 66.67% |
John Fastabend | 3 | 4.35% | 1 | 33.33% |
Total | 69 | 100.00% | 3 | 100.00% |
/* We might add in the future detection of retransmits
* For the time being, just return false
*/
static bool skb_is_retransmit(struct sk_buff *skb)
{
return false;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 14 | 100.00% | 1 | 100.00% |
Total | 14 | 100.00% | 1 | 100.00% |
/* add skb to flow queue
* flow queue is a linked list, kind of FIFO, except for TCP retransmits
* We special case tcp retransmits to be transmitted before other packets.
* We rely on fact that TCP retransmits are unlikely, so we do not waste
* a separate queue or a pointer.
* head-> [retrans pkt 1]
* [retrans pkt 2]
* [ normal pkt 1]
* [ normal pkt 2]
* [ normal pkt 3]
* tail-> [ normal pkt 4]
*/
static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb)
{
struct sk_buff *prev, *head = flow->head;
skb->next = NULL;
if (!head) {
flow->head = skb;
flow->tail = skb;
return;
}
if (likely(!skb_is_retransmit(skb))) {
flow->tail->next = skb;
flow->tail = skb;
return;
}
/* This skb is a tcp retransmit,
* find the last retrans packet in the queue
*/
prev = NULL;
while (skb_is_retransmit(head)) {
prev = head;
head = head->next;
if (!head)
break;
}
if (!prev) { /* no rtx packet in queue, become the new head */
skb->next = flow->head;
flow->head = skb;
} else {
if (prev == flow->tail)
flow->tail = skb;
else
skb->next = prev->next;
prev->next = skb;
}
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 166 | 100.00% | 1 | 100.00% |
Total | 166 | 100.00% | 1 | 100.00% |
static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
struct fq_sched_data *q = qdisc_priv(sch);
struct fq_flow *f;
if (unlikely(sch->q.qlen >= sch->limit))
return qdisc_drop(skb, sch, to_free);
f = fq_classify(skb, q);
if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
q->stat_flows_plimit++;
return qdisc_drop(skb, sch, to_free);
}
f->qlen++;
if (skb_is_retransmit(skb))
q->stat_tcp_retrans++;
qdisc_qstats_backlog_inc(sch, skb);
if (fq_flow_is_detached(f)) {
fq_flow_add_tail(&q->new_flows, f);
if (time_after(jiffies, f->age + q->flow_refill_delay))
f->credit = max_t(u32, f->credit, q->quantum);
q->inactive_flows--;
}
/* Note: this overwrites f->age */
flow_queue_add(f, skb);
if (unlikely(f == &q->internal)) {
q->stat_internal_packets++;
}
sch->q.qlen++;
return NET_XMIT_SUCCESS;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 222 | 98.67% | 3 | 75.00% |
John Fastabend | 3 | 1.33% | 1 | 25.00% |
Total | 225 | 100.00% | 4 | 100.00% |
static void fq_check_throttled(struct fq_sched_data *q, u64 now)
{
unsigned long sample;
struct rb_node *p;
if (q->time_next_delayed_flow > now)
return;
/* Update unthrottle latency EWMA.
* This is cheap and can help diagnosing timer/latency problems.
*/
sample = (unsigned long)(now - q->time_next_delayed_flow);
q->unthrottle_latency_ns -= q->unthrottle_latency_ns >> 3;
q->unthrottle_latency_ns += sample >> 3;
q->time_next_delayed_flow = ~0ULL;
while ((p = rb_first(&q->delayed)) != NULL) {
struct fq_flow *f = rb_entry(p, struct fq_flow, rate_node);
if (f->time_next_packet > now) {
q->time_next_delayed_flow = f->time_next_packet;
break;
}
rb_erase(p, &q->delayed);
q->throttled_flows--;
fq_flow_add_tail(&q->old_flows, f);
}
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 148 | 99.33% | 2 | 66.67% |
Geliang Tang | 1 | 0.67% | 1 | 33.33% |
Total | 149 | 100.00% | 3 | 100.00% |
static struct sk_buff *fq_dequeue(struct Qdisc *sch)
{
struct fq_sched_data *q = qdisc_priv(sch);
u64 now = ktime_get_ns();
struct fq_flow_head *head;
struct sk_buff *skb;
struct fq_flow *f;
u32 rate, plen;
skb = fq_dequeue_head(sch, &q->internal);
if (skb)
goto out;
fq_check_throttled(q, now);
begin:
head = &q->new_flows;
if (!head->first) {
head = &q->old_flows;
if (!head->first) {
if (q->time_next_delayed_flow != ~0ULL)
qdisc_watchdog_schedule_ns(&q->watchdog,
q->time_next_delayed_flow);
return NULL;
}
}
f = head->first;
if (f->credit <= 0) {
f->credit += q->quantum;
head->first = f->next;
fq_flow_add_tail(&q->old_flows, f);
goto begin;
}
skb = f->head;
if (unlikely(skb && now < f->time_next_packet &&
!skb_is_tcp_pure_ack(skb))) {
head->first = f->next;
fq_flow_set_throttled(q, f);
goto begin;
}
skb = fq_dequeue_head(sch, f);
if (!skb) {
head->first = f->next;
/* force a pass through old_flows to prevent starvation */
if ((head == &q->new_flows) && q->old_flows.first) {
fq_flow_add_tail(&q->old_flows, f);
} else {
fq_flow_set_detached(f);
q->inactive_flows++;
}
goto begin;
}
prefetch(&skb->end);
f->credit -= qdisc_pkt_len(skb);
if (!q->rate_enable)
goto out;
/* Do not pace locally generated ack packets */
if (skb_is_tcp_pure_ack(skb))
goto out;
rate = q->flow_max_rate;
if (skb->sk)
rate = min(skb->sk->sk_pacing_rate, rate);
if (rate <= q->low_rate_threshold) {
f->credit = 0;
plen = qdisc_pkt_len(skb);
} else {
plen = max(qdisc_pkt_len(skb), q->quantum);
if (f->credit > 0)
goto out;
}
if (rate != ~0U) {
u64 len = (u64)plen * NSEC_PER_SEC;
if (likely(rate))
do_div(len, rate);
/* Since socket rate can change later,
* clamp the delay to 1 second.
* Really, providers of too big packets should be fixed !
*/
if (unlikely(len > NSEC_PER_SEC)) {
len = NSEC_PER_SEC;
q->stat_pkts_too_long++;
}
/* Account for schedule/timers drifts.
* f->time_next_packet was set when prior packet was sent,
* and current time (@now) can be too late by tens of us.
*/
if (f->time_next_packet)
len -= min(len/2, now - f->time_next_packet);
f->time_next_packet = now + len;
}
out:
qdisc_bstats_update(sch, skb);
return skb;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 503 | 100.00% | 10 | 100.00% |
Total | 503 | 100.00% | 10 | 100.00% |
static void fq_flow_purge(struct fq_flow *flow)
{
rtnl_kfree_skbs(flow->head, flow->tail);
flow->head = NULL;
flow->qlen = 0;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 34 | 100.00% | 1 | 100.00% |
Total | 34 | 100.00% | 1 | 100.00% |
static void fq_reset(struct Qdisc *sch)
{
struct fq_sched_data *q = qdisc_priv(sch);
struct rb_root *root;
struct rb_node *p;
struct fq_flow *f;
unsigned int idx;
sch->q.qlen = 0;
sch->qstats.backlog = 0;
fq_flow_purge(&q->internal);
if (!q->fq_root)
return;
for (idx = 0; idx < (1U << q->fq_trees_log); idx++) {
root = &q->fq_root[idx];
while ((p = rb_first(root)) != NULL) {
f = rb_entry(p, struct fq_flow, fq_node);
rb_erase(p, root);
fq_flow_purge(f);
kmem_cache_free(fq_flow_cachep, f);
}
}
q->new_flows.first = NULL;
q->old_flows.first = NULL;
q->delayed = RB_ROOT;
q->flows = 0;
q->inactive_flows = 0;
q->throttled_flows = 0;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 188 | 99.47% | 3 | 75.00% |
Geliang Tang | 1 | 0.53% | 1 | 25.00% |
Total | 189 | 100.00% | 4 | 100.00% |
static void fq_rehash(struct fq_sched_data *q,
struct rb_root *old_array, u32 old_log,
struct rb_root *new_array, u32 new_log)
{
struct rb_node *op, **np, *parent;
struct rb_root *oroot, *nroot;
struct fq_flow *of, *nf;
int fcnt = 0;
u32 idx;
for (idx = 0; idx < (1U << old_log); idx++) {
oroot = &old_array[idx];
while ((op = rb_first(oroot)) != NULL) {
rb_erase(op, oroot);
of = rb_entry(op, struct fq_flow, fq_node);
if (fq_gc_candidate(of)) {
fcnt++;
kmem_cache_free(fq_flow_cachep, of);
continue;
}
nroot = &new_array[hash_ptr(of->sk, new_log)];
np = &nroot->rb_node;
parent = NULL;
while (*np) {
parent = *np;
nf = rb_entry(parent, struct fq_flow, fq_node);
BUG_ON(nf->sk == of->sk);
if (nf->sk > of->sk)
np = &parent->rb_right;
else
np = &parent->rb_left;
}
rb_link_node(&of->fq_node, parent, np);
rb_insert_color(&of->fq_node, nroot);
}
}
q->flows -= fcnt;
q->inactive_flows -= fcnt;
q->stat_gc_flows += fcnt;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 268 | 99.26% | 2 | 66.67% |
Geliang Tang | 2 | 0.74% | 1 | 33.33% |
Total | 270 | 100.00% | 3 | 100.00% |
static void *fq_alloc_node(size_t sz, int node)
{
void *ptr;
ptr = kmalloc_node(sz, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN, node);
if (!ptr)
ptr = vmalloc_node(sz, node);
return ptr;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 49 | 100.00% | 1 | 100.00% |
Total | 49 | 100.00% | 1 | 100.00% |
static void fq_free(void *addr)
{
kvfree(addr);
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 14 | 93.33% | 1 | 50.00% |
Américo Wang | 1 | 6.67% | 1 | 50.00% |
Total | 15 | 100.00% | 2 | 100.00% |
static int fq_resize(struct Qdisc *sch, u32 log)
{
struct fq_sched_data *q = qdisc_priv(sch);
struct rb_root *array;
void *old_fq_root;
u32 idx;
if (q->fq_root && log == q->fq_trees_log)
return 0;
/* If XPS was setup, we can allocate memory on right NUMA node */
array = fq_alloc_node(sizeof(struct rb_root) << log,
netdev_queue_numa_node_read(sch->dev_queue));
if (!array)
return -ENOMEM;
for (idx = 0; idx < (1U << log); idx++)
array[idx] = RB_ROOT;
sch_tree_lock(sch);
old_fq_root = q->fq_root;
if (old_fq_root)
fq_rehash(q, old_fq_root, q->fq_trees_log, array, log);
q->fq_root = array;
q->fq_trees_log = log;
sch_tree_unlock(sch);
fq_free(old_fq_root);
return 0;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Eric Dumazet | 160 | 100.00% | 3 | 100.00% |
Total | 160 | 100.00% | 3 | 100.00% |
static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
[TCA_FQ_PLIMIT] = { .type = NLA_U32 },
[TCA_FQ_FLOW_PLIMIT] = { .type = NLA_U32 },
[TCA_FQ_QUANTUM] = { .type = NLA_U32 },
[TCA_FQ_INITIAL_QUANTUM] = { .type = NLA_U32 },
[TCA_FQ_RATE_ENABLE] = { .type = NLA_U32 },
[TCA_FQ_FLOW_DEFAULT_RATE] = { .type = NLA_U32 },
[TCA_FQ_FLOW_MAX_RATE] = { .type = NLA_U32 },
[TCA_FQ_BUCKETS_LOG] = { .type = NLA_U32 },
[TCA_FQ_FLOW_REFILL_DELAY] = { .type = NLA_U32