Commit 557fc4a0 authored by Michal Kazior's avatar Michal Kazior Committed by David S. Miller

fq: add fair queuing framework

This works on the same implementation principle as
codel*.h, i.e. there's a generic header with
structures and macros and a implementation header
carrying function definitions to include in given,
e.g. driver or module.

The fairness logic comes from
net/sched/sch_fq_codel.c but is generalized so it
is more flexible and easier to re-use.
Signed-off-by: default avatarMichal Kazior <michal.kazior@tieto.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 05d82c42
/*
* Copyright (c) 2016 Qualcomm Atheros, Inc
*
* GPL v2
*
* Based on net/sched/sch_fq_codel.c
*/
#ifndef __NET_SCHED_FQ_H
#define __NET_SCHED_FQ_H
struct fq_tin;
/**
* struct fq_flow - per traffic flow queue
*
* @tin: owner of this flow. Used to manage collisions, i.e. when a packet
* hashes to an index which points to a flow that is already owned by a
* different tin the packet is destined to. In such case the implementer
* must provide a fallback flow
* @flowchain: can be linked to fq_tin's new_flows or old_flows. Used for DRR++
* (deficit round robin) based round robin queuing similar to the one
* found in net/sched/sch_fq_codel.c
* @backlogchain: can be linked to other fq_flow and fq. Used to keep track of
* fat flows and efficient head-dropping if packet limit is reached
* @queue: sk_buff queue to hold packets
* @backlog: number of bytes pending in the queue. The number of packets can be
* found in @queue.qlen
* @deficit: used for DRR++
*/
struct fq_flow {
struct fq_tin *tin;
struct list_head flowchain;
struct list_head backlogchain;
struct sk_buff_head queue;
u32 backlog;
int deficit;
};
/**
* struct fq_tin - a logical container of fq_flows
*
* Used to group fq_flows into a logical aggregate. DRR++ scheme is used to
* pull interleaved packets out of the associated flows.
*
* @new_flows: linked list of fq_flow
* @old_flows: linked list of fq_flow
*/
struct fq_tin {
struct list_head new_flows;
struct list_head old_flows;
u32 backlog_bytes;
u32 backlog_packets;
u32 overlimit;
u32 collisions;
u32 flows;
u32 tx_bytes;
u32 tx_packets;
};
/**
* struct fq - main container for fair queuing purposes
*
* @backlogs: linked to fq_flows. Used to maintain fat flows for efficient
* head-dropping when @backlog reaches @limit
* @limit: max number of packets that can be queued across all flows
* @backlog: number of packets queued across all flows
*/
struct fq {
struct fq_flow *flows;
struct list_head backlogs;
spinlock_t lock;
u32 flows_cnt;
u32 perturbation;
u32 limit;
u32 quantum;
u32 backlog;
u32 overlimit;
u32 collisions;
};
typedef struct sk_buff *fq_tin_dequeue_t(struct fq *,
struct fq_tin *,
struct fq_flow *flow);
typedef void fq_skb_free_t(struct fq *,
struct fq_tin *,
struct fq_flow *,
struct sk_buff *);
typedef struct fq_flow *fq_flow_get_default_t(struct fq *,
struct fq_tin *,
int idx,
struct sk_buff *);
#endif
/*
* Copyright (c) 2016 Qualcomm Atheros, Inc
*
* GPL v2
*
* Based on net/sched/sch_fq_codel.c
*/
#ifndef __NET_SCHED_FQ_IMPL_H
#define __NET_SCHED_FQ_IMPL_H
#include <net/fq.h>
/* functions that are embedded into includer */
static struct sk_buff *fq_flow_dequeue(struct fq *fq,
struct fq_flow *flow)
{
struct fq_tin *tin = flow->tin;
struct fq_flow *i;
struct sk_buff *skb;
lockdep_assert_held(&fq->lock);
skb = __skb_dequeue(&flow->queue);
if (!skb)
return NULL;
tin->backlog_bytes -= skb->len;
tin->backlog_packets--;
flow->backlog -= skb->len;
fq->backlog--;
if (flow->backlog == 0) {
list_del_init(&flow->backlogchain);
} else {
i = flow;
list_for_each_entry_continue(i, &fq->backlogs, backlogchain)
if (i->backlog < flow->backlog)
break;
list_move_tail(&flow->backlogchain,
&i->backlogchain);
}
return skb;
}
static struct sk_buff *fq_tin_dequeue(struct fq *fq,
struct fq_tin *tin,
fq_tin_dequeue_t dequeue_func)
{
struct fq_flow *flow;
struct list_head *head;
struct sk_buff *skb;
lockdep_assert_held(&fq->lock);
begin:
head = &tin->new_flows;
if (list_empty(head)) {
head = &tin->old_flows;
if (list_empty(head))
return NULL;
}
flow = list_first_entry(head, struct fq_flow, flowchain);
if (flow->deficit <= 0) {
flow->deficit += fq->quantum;
list_move_tail(&flow->flowchain,
&tin->old_flows);
goto begin;
}
skb = dequeue_func(fq, tin, flow);
if (!skb) {
/* force a pass through old_flows to prevent starvation */
if ((head == &tin->new_flows) &&
!list_empty(&tin->old_flows)) {
list_move_tail(&flow->flowchain, &tin->old_flows);
} else {
list_del_init(&flow->flowchain);
flow->tin = NULL;
}
goto begin;
}
flow->deficit -= skb->len;
tin->tx_bytes += skb->len;
tin->tx_packets++;
return skb;
}
static struct fq_flow *fq_flow_classify(struct fq *fq,
struct fq_tin *tin,
struct sk_buff *skb,
fq_flow_get_default_t get_default_func)
{
struct fq_flow *flow;
u32 hash;
u32 idx;
lockdep_assert_held(&fq->lock);
hash = skb_get_hash_perturb(skb, fq->perturbation);
idx = reciprocal_scale(hash, fq->flows_cnt);
flow = &fq->flows[idx];
if (flow->tin && flow->tin != tin) {
flow = get_default_func(fq, tin, idx, skb);
tin->collisions++;
fq->collisions++;
}
if (!flow->tin)
tin->flows++;
return flow;
}
static void fq_tin_enqueue(struct fq *fq,
struct fq_tin *tin,
struct sk_buff *skb,
fq_skb_free_t free_func,
fq_flow_get_default_t get_default_func)
{
struct fq_flow *flow;
struct fq_flow *i;
lockdep_assert_held(&fq->lock);
flow = fq_flow_classify(fq, tin, skb, get_default_func);
flow->tin = tin;
flow->backlog += skb->len;
tin->backlog_bytes += skb->len;
tin->backlog_packets++;
fq->backlog++;
if (list_empty(&flow->backlogchain))
list_add_tail(&flow->backlogchain, &fq->backlogs);
i = flow;
list_for_each_entry_continue_reverse(i, &fq->backlogs,
backlogchain)
if (i->backlog > flow->backlog)
break;
list_move(&flow->backlogchain, &i->backlogchain);
if (list_empty(&flow->flowchain)) {
flow->deficit = fq->quantum;
list_add_tail(&flow->flowchain,
&tin->new_flows);
}
__skb_queue_tail(&flow->queue, skb);
if (fq->backlog > fq->limit) {
flow = list_first_entry_or_null(&fq->backlogs,
struct fq_flow,
backlogchain);
if (!flow)
return;
skb = fq_flow_dequeue(fq, flow);
if (!skb)
return;
free_func(fq, flow->tin, flow, skb);
flow->tin->overlimit++;
fq->overlimit++;
}
}
static void fq_flow_reset(struct fq *fq,
struct fq_flow *flow,
fq_skb_free_t free_func)
{
struct sk_buff *skb;
while ((skb = fq_flow_dequeue(fq, flow)))
free_func(fq, flow->tin, flow, skb);
if (!list_empty(&flow->flowchain))
list_del_init(&flow->flowchain);
if (!list_empty(&flow->backlogchain))
list_del_init(&flow->backlogchain);
flow->tin = NULL;
WARN_ON_ONCE(flow->backlog);
}
static void fq_tin_reset(struct fq *fq,
struct fq_tin *tin,
fq_skb_free_t free_func)
{
struct list_head *head;
struct fq_flow *flow;
for (;;) {
head = &tin->new_flows;
if (list_empty(head)) {
head = &tin->old_flows;
if (list_empty(head))
break;
}
flow = list_first_entry(head, struct fq_flow, flowchain);
fq_flow_reset(fq, flow, free_func);
}
WARN_ON_ONCE(tin->backlog_bytes);
WARN_ON_ONCE(tin->backlog_packets);
}
static void fq_flow_init(struct fq_flow *flow)
{
INIT_LIST_HEAD(&flow->flowchain);
INIT_LIST_HEAD(&flow->backlogchain);
__skb_queue_head_init(&flow->queue);
}
static void fq_tin_init(struct fq_tin *tin)
{
INIT_LIST_HEAD(&tin->new_flows);
INIT_LIST_HEAD(&tin->old_flows);
}
static int fq_init(struct fq *fq, int flows_cnt)
{
int i;
memset(fq, 0, sizeof(fq[0]));
INIT_LIST_HEAD(&fq->backlogs);
spin_lock_init(&fq->lock);
fq->flows_cnt = max_t(u32, flows_cnt, 1);
fq->perturbation = prandom_u32();
fq->quantum = 300;
fq->limit = 8192;
fq->flows = kcalloc(fq->flows_cnt, sizeof(fq->flows[0]), GFP_KERNEL);
if (!fq->flows)
return -ENOMEM;
for (i = 0; i < fq->flows_cnt; i++)
fq_flow_init(&fq->flows[i]);
return 0;
}
static void fq_reset(struct fq *fq,
fq_skb_free_t free_func)
{
int i;
for (i = 0; i < fq->flows_cnt; i++)
fq_flow_reset(fq, &fq->flows[i], free_func);
kfree(fq->flows);
fq->flows = NULL;
}
#endif
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