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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: Michal Kazior <michal.kazior@tieto.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michal Kazior
David S. Miller
parent
05d82c4250
commit
557fc4a098
2 changed files with 364 additions and 0 deletions
95
include/net/fq.h
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95
include/net/fq.h
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@ -0,0 +1,95 @@
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/*
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* Copyright (c) 2016 Qualcomm Atheros, Inc
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*
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* GPL v2
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*
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* Based on net/sched/sch_fq_codel.c
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*/
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#ifndef __NET_SCHED_FQ_H
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#define __NET_SCHED_FQ_H
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struct fq_tin;
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/**
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* struct fq_flow - per traffic flow queue
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*
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* @tin: owner of this flow. Used to manage collisions, i.e. when a packet
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* hashes to an index which points to a flow that is already owned by a
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* different tin the packet is destined to. In such case the implementer
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* must provide a fallback flow
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* @flowchain: can be linked to fq_tin's new_flows or old_flows. Used for DRR++
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* (deficit round robin) based round robin queuing similar to the one
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* found in net/sched/sch_fq_codel.c
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* @backlogchain: can be linked to other fq_flow and fq. Used to keep track of
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* fat flows and efficient head-dropping if packet limit is reached
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* @queue: sk_buff queue to hold packets
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* @backlog: number of bytes pending in the queue. The number of packets can be
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* found in @queue.qlen
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* @deficit: used for DRR++
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*/
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struct fq_flow {
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struct fq_tin *tin;
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struct list_head flowchain;
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struct list_head backlogchain;
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struct sk_buff_head queue;
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u32 backlog;
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int deficit;
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};
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/**
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* struct fq_tin - a logical container of fq_flows
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*
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* Used to group fq_flows into a logical aggregate. DRR++ scheme is used to
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* pull interleaved packets out of the associated flows.
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*
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* @new_flows: linked list of fq_flow
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* @old_flows: linked list of fq_flow
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*/
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struct fq_tin {
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struct list_head new_flows;
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struct list_head old_flows;
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u32 backlog_bytes;
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u32 backlog_packets;
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u32 overlimit;
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u32 collisions;
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u32 flows;
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u32 tx_bytes;
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u32 tx_packets;
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};
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/**
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* struct fq - main container for fair queuing purposes
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*
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* @backlogs: linked to fq_flows. Used to maintain fat flows for efficient
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* head-dropping when @backlog reaches @limit
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* @limit: max number of packets that can be queued across all flows
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* @backlog: number of packets queued across all flows
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*/
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struct fq {
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struct fq_flow *flows;
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struct list_head backlogs;
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spinlock_t lock;
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u32 flows_cnt;
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u32 perturbation;
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u32 limit;
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u32 quantum;
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u32 backlog;
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u32 overlimit;
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u32 collisions;
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};
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typedef struct sk_buff *fq_tin_dequeue_t(struct fq *,
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struct fq_tin *,
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struct fq_flow *flow);
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typedef void fq_skb_free_t(struct fq *,
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struct fq_tin *,
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struct fq_flow *,
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struct sk_buff *);
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typedef struct fq_flow *fq_flow_get_default_t(struct fq *,
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struct fq_tin *,
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int idx,
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struct sk_buff *);
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#endif
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269
include/net/fq_impl.h
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269
include/net/fq_impl.h
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/*
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* Copyright (c) 2016 Qualcomm Atheros, Inc
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*
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* GPL v2
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*
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* Based on net/sched/sch_fq_codel.c
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*/
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#ifndef __NET_SCHED_FQ_IMPL_H
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#define __NET_SCHED_FQ_IMPL_H
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#include <net/fq.h>
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/* functions that are embedded into includer */
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static struct sk_buff *fq_flow_dequeue(struct fq *fq,
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struct fq_flow *flow)
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{
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struct fq_tin *tin = flow->tin;
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struct fq_flow *i;
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struct sk_buff *skb;
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lockdep_assert_held(&fq->lock);
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skb = __skb_dequeue(&flow->queue);
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if (!skb)
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return NULL;
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tin->backlog_bytes -= skb->len;
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tin->backlog_packets--;
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flow->backlog -= skb->len;
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fq->backlog--;
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if (flow->backlog == 0) {
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list_del_init(&flow->backlogchain);
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} else {
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i = flow;
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list_for_each_entry_continue(i, &fq->backlogs, backlogchain)
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if (i->backlog < flow->backlog)
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break;
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list_move_tail(&flow->backlogchain,
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&i->backlogchain);
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}
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return skb;
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}
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static struct sk_buff *fq_tin_dequeue(struct fq *fq,
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struct fq_tin *tin,
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fq_tin_dequeue_t dequeue_func)
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{
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struct fq_flow *flow;
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struct list_head *head;
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struct sk_buff *skb;
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lockdep_assert_held(&fq->lock);
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begin:
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head = &tin->new_flows;
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if (list_empty(head)) {
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head = &tin->old_flows;
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if (list_empty(head))
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return NULL;
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}
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flow = list_first_entry(head, struct fq_flow, flowchain);
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if (flow->deficit <= 0) {
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flow->deficit += fq->quantum;
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list_move_tail(&flow->flowchain,
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&tin->old_flows);
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goto begin;
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}
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skb = dequeue_func(fq, tin, flow);
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if (!skb) {
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/* force a pass through old_flows to prevent starvation */
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if ((head == &tin->new_flows) &&
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!list_empty(&tin->old_flows)) {
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list_move_tail(&flow->flowchain, &tin->old_flows);
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} else {
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list_del_init(&flow->flowchain);
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flow->tin = NULL;
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}
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goto begin;
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}
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flow->deficit -= skb->len;
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tin->tx_bytes += skb->len;
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tin->tx_packets++;
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return skb;
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}
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static struct fq_flow *fq_flow_classify(struct fq *fq,
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struct fq_tin *tin,
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struct sk_buff *skb,
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fq_flow_get_default_t get_default_func)
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{
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struct fq_flow *flow;
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u32 hash;
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u32 idx;
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lockdep_assert_held(&fq->lock);
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hash = skb_get_hash_perturb(skb, fq->perturbation);
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idx = reciprocal_scale(hash, fq->flows_cnt);
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flow = &fq->flows[idx];
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if (flow->tin && flow->tin != tin) {
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flow = get_default_func(fq, tin, idx, skb);
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tin->collisions++;
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fq->collisions++;
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}
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if (!flow->tin)
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tin->flows++;
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return flow;
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}
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static void fq_tin_enqueue(struct fq *fq,
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struct fq_tin *tin,
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struct sk_buff *skb,
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fq_skb_free_t free_func,
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fq_flow_get_default_t get_default_func)
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{
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struct fq_flow *flow;
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struct fq_flow *i;
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lockdep_assert_held(&fq->lock);
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flow = fq_flow_classify(fq, tin, skb, get_default_func);
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flow->tin = tin;
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flow->backlog += skb->len;
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tin->backlog_bytes += skb->len;
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tin->backlog_packets++;
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fq->backlog++;
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if (list_empty(&flow->backlogchain))
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list_add_tail(&flow->backlogchain, &fq->backlogs);
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i = flow;
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list_for_each_entry_continue_reverse(i, &fq->backlogs,
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backlogchain)
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if (i->backlog > flow->backlog)
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break;
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list_move(&flow->backlogchain, &i->backlogchain);
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if (list_empty(&flow->flowchain)) {
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flow->deficit = fq->quantum;
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list_add_tail(&flow->flowchain,
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&tin->new_flows);
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}
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__skb_queue_tail(&flow->queue, skb);
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if (fq->backlog > fq->limit) {
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flow = list_first_entry_or_null(&fq->backlogs,
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struct fq_flow,
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backlogchain);
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if (!flow)
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return;
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skb = fq_flow_dequeue(fq, flow);
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if (!skb)
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return;
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free_func(fq, flow->tin, flow, skb);
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flow->tin->overlimit++;
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fq->overlimit++;
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}
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}
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static void fq_flow_reset(struct fq *fq,
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struct fq_flow *flow,
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fq_skb_free_t free_func)
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{
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struct sk_buff *skb;
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while ((skb = fq_flow_dequeue(fq, flow)))
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free_func(fq, flow->tin, flow, skb);
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if (!list_empty(&flow->flowchain))
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list_del_init(&flow->flowchain);
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if (!list_empty(&flow->backlogchain))
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list_del_init(&flow->backlogchain);
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flow->tin = NULL;
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WARN_ON_ONCE(flow->backlog);
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}
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static void fq_tin_reset(struct fq *fq,
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struct fq_tin *tin,
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fq_skb_free_t free_func)
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{
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struct list_head *head;
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struct fq_flow *flow;
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for (;;) {
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head = &tin->new_flows;
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if (list_empty(head)) {
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head = &tin->old_flows;
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if (list_empty(head))
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break;
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}
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flow = list_first_entry(head, struct fq_flow, flowchain);
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fq_flow_reset(fq, flow, free_func);
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}
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WARN_ON_ONCE(tin->backlog_bytes);
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WARN_ON_ONCE(tin->backlog_packets);
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}
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static void fq_flow_init(struct fq_flow *flow)
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{
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INIT_LIST_HEAD(&flow->flowchain);
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INIT_LIST_HEAD(&flow->backlogchain);
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__skb_queue_head_init(&flow->queue);
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}
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static void fq_tin_init(struct fq_tin *tin)
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{
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INIT_LIST_HEAD(&tin->new_flows);
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INIT_LIST_HEAD(&tin->old_flows);
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}
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static int fq_init(struct fq *fq, int flows_cnt)
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{
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int i;
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memset(fq, 0, sizeof(fq[0]));
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INIT_LIST_HEAD(&fq->backlogs);
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spin_lock_init(&fq->lock);
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fq->flows_cnt = max_t(u32, flows_cnt, 1);
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fq->perturbation = prandom_u32();
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fq->quantum = 300;
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fq->limit = 8192;
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fq->flows = kcalloc(fq->flows_cnt, sizeof(fq->flows[0]), GFP_KERNEL);
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if (!fq->flows)
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return -ENOMEM;
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for (i = 0; i < fq->flows_cnt; i++)
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fq_flow_init(&fq->flows[i]);
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return 0;
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}
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static void fq_reset(struct fq *fq,
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fq_skb_free_t free_func)
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{
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int i;
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for (i = 0; i < fq->flows_cnt; i++)
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fq_flow_reset(fq, &fq->flows[i], free_func);
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kfree(fq->flows);
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fq->flows = NULL;
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}
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#endif
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