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authorMichal Kazior <michal.kazior@tieto.com>2016-04-22 14:20:13 +0200
committerDavid S. Miller <davem@davemloft.net>2016-04-25 16:45:53 -0400
commit557fc4a098039cf296fe33f118bab99a925fd881 (patch)
tree707eb27e1a7af4b9f5a84a85bf811bd32123289b /include
parent05d82c42509c2936e328a6b8b1e1cd5684f427ac (diff)
downloadlinux-557fc4a098039cf296fe33f118bab99a925fd881.tar.bz2
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>
Diffstat (limited to 'include')
-rw-r--r--include/net/fq.h95
-rw-r--r--include/net/fq_impl.h269
2 files changed, 364 insertions, 0 deletions
diff --git a/include/net/fq.h b/include/net/fq.h
new file mode 100644
index 000000000000..268b49049c37
--- /dev/null
+++ b/include/net/fq.h
@@ -0,0 +1,95 @@
+/*
+ * 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
diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h
new file mode 100644
index 000000000000..02eab7c51adb
--- /dev/null
+++ b/include/net/fq_impl.h
@@ -0,0 +1,269 @@
+/*
+ * 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