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>
diff --git a/include/net/fq.h b/include/net/fq.h
new file mode 100644
index 0000000..268b490
--- /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