From 8e4bff4cab0ddac6060645b0715210484d02ff40 Mon Sep 17 00:00:00 2001
From: Yuval Adam <_@yuv.al>
Date: Wed, 30 Aug 2017 08:25:59 +0000
Subject: Initial file dump from open source release

---
 net/core/gen_estimator.c | 321 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 321 insertions(+)
 create mode 100644 net/core/gen_estimator.c

(limited to 'net/core/gen_estimator.c')

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
new file mode 100644
index 00000000..d9d198aa
--- /dev/null
+++ b/net/core/gen_estimator.c
@@ -0,0 +1,321 @@
+/*
+ * net/sched/gen_estimator.c	Simple rate estimator.
+ *
+ *		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.
+ *
+ * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ * Changes:
+ *              Jamal Hadi Salim - moved it to net/core and reshulfed
+ *              names to make it usable in general net subsystem.
+ */
+
+#include <asm/uaccess.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/init.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <net/gen_stats.h>
+
+/*
+   This code is NOT intended to be used for statistics collection,
+   its purpose is to provide a base for statistical multiplexing
+   for controlled load service.
+   If you need only statistics, run a user level daemon which
+   periodically reads byte counters.
+
+   Unfortunately, rate estimation is not a very easy task.
+   F.e. I did not find a simple way to estimate the current peak rate
+   and even failed to formulate the problem 8)8)
+
+   So I preferred not to built an estimator into the scheduler,
+   but run this task separately.
+   Ideally, it should be kernel thread(s), but for now it runs
+   from timers, which puts apparent top bounds on the number of rated
+   flows, has minimal overhead on small, but is enough
+   to handle controlled load service, sets of aggregates.
+
+   We measure rate over A=(1<<interval) seconds and evaluate EWMA:
+
+   avrate = avrate*(1-W) + rate*W
+
+   where W is chosen as negative power of 2: W = 2^(-ewma_log)
+
+   The resulting time constant is:
+
+   T = A/(-ln(1-W))
+
+
+   NOTES.
+
+   * avbps is scaled by 2^5, avpps is scaled by 2^10.
+   * both values are reported as 32 bit unsigned values. bps can
+     overflow for fast links : max speed being 34360Mbit/sec
+   * Minimal interval is HZ/4=250msec (it is the greatest common divisor
+     for HZ=100 and HZ=1024 8)), maximal interval
+     is (HZ*2^EST_MAX_INTERVAL)/4 = 8sec. Shorter intervals
+     are too expensive, longer ones can be implemented
+     at user level painlessly.
+ */
+
+#define EST_MAX_INTERVAL	5
+
+struct gen_estimator
+{
+	struct list_head	list;
+	struct gnet_stats_basic_packed	*bstats;
+	struct gnet_stats_rate_est	*rate_est;
+	spinlock_t		*stats_lock;
+	int			ewma_log;
+	u64			last_bytes;
+	u64			avbps;
+	u32			last_packets;
+	u32			avpps;
+	struct rcu_head		e_rcu;
+	struct rb_node		node;
+};
+
+struct gen_estimator_head
+{
+	struct timer_list	timer;
+	struct list_head	list;
+};
+
+static struct gen_estimator_head elist[EST_MAX_INTERVAL+1];
+
+/* Protects against NULL dereference */
+static DEFINE_RWLOCK(est_lock);
+
+/* Protects against soft lockup during large deletion */
+static struct rb_root est_root = RB_ROOT;
+static DEFINE_SPINLOCK(est_tree_lock);
+
+static void est_timer(unsigned long arg)
+{
+	int idx = (int)arg;
+	struct gen_estimator *e;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(e, &elist[idx].list, list) {
+		u64 nbytes;
+		u64 brate;
+		u32 npackets;
+		u32 rate;
+
+		spin_lock(e->stats_lock);
+		read_lock(&est_lock);
+		if (e->bstats == NULL)
+			goto skip;
+
+		nbytes = e->bstats->bytes;
+		npackets = e->bstats->packets;
+		brate = (nbytes - e->last_bytes)<<(7 - idx);
+		e->last_bytes = nbytes;
+		e->avbps += (brate >> e->ewma_log) - (e->avbps >> e->ewma_log);
+		e->rate_est->bps = (e->avbps+0xF)>>5;
+
+		rate = (npackets - e->last_packets)<<(12 - idx);
+		e->last_packets = npackets;
+		e->avpps += (rate >> e->ewma_log) - (e->avpps >> e->ewma_log);
+		e->rate_est->pps = (e->avpps+0x1FF)>>10;
+skip:
+		read_unlock(&est_lock);
+		spin_unlock(e->stats_lock);
+	}
+
+	if (!list_empty(&elist[idx].list))
+		mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
+	rcu_read_unlock();
+}
+
+static void gen_add_node(struct gen_estimator *est)
+{
+	struct rb_node **p = &est_root.rb_node, *parent = NULL;
+
+	while (*p) {
+		struct gen_estimator *e;
+
+		parent = *p;
+		e = rb_entry(parent, struct gen_estimator, node);
+
+		if (est->bstats > e->bstats)
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+	rb_link_node(&est->node, parent, p);
+	rb_insert_color(&est->node, &est_root);
+}
+
+static
+struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats,
+				    const struct gnet_stats_rate_est *rate_est)
+{
+	struct rb_node *p = est_root.rb_node;
+
+	while (p) {
+		struct gen_estimator *e;
+
+		e = rb_entry(p, struct gen_estimator, node);
+
+		if (bstats > e->bstats)
+			p = p->rb_right;
+		else if (bstats < e->bstats || rate_est != e->rate_est)
+			p = p->rb_left;
+		else
+			return e;
+	}
+	return NULL;
+}
+
+/**
+ * gen_new_estimator - create a new rate estimator
+ * @bstats: basic statistics
+ * @rate_est: rate estimator statistics
+ * @stats_lock: statistics lock
+ * @opt: rate estimator configuration TLV
+ *
+ * Creates a new rate estimator with &bstats as source and &rate_est
+ * as destination. A new timer with the interval specified in the
+ * configuration TLV is created. Upon each interval, the latest statistics
+ * will be read from &bstats and the estimated rate will be stored in
+ * &rate_est with the statistics lock grabed during this period.
+ *
+ * Returns 0 on success or a negative error code.
+ *
+ */
+int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
+		      struct gnet_stats_rate_est *rate_est,
+		      spinlock_t *stats_lock,
+		      struct nlattr *opt)
+{
+	struct gen_estimator *est;
+	struct gnet_estimator *parm = nla_data(opt);
+	int idx;
+
+	if (nla_len(opt) < sizeof(*parm))
+		return -EINVAL;
+
+	if (parm->interval < -2 || parm->interval > 3)
+		return -EINVAL;
+
+	est = kzalloc(sizeof(*est), GFP_KERNEL);
+	if (est == NULL)
+		return -ENOBUFS;
+
+	idx = parm->interval + 2;
+	est->bstats = bstats;
+	est->rate_est = rate_est;
+	est->stats_lock = stats_lock;
+	est->ewma_log = parm->ewma_log;
+	est->last_bytes = bstats->bytes;
+	est->avbps = rate_est->bps<<5;
+	est->last_packets = bstats->packets;
+	est->avpps = rate_est->pps<<10;
+
+	spin_lock_bh(&est_tree_lock);
+	if (!elist[idx].timer.function) {
+		INIT_LIST_HEAD(&elist[idx].list);
+		setup_timer(&elist[idx].timer, est_timer, idx);
+	}
+
+	if (list_empty(&elist[idx].list))
+		mod_timer(&elist[idx].timer, jiffies + ((HZ/4) << idx));
+
+	list_add_rcu(&est->list, &elist[idx].list);
+	gen_add_node(est);
+	spin_unlock_bh(&est_tree_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(gen_new_estimator);
+
+/**
+ * gen_kill_estimator - remove a rate estimator
+ * @bstats: basic statistics
+ * @rate_est: rate estimator statistics
+ *
+ * Removes the rate estimator specified by &bstats and &rate_est.
+ *
+ * Note : Caller should respect an RCU grace period before freeing stats_lock
+ */
+void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
+			struct gnet_stats_rate_est *rate_est)
+{
+	struct gen_estimator *e;
+
+	spin_lock_bh(&est_tree_lock);
+	while ((e = gen_find_node(bstats, rate_est))) {
+		rb_erase(&e->node, &est_root);
+
+		write_lock(&est_lock);
+		e->bstats = NULL;
+		write_unlock(&est_lock);
+
+		list_del_rcu(&e->list);
+		kfree_rcu(e, e_rcu);
+	}
+	spin_unlock_bh(&est_tree_lock);
+}
+EXPORT_SYMBOL(gen_kill_estimator);
+
+/**
+ * gen_replace_estimator - replace rate estimator configuration
+ * @bstats: basic statistics
+ * @rate_est: rate estimator statistics
+ * @stats_lock: statistics lock
+ * @opt: rate estimator configuration TLV
+ *
+ * Replaces the configuration of a rate estimator by calling
+ * gen_kill_estimator() and gen_new_estimator().
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
+			  struct gnet_stats_rate_est *rate_est,
+			  spinlock_t *stats_lock, struct nlattr *opt)
+{
+	gen_kill_estimator(bstats, rate_est);
+	return gen_new_estimator(bstats, rate_est, stats_lock, opt);
+}
+EXPORT_SYMBOL(gen_replace_estimator);
+
+/**
+ * gen_estimator_active - test if estimator is currently in use
+ * @bstats: basic statistics
+ * @rate_est: rate estimator statistics
+ *
+ * Returns true if estimator is active, and false if not.
+ */
+bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
+			  const struct gnet_stats_rate_est *rate_est)
+{
+	bool res;
+
+	ASSERT_RTNL();
+
+	spin_lock_bh(&est_tree_lock);
+	res = gen_find_node(bstats, rate_est) != NULL;
+	spin_unlock_bh(&est_tree_lock);
+
+	return res;
+}
+EXPORT_SYMBOL(gen_estimator_active);
-- 
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