net-sched: add dynamically sized qdisc class hash helpers

Currently all qdiscs which allow to create classes uses a fixed sized hash
table with size 16 to hash the classes. This causes a large bottleneck
when using thousands of classes and unbound filters.

Add helpers for dynamically sized class hashes to fix this. The following
patches will convert the qdiscs to use them.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 104 insertions, 0 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 10f01ad04380..e9ebc7af049e 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -316,6 +316,110 @@ void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
 }
 EXPORT_SYMBOL(qdisc_watchdog_cancel);
 
+struct hlist_head *qdisc_class_hash_alloc(unsigned int n)
+{
+	unsigned int size = n * sizeof(struct hlist_head), i;
+	struct hlist_head *h;
+
+	if (size <= PAGE_SIZE)
+		h = kmalloc(size, GFP_KERNEL);
+	else
+		h = (struct hlist_head *)
+			__get_free_pages(GFP_KERNEL, get_order(size));
+
+	if (h != NULL) {
+		for (i = 0; i < n; i++)
+			INIT_HLIST_HEAD(&h[i]);
+	}
+	return h;
+}
+
+static void qdisc_class_hash_free(struct hlist_head *h, unsigned int n)
+{
+	unsigned int size = n * sizeof(struct hlist_head);
+
+	if (size <= PAGE_SIZE)
+		kfree(h);
+	else
+		free_pages((unsigned long)h, get_order(size));
+}
+
+void qdisc_class_hash_grow(struct Qdisc *sch, struct Qdisc_class_hash *clhash)
+{
+	struct Qdisc_class_common *cl;
+	struct hlist_node *n, *next;
+	struct hlist_head *nhash, *ohash;
+	unsigned int nsize, nmask, osize;
+	unsigned int i, h;
+
+	/* Rehash when load factor exceeds 0.75 */
+	if (clhash->hashelems * 4 <= clhash->hashsize * 3)
+		return;
+	nsize = clhash->hashsize * 2;
+	nmask = nsize - 1;
+	nhash = qdisc_class_hash_alloc(nsize);
+	if (nhash == NULL)
+		return;
+
+	ohash = clhash->hash;
+	osize = clhash->hashsize;
+
+	sch_tree_lock(sch);
+	for (i = 0; i < osize; i++) {
+		hlist_for_each_entry_safe(cl, n, next, &ohash[i], hnode) {
+			h = qdisc_class_hash(cl->classid, nmask);
+			hlist_add_head(&cl->hnode, &nhash[h]);
+		}
+	}
+	clhash->hash     = nhash;
+	clhash->hashsize = nsize;
+	clhash->hashmask = nmask;
+	sch_tree_unlock(sch);
+
+	qdisc_class_hash_free(ohash, osize);
+}
+EXPORT_SYMBOL(qdisc_class_hash_grow);
+
+int qdisc_class_hash_init(struct Qdisc_class_hash *clhash)
+{
+	unsigned int size = 4;
+
+	clhash->hash = qdisc_class_hash_alloc(size);
+	if (clhash->hash == NULL)
+		return -ENOMEM;
+	clhash->hashsize  = size;
+	clhash->hashmask  = size - 1;
+	clhash->hashelems = 0;
+	return 0;
+}
+EXPORT_SYMBOL(qdisc_class_hash_init);
+
+void qdisc_class_hash_destroy(struct Qdisc_class_hash *clhash)
+{
+	qdisc_class_hash_free(clhash->hash, clhash->hashsize);
+}
+EXPORT_SYMBOL(qdisc_class_hash_destroy);
+
+void qdisc_class_hash_insert(struct Qdisc_class_hash *clhash,
+			     struct Qdisc_class_common *cl)
+{
+	unsigned int h;
+
+	INIT_HLIST_NODE(&cl->hnode);
+	h = qdisc_class_hash(cl->classid, clhash->hashmask);
+	hlist_add_head(&cl->hnode, &clhash->hash[h]);
+	clhash->hashelems++;
+}
+EXPORT_SYMBOL(qdisc_class_hash_insert);
+
+void qdisc_class_hash_remove(struct Qdisc_class_hash *clhash,
+			     struct Qdisc_class_common *cl)
+{
+	hlist_del(&cl->hnode);
+	clhash->hashelems--;
+}
+EXPORT_SYMBOL(qdisc_class_hash_remove);
+
 /* Allocate an unique handle from space managed by kernel */
 
 static u32 qdisc_alloc_handle(struct net_device *dev)