inetpeer: remove AVL implementation in favor of RB tree
As discussed in Faro during Netfilter Workshop 2017, RB trees can be used with RCU, using a seqlock. Note that net/rxrpc/conn_service.c is already using this. This patch converts inetpeer from AVL tree to RB tree, since it allows to remove private AVL implementation in favor of shared RB code. $ size net/ipv4/inetpeer.before net/ipv4/inetpeer.after text data bss dec hex filename 3195 40 128 3363 d23 net/ipv4/inetpeer.before 1562 24 0 1586 632 net/ipv4/inetpeer.after The same technique can be used to speed up net/netfilter/nft_set_rbtree.c (removing rwlock contention in fast path) Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
David S. Miller
parent
27eac47b00
commit
b145425f26
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@ -33,18 +33,12 @@ struct inetpeer_addr {
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};
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struct inet_peer {
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/* group together avl_left,avl_right,v4daddr to speedup lookups */
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struct inet_peer __rcu *avl_left, *avl_right;
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struct rb_node rb_node;
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struct inetpeer_addr daddr;
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__u32 avl_height;
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u32 metrics[RTAX_MAX];
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u32 rate_tokens; /* rate limiting for ICMP */
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unsigned long rate_last;
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union {
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struct list_head gc_list;
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struct rcu_head gc_rcu;
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};
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/*
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* Once inet_peer is queued for deletion (refcnt == 0), following field
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* is not available: rid
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@ -55,7 +49,6 @@ struct inet_peer {
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atomic_t rid; /* Frag reception counter */
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};
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struct rcu_head rcu;
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struct inet_peer *gc_next;
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};
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/* following fields might be frequently dirtied */
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@ -64,7 +57,7 @@ struct inet_peer {
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};
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struct inet_peer_base {
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struct inet_peer __rcu *root;
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struct rb_root rb_root;
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seqlock_t lock;
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int total;
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};
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@ -33,7 +33,7 @@
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* also be removed if the pool is overloaded i.e. if the total amount of
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* entries is greater-or-equal than the threshold.
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*
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* Node pool is organised as an AVL tree.
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* Node pool is organised as an RB tree.
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* Such an implementation has been chosen not just for fun. It's a way to
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* prevent easy and efficient DoS attacks by creating hash collisions. A huge
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* amount of long living nodes in a single hash slot would significantly delay
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@ -45,7 +45,7 @@
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* AND reference count being 0.
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* 3. Global variable peer_total is modified under the pool lock.
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* 4. struct inet_peer fields modification:
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* avl_left, avl_right, avl_parent, avl_height: pool lock
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* rb_node: pool lock
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* refcnt: atomically against modifications on other CPU;
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* usually under some other lock to prevent node disappearing
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* daddr: unchangeable
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@ -53,30 +53,15 @@
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static struct kmem_cache *peer_cachep __read_mostly;
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static LIST_HEAD(gc_list);
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static const int gc_delay = 60 * HZ;
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static struct delayed_work gc_work;
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static DEFINE_SPINLOCK(gc_lock);
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#define node_height(x) x->avl_height
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#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
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#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
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static const struct inet_peer peer_fake_node = {
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.avl_left = peer_avl_empty_rcu,
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.avl_right = peer_avl_empty_rcu,
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.avl_height = 0
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};
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void inet_peer_base_init(struct inet_peer_base *bp)
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{
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bp->root = peer_avl_empty_rcu;
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bp->rb_root = RB_ROOT;
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seqlock_init(&bp->lock);
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bp->total = 0;
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}
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EXPORT_SYMBOL_GPL(inet_peer_base_init);
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#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
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#define PEER_MAX_GC 32
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/* Exported for sysctl_net_ipv4. */
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int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
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@ -84,53 +69,6 @@ int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries m
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int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
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int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
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static void inetpeer_gc_worker(struct work_struct *work)
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{
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struct inet_peer *p, *n, *c;
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struct list_head list;
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spin_lock_bh(&gc_lock);
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list_replace_init(&gc_list, &list);
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spin_unlock_bh(&gc_lock);
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if (list_empty(&list))
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return;
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list_for_each_entry_safe(p, n, &list, gc_list) {
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if (need_resched())
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cond_resched();
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c = rcu_dereference_protected(p->avl_left, 1);
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if (c != peer_avl_empty) {
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list_add_tail(&c->gc_list, &list);
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p->avl_left = peer_avl_empty_rcu;
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}
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c = rcu_dereference_protected(p->avl_right, 1);
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if (c != peer_avl_empty) {
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list_add_tail(&c->gc_list, &list);
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p->avl_right = peer_avl_empty_rcu;
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}
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n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
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if (refcount_read(&p->refcnt) == 1) {
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list_del(&p->gc_list);
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kmem_cache_free(peer_cachep, p);
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}
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}
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if (list_empty(&list))
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return;
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spin_lock_bh(&gc_lock);
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list_splice(&list, &gc_list);
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spin_unlock_bh(&gc_lock);
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schedule_delayed_work(&gc_work, gc_delay);
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}
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/* Called from ip_output.c:ip_init */
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void __init inet_initpeers(void)
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{
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@ -153,225 +91,62 @@ void __init inet_initpeers(void)
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sizeof(struct inet_peer),
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0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
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NULL);
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INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
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}
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#define rcu_deref_locked(X, BASE) \
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rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
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/*
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* Called with local BH disabled and the pool lock held.
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*/
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#define lookup(_daddr, _stack, _base) \
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({ \
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struct inet_peer *u; \
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struct inet_peer __rcu **v; \
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\
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stackptr = _stack; \
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*stackptr++ = &_base->root; \
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for (u = rcu_deref_locked(_base->root, _base); \
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u != peer_avl_empty;) { \
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int cmp = inetpeer_addr_cmp(_daddr, &u->daddr); \
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if (cmp == 0) \
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break; \
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if (cmp == -1) \
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v = &u->avl_left; \
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else \
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v = &u->avl_right; \
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*stackptr++ = v; \
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u = rcu_deref_locked(*v, _base); \
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} \
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u; \
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})
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/*
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* Called with rcu_read_lock()
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* Because we hold no lock against a writer, its quite possible we fall
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* in an endless loop.
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* But every pointer we follow is guaranteed to be valid thanks to RCU.
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* We exit from this function if number of links exceeds PEER_MAXDEPTH
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*/
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static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
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struct inet_peer_base *base)
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/* Called with rcu_read_lock() or base->lock held */
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static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
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struct inet_peer_base *base,
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unsigned int seq,
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struct inet_peer *gc_stack[],
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unsigned int *gc_cnt,
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struct rb_node **parent_p,
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struct rb_node ***pp_p)
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{
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struct inet_peer *u = rcu_dereference(base->root);
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int count = 0;
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struct rb_node **pp, *parent;
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struct inet_peer *p;
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while (u != peer_avl_empty) {
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int cmp = inetpeer_addr_cmp(daddr, &u->daddr);
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pp = &base->rb_root.rb_node;
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parent = NULL;
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while (*pp) {
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int cmp;
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parent = rcu_dereference_raw(*pp);
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p = rb_entry(parent, struct inet_peer, rb_node);
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cmp = inetpeer_addr_cmp(daddr, &p->daddr);
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if (cmp == 0) {
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/* Before taking a reference, check if this entry was
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* deleted (refcnt=0)
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*/
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if (!refcount_inc_not_zero(&u->refcnt)) {
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u = NULL;
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}
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return u;
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if (!refcount_inc_not_zero(&p->refcnt))
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break;
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return p;
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}
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if (gc_stack) {
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if (*gc_cnt < PEER_MAX_GC)
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gc_stack[(*gc_cnt)++] = p;
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} else if (unlikely(read_seqretry(&base->lock, seq))) {
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break;
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}
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if (cmp == -1)
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u = rcu_dereference(u->avl_left);
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pp = &(*pp)->rb_left;
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else
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u = rcu_dereference(u->avl_right);
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if (unlikely(++count == PEER_MAXDEPTH))
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break;
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pp = &(*pp)->rb_right;
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}
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*parent_p = parent;
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*pp_p = pp;
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return NULL;
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}
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/* Called with local BH disabled and the pool lock held. */
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#define lookup_rightempty(start, base) \
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({ \
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struct inet_peer *u; \
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struct inet_peer __rcu **v; \
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*stackptr++ = &start->avl_left; \
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v = &start->avl_left; \
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for (u = rcu_deref_locked(*v, base); \
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u->avl_right != peer_avl_empty_rcu;) { \
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v = &u->avl_right; \
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*stackptr++ = v; \
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u = rcu_deref_locked(*v, base); \
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} \
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u; \
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})
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/* Called with local BH disabled and the pool lock held.
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* Variable names are the proof of operation correctness.
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* Look into mm/map_avl.c for more detail description of the ideas.
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*/
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static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
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struct inet_peer __rcu ***stackend,
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struct inet_peer_base *base)
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{
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struct inet_peer __rcu **nodep;
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struct inet_peer *node, *l, *r;
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int lh, rh;
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while (stackend > stack) {
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nodep = *--stackend;
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node = rcu_deref_locked(*nodep, base);
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l = rcu_deref_locked(node->avl_left, base);
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r = rcu_deref_locked(node->avl_right, base);
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lh = node_height(l);
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rh = node_height(r);
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if (lh > rh + 1) { /* l: RH+2 */
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struct inet_peer *ll, *lr, *lrl, *lrr;
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int lrh;
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ll = rcu_deref_locked(l->avl_left, base);
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lr = rcu_deref_locked(l->avl_right, base);
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lrh = node_height(lr);
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if (lrh <= node_height(ll)) { /* ll: RH+1 */
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RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
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RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
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node->avl_height = lrh + 1; /* RH+1 or RH+2 */
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RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
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RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
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l->avl_height = node->avl_height + 1;
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RCU_INIT_POINTER(*nodep, l);
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} else { /* ll: RH, lr: RH+1 */
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lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
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lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
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RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
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RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
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node->avl_height = rh + 1; /* node: RH+1 */
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RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
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RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
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l->avl_height = rh + 1; /* l: RH+1 */
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RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
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RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
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lr->avl_height = rh + 2;
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RCU_INIT_POINTER(*nodep, lr);
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}
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} else if (rh > lh + 1) { /* r: LH+2 */
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struct inet_peer *rr, *rl, *rlr, *rll;
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int rlh;
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rr = rcu_deref_locked(r->avl_right, base);
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rl = rcu_deref_locked(r->avl_left, base);
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rlh = node_height(rl);
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if (rlh <= node_height(rr)) { /* rr: LH+1 */
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RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
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RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
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node->avl_height = rlh + 1; /* LH+1 or LH+2 */
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RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
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RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
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r->avl_height = node->avl_height + 1;
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RCU_INIT_POINTER(*nodep, r);
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} else { /* rr: RH, rl: RH+1 */
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rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
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rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
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RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
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RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
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node->avl_height = lh + 1; /* node: LH+1 */
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RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
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RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
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r->avl_height = lh + 1; /* r: LH+1 */
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RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
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RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
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rl->avl_height = lh + 2;
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RCU_INIT_POINTER(*nodep, rl);
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}
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} else {
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node->avl_height = (lh > rh ? lh : rh) + 1;
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}
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}
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}
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/* Called with local BH disabled and the pool lock held. */
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#define link_to_pool(n, base) \
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do { \
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n->avl_height = 1; \
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n->avl_left = peer_avl_empty_rcu; \
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n->avl_right = peer_avl_empty_rcu; \
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/* lockless readers can catch us now */ \
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rcu_assign_pointer(**--stackptr, n); \
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peer_avl_rebalance(stack, stackptr, base); \
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} while (0)
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static void inetpeer_free_rcu(struct rcu_head *head)
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{
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kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
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}
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static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
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struct inet_peer __rcu **stack[PEER_MAXDEPTH])
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{
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struct inet_peer __rcu ***stackptr, ***delp;
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if (lookup(&p->daddr, stack, base) != p)
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BUG();
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delp = stackptr - 1; /* *delp[0] == p */
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if (p->avl_left == peer_avl_empty_rcu) {
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*delp[0] = p->avl_right;
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--stackptr;
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} else {
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/* look for a node to insert instead of p */
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struct inet_peer *t;
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t = lookup_rightempty(p, base);
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BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
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**--stackptr = t->avl_left;
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/* t is removed, t->daddr > x->daddr for any
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* x in p->avl_left subtree.
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* Put t in the old place of p. */
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RCU_INIT_POINTER(*delp[0], t);
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t->avl_left = p->avl_left;
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t->avl_right = p->avl_right;
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t->avl_height = p->avl_height;
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BUG_ON(delp[1] != &p->avl_left);
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delp[1] = &t->avl_left; /* was &p->avl_left */
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}
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peer_avl_rebalance(stack, stackptr, base);
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base->total--;
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call_rcu(&p->rcu, inetpeer_free_rcu);
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}
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/* perform garbage collect on all items stacked during a lookup */
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static int inet_peer_gc(struct inet_peer_base *base,
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struct inet_peer __rcu **stack[PEER_MAXDEPTH],
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struct inet_peer __rcu ***stackptr)
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static void inet_peer_gc(struct inet_peer_base *base,
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struct inet_peer *gc_stack[],
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unsigned int gc_cnt)
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{
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struct inet_peer *p, *gchead = NULL;
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struct inet_peer *p;
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__u32 delta, ttl;
|
||||
int cnt = 0;
|
||||
int i;
|
||||
|
||||
if (base->total >= inet_peer_threshold)
|
||||
ttl = 0; /* be aggressive */
|
||||
|
|
@ -379,43 +154,38 @@ static int inet_peer_gc(struct inet_peer_base *base,
|
|||
ttl = inet_peer_maxttl
|
||||
- (inet_peer_maxttl - inet_peer_minttl) / HZ *
|
||||
base->total / inet_peer_threshold * HZ;
|
||||
stackptr--; /* last stack slot is peer_avl_empty */
|
||||
while (stackptr > stack) {
|
||||
stackptr--;
|
||||
p = rcu_deref_locked(**stackptr, base);
|
||||
if (refcount_read(&p->refcnt) == 1) {
|
||||
smp_rmb();
|
||||
delta = (__u32)jiffies - p->dtime;
|
||||
if (delta >= ttl && refcount_dec_if_one(&p->refcnt)) {
|
||||
p->gc_next = gchead;
|
||||
gchead = p;
|
||||
}
|
||||
for (i = 0; i < gc_cnt; i++) {
|
||||
p = gc_stack[i];
|
||||
delta = (__u32)jiffies - p->dtime;
|
||||
if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
|
||||
gc_stack[i] = NULL;
|
||||
}
|
||||
for (i = 0; i < gc_cnt; i++) {
|
||||
p = gc_stack[i];
|
||||
if (p) {
|
||||
rb_erase(&p->rb_node, &base->rb_root);
|
||||
base->total--;
|
||||
call_rcu(&p->rcu, inetpeer_free_rcu);
|
||||
}
|
||||
}
|
||||
while ((p = gchead) != NULL) {
|
||||
gchead = p->gc_next;
|
||||
cnt++;
|
||||
unlink_from_pool(p, base, stack);
|
||||
}
|
||||
return cnt;
|
||||
}
|
||||
|
||||
struct inet_peer *inet_getpeer(struct inet_peer_base *base,
|
||||
const struct inetpeer_addr *daddr,
|
||||
int create)
|
||||
{
|
||||
struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
|
||||
struct inet_peer *p;
|
||||
unsigned int sequence;
|
||||
int invalidated, gccnt = 0;
|
||||
struct inet_peer *p, *gc_stack[PEER_MAX_GC];
|
||||
struct rb_node **pp, *parent;
|
||||
unsigned int gc_cnt, seq;
|
||||
int invalidated;
|
||||
|
||||
/* Attempt a lockless lookup first.
|
||||
* Because of a concurrent writer, we might not find an existing entry.
|
||||
*/
|
||||
rcu_read_lock();
|
||||
sequence = read_seqbegin(&base->lock);
|
||||
p = lookup_rcu(daddr, base);
|
||||
invalidated = read_seqretry(&base->lock, sequence);
|
||||
seq = read_seqbegin(&base->lock);
|
||||
p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp);
|
||||
invalidated = read_seqretry(&base->lock, seq);
|
||||
rcu_read_unlock();
|
||||
|
||||
if (p)
|
||||
|
|
@ -428,36 +198,31 @@ struct inet_peer *inet_getpeer(struct inet_peer_base *base,
|
|||
/* retry an exact lookup, taking the lock before.
|
||||
* At least, nodes should be hot in our cache.
|
||||
*/
|
||||
parent = NULL;
|
||||
write_seqlock_bh(&base->lock);
|
||||
relookup:
|
||||
p = lookup(daddr, stack, base);
|
||||
if (p != peer_avl_empty) {
|
||||
refcount_inc(&p->refcnt);
|
||||
write_sequnlock_bh(&base->lock);
|
||||
return p;
|
||||
}
|
||||
if (!gccnt) {
|
||||
gccnt = inet_peer_gc(base, stack, stackptr);
|
||||
if (gccnt && create)
|
||||
goto relookup;
|
||||
}
|
||||
p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
|
||||
if (p) {
|
||||
p->daddr = *daddr;
|
||||
refcount_set(&p->refcnt, 2);
|
||||
atomic_set(&p->rid, 0);
|
||||
p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
|
||||
p->rate_tokens = 0;
|
||||
/* 60*HZ is arbitrary, but chosen enough high so that the first
|
||||
* calculation of tokens is at its maximum.
|
||||
*/
|
||||
p->rate_last = jiffies - 60*HZ;
|
||||
INIT_LIST_HEAD(&p->gc_list);
|
||||
|
||||
/* Link the node. */
|
||||
link_to_pool(p, base);
|
||||
base->total++;
|
||||
gc_cnt = 0;
|
||||
p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp);
|
||||
if (!p && create) {
|
||||
p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
|
||||
if (p) {
|
||||
p->daddr = *daddr;
|
||||
refcount_set(&p->refcnt, 2);
|
||||
atomic_set(&p->rid, 0);
|
||||
p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
|
||||
p->rate_tokens = 0;
|
||||
/* 60*HZ is arbitrary, but chosen enough high so that the first
|
||||
* calculation of tokens is at its maximum.
|
||||
*/
|
||||
p->rate_last = jiffies - 60*HZ;
|
||||
|
||||
rb_link_node(&p->rb_node, parent, pp);
|
||||
rb_insert_color(&p->rb_node, &base->rb_root);
|
||||
base->total++;
|
||||
}
|
||||
}
|
||||
if (gc_cnt)
|
||||
inet_peer_gc(base, gc_stack, gc_cnt);
|
||||
write_sequnlock_bh(&base->lock);
|
||||
|
||||
return p;
|
||||
|
|
@ -467,8 +232,9 @@ EXPORT_SYMBOL_GPL(inet_getpeer);
|
|||
void inet_putpeer(struct inet_peer *p)
|
||||
{
|
||||
p->dtime = (__u32)jiffies;
|
||||
smp_mb__before_atomic();
|
||||
refcount_dec(&p->refcnt);
|
||||
|
||||
if (refcount_dec_and_test(&p->refcnt))
|
||||
call_rcu(&p->rcu, inetpeer_free_rcu);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(inet_putpeer);
|
||||
|
||||
|
|
@ -513,30 +279,16 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
|
|||
}
|
||||
EXPORT_SYMBOL(inet_peer_xrlim_allow);
|
||||
|
||||
static void inetpeer_inval_rcu(struct rcu_head *head)
|
||||
{
|
||||
struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
|
||||
|
||||
spin_lock_bh(&gc_lock);
|
||||
list_add_tail(&p->gc_list, &gc_list);
|
||||
spin_unlock_bh(&gc_lock);
|
||||
|
||||
schedule_delayed_work(&gc_work, gc_delay);
|
||||
}
|
||||
|
||||
void inetpeer_invalidate_tree(struct inet_peer_base *base)
|
||||
{
|
||||
struct inet_peer *root;
|
||||
struct inet_peer *p, *n;
|
||||
|
||||
write_seqlock_bh(&base->lock);
|
||||
|
||||
root = rcu_deref_locked(base->root, base);
|
||||
if (root != peer_avl_empty) {
|
||||
base->root = peer_avl_empty_rcu;
|
||||
base->total = 0;
|
||||
call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
|
||||
rbtree_postorder_for_each_entry_safe(p, n, &base->rb_root, rb_node) {
|
||||
inet_putpeer(p);
|
||||
cond_resched();
|
||||
}
|
||||
|
||||
write_sequnlock_bh(&base->lock);
|
||||
base->rb_root = RB_ROOT;
|
||||
base->total = 0;
|
||||
}
|
||||
EXPORT_SYMBOL(inetpeer_invalidate_tree);
|
||||
|
|
|
|||
Loading…
Reference in New Issue