From b145425f269a17ed344d737f746b844dfac60c82 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 17 Jul 2017 02:56:10 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/net/inetpeer.h | 11 +- net/ipv4/inetpeer.c | 428 +++++++++-------------------------------- 2 files changed, 92 insertions(+), 347 deletions(-) diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h index f2a215fc78e4..950ed182f62f 100644 --- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -33,18 +33,12 @@ struct inetpeer_addr { }; struct inet_peer { - /* group together avl_left,avl_right,v4daddr to speedup lookups */ - struct inet_peer __rcu *avl_left, *avl_right; + struct rb_node rb_node; struct inetpeer_addr daddr; - __u32 avl_height; u32 metrics[RTAX_MAX]; u32 rate_tokens; /* rate limiting for ICMP */ unsigned long rate_last; - union { - struct list_head gc_list; - struct rcu_head gc_rcu; - }; /* * Once inet_peer is queued for deletion (refcnt == 0), following field * is not available: rid @@ -55,7 +49,6 @@ struct inet_peer { atomic_t rid; /* Frag reception counter */ }; struct rcu_head rcu; - struct inet_peer *gc_next; }; /* following fields might be frequently dirtied */ @@ -64,7 +57,7 @@ struct inet_peer { }; struct inet_peer_base { - struct inet_peer __rcu *root; + struct rb_root rb_root; seqlock_t lock; int total; }; diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c index c5a117cc6619..337ad41bb80a 100644 --- a/net/ipv4/inetpeer.c +++ b/net/ipv4/inetpeer.c @@ -33,7 +33,7 @@ * also be removed if the pool is overloaded i.e. if the total amount of * entries is greater-or-equal than the threshold. * - * Node pool is organised as an AVL tree. + * Node pool is organised as an RB tree. * Such an implementation has been chosen not just for fun. It's a way to * prevent easy and efficient DoS attacks by creating hash collisions. A huge * amount of long living nodes in a single hash slot would significantly delay @@ -45,7 +45,7 @@ * AND reference count being 0. * 3. Global variable peer_total is modified under the pool lock. * 4. struct inet_peer fields modification: - * avl_left, avl_right, avl_parent, avl_height: pool lock + * rb_node: pool lock * refcnt: atomically against modifications on other CPU; * usually under some other lock to prevent node disappearing * daddr: unchangeable @@ -53,30 +53,15 @@ static struct kmem_cache *peer_cachep __read_mostly; -static LIST_HEAD(gc_list); -static const int gc_delay = 60 * HZ; -static struct delayed_work gc_work; -static DEFINE_SPINLOCK(gc_lock); - -#define node_height(x) x->avl_height - -#define peer_avl_empty ((struct inet_peer *)&peer_fake_node) -#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node) -static const struct inet_peer peer_fake_node = { - .avl_left = peer_avl_empty_rcu, - .avl_right = peer_avl_empty_rcu, - .avl_height = 0 -}; - void inet_peer_base_init(struct inet_peer_base *bp) { - bp->root = peer_avl_empty_rcu; + bp->rb_root = RB_ROOT; seqlock_init(&bp->lock); bp->total = 0; } EXPORT_SYMBOL_GPL(inet_peer_base_init); -#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */ +#define PEER_MAX_GC 32 /* Exported for sysctl_net_ipv4. */ int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more @@ -84,53 +69,6 @@ int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries m int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */ int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */ -static void inetpeer_gc_worker(struct work_struct *work) -{ - struct inet_peer *p, *n, *c; - struct list_head list; - - spin_lock_bh(&gc_lock); - list_replace_init(&gc_list, &list); - spin_unlock_bh(&gc_lock); - - if (list_empty(&list)) - return; - - list_for_each_entry_safe(p, n, &list, gc_list) { - - if (need_resched()) - cond_resched(); - - c = rcu_dereference_protected(p->avl_left, 1); - if (c != peer_avl_empty) { - list_add_tail(&c->gc_list, &list); - p->avl_left = peer_avl_empty_rcu; - } - - c = rcu_dereference_protected(p->avl_right, 1); - if (c != peer_avl_empty) { - list_add_tail(&c->gc_list, &list); - p->avl_right = peer_avl_empty_rcu; - } - - n = list_entry(p->gc_list.next, struct inet_peer, gc_list); - - if (refcount_read(&p->refcnt) == 1) { - list_del(&p->gc_list); - kmem_cache_free(peer_cachep, p); - } - } - - if (list_empty(&list)) - return; - - spin_lock_bh(&gc_lock); - list_splice(&list, &gc_list); - spin_unlock_bh(&gc_lock); - - schedule_delayed_work(&gc_work, gc_delay); -} - /* Called from ip_output.c:ip_init */ void __init inet_initpeers(void) { @@ -153,225 +91,62 @@ void __init inet_initpeers(void) sizeof(struct inet_peer), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); - - INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker); } -#define rcu_deref_locked(X, BASE) \ - rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock)) - -/* - * Called with local BH disabled and the pool lock held. - */ -#define lookup(_daddr, _stack, _base) \ -({ \ - struct inet_peer *u; \ - struct inet_peer __rcu **v; \ - \ - stackptr = _stack; \ - *stackptr++ = &_base->root; \ - for (u = rcu_deref_locked(_base->root, _base); \ - u != peer_avl_empty;) { \ - int cmp = inetpeer_addr_cmp(_daddr, &u->daddr); \ - if (cmp == 0) \ - break; \ - if (cmp == -1) \ - v = &u->avl_left; \ - else \ - v = &u->avl_right; \ - *stackptr++ = v; \ - u = rcu_deref_locked(*v, _base); \ - } \ - u; \ -}) - -/* - * Called with rcu_read_lock() - * Because we hold no lock against a writer, its quite possible we fall - * in an endless loop. - * But every pointer we follow is guaranteed to be valid thanks to RCU. - * We exit from this function if number of links exceeds PEER_MAXDEPTH - */ -static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr, - struct inet_peer_base *base) +/* Called with rcu_read_lock() or base->lock held */ +static struct inet_peer *lookup(const struct inetpeer_addr *daddr, + struct inet_peer_base *base, + unsigned int seq, + struct inet_peer *gc_stack[], + unsigned int *gc_cnt, + struct rb_node **parent_p, + struct rb_node ***pp_p) { - struct inet_peer *u = rcu_dereference(base->root); - int count = 0; + struct rb_node **pp, *parent; + struct inet_peer *p; - while (u != peer_avl_empty) { - int cmp = inetpeer_addr_cmp(daddr, &u->daddr); + pp = &base->rb_root.rb_node; + parent = NULL; + while (*pp) { + int cmp; + + parent = rcu_dereference_raw(*pp); + p = rb_entry(parent, struct inet_peer, rb_node); + cmp = inetpeer_addr_cmp(daddr, &p->daddr); if (cmp == 0) { - /* Before taking a reference, check if this entry was - * deleted (refcnt=0) - */ - if (!refcount_inc_not_zero(&u->refcnt)) { - u = NULL; - } - return u; + if (!refcount_inc_not_zero(&p->refcnt)) + break; + return p; + } + if (gc_stack) { + if (*gc_cnt < PEER_MAX_GC) + gc_stack[(*gc_cnt)++] = p; + } else if (unlikely(read_seqretry(&base->lock, seq))) { + break; } if (cmp == -1) - u = rcu_dereference(u->avl_left); + pp = &(*pp)->rb_left; else - u = rcu_dereference(u->avl_right); - if (unlikely(++count == PEER_MAXDEPTH)) - break; + pp = &(*pp)->rb_right; } + *parent_p = parent; + *pp_p = pp; return NULL; } -/* Called with local BH disabled and the pool lock held. */ -#define lookup_rightempty(start, base) \ -({ \ - struct inet_peer *u; \ - struct inet_peer __rcu **v; \ - *stackptr++ = &start->avl_left; \ - v = &start->avl_left; \ - for (u = rcu_deref_locked(*v, base); \ - u->avl_right != peer_avl_empty_rcu;) { \ - v = &u->avl_right; \ - *stackptr++ = v; \ - u = rcu_deref_locked(*v, base); \ - } \ - u; \ -}) - -/* Called with local BH disabled and the pool lock held. - * Variable names are the proof of operation correctness. - * Look into mm/map_avl.c for more detail description of the ideas. - */ -static void peer_avl_rebalance(struct inet_peer __rcu **stack[], - struct inet_peer __rcu ***stackend, - struct inet_peer_base *base) -{ - struct inet_peer __rcu **nodep; - struct inet_peer *node, *l, *r; - int lh, rh; - - while (stackend > stack) { - nodep = *--stackend; - node = rcu_deref_locked(*nodep, base); - l = rcu_deref_locked(node->avl_left, base); - r = rcu_deref_locked(node->avl_right, base); - lh = node_height(l); - rh = node_height(r); - if (lh > rh + 1) { /* l: RH+2 */ - struct inet_peer *ll, *lr, *lrl, *lrr; - int lrh; - ll = rcu_deref_locked(l->avl_left, base); - lr = rcu_deref_locked(l->avl_right, base); - lrh = node_height(lr); - if (lrh <= node_height(ll)) { /* ll: RH+1 */ - RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */ - RCU_INIT_POINTER(node->avl_right, r); /* r: RH */ - node->avl_height = lrh + 1; /* RH+1 or RH+2 */ - RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */ - RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */ - l->avl_height = node->avl_height + 1; - RCU_INIT_POINTER(*nodep, l); - } else { /* ll: RH, lr: RH+1 */ - lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */ - lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */ - RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */ - RCU_INIT_POINTER(node->avl_right, r); /* r: RH */ - node->avl_height = rh + 1; /* node: RH+1 */ - RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */ - RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */ - l->avl_height = rh + 1; /* l: RH+1 */ - RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */ - RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */ - lr->avl_height = rh + 2; - RCU_INIT_POINTER(*nodep, lr); - } - } else if (rh > lh + 1) { /* r: LH+2 */ - struct inet_peer *rr, *rl, *rlr, *rll; - int rlh; - rr = rcu_deref_locked(r->avl_right, base); - rl = rcu_deref_locked(r->avl_left, base); - rlh = node_height(rl); - if (rlh <= node_height(rr)) { /* rr: LH+1 */ - RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */ - RCU_INIT_POINTER(node->avl_left, l); /* l: LH */ - node->avl_height = rlh + 1; /* LH+1 or LH+2 */ - RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */ - RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */ - r->avl_height = node->avl_height + 1; - RCU_INIT_POINTER(*nodep, r); - } else { /* rr: RH, rl: RH+1 */ - rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */ - rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */ - RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */ - RCU_INIT_POINTER(node->avl_left, l); /* l: LH */ - node->avl_height = lh + 1; /* node: LH+1 */ - RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */ - RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */ - r->avl_height = lh + 1; /* r: LH+1 */ - RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */ - RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */ - rl->avl_height = lh + 2; - RCU_INIT_POINTER(*nodep, rl); - } - } else { - node->avl_height = (lh > rh ? lh : rh) + 1; - } - } -} - -/* Called with local BH disabled and the pool lock held. */ -#define link_to_pool(n, base) \ -do { \ - n->avl_height = 1; \ - n->avl_left = peer_avl_empty_rcu; \ - n->avl_right = peer_avl_empty_rcu; \ - /* lockless readers can catch us now */ \ - rcu_assign_pointer(**--stackptr, n); \ - peer_avl_rebalance(stack, stackptr, base); \ -} while (0) - static void inetpeer_free_rcu(struct rcu_head *head) { kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu)); } -static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base, - struct inet_peer __rcu **stack[PEER_MAXDEPTH]) -{ - struct inet_peer __rcu ***stackptr, ***delp; - - if (lookup(&p->daddr, stack, base) != p) - BUG(); - delp = stackptr - 1; /* *delp[0] == p */ - if (p->avl_left == peer_avl_empty_rcu) { - *delp[0] = p->avl_right; - --stackptr; - } else { - /* look for a node to insert instead of p */ - struct inet_peer *t; - t = lookup_rightempty(p, base); - BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t); - **--stackptr = t->avl_left; - /* t is removed, t->daddr > x->daddr for any - * x in p->avl_left subtree. - * Put t in the old place of p. */ - RCU_INIT_POINTER(*delp[0], t); - t->avl_left = p->avl_left; - t->avl_right = p->avl_right; - t->avl_height = p->avl_height; - BUG_ON(delp[1] != &p->avl_left); - delp[1] = &t->avl_left; /* was &p->avl_left */ - } - peer_avl_rebalance(stack, stackptr, base); - base->total--; - call_rcu(&p->rcu, inetpeer_free_rcu); -} - /* perform garbage collect on all items stacked during a lookup */ -static int inet_peer_gc(struct inet_peer_base *base, - struct inet_peer __rcu **stack[PEER_MAXDEPTH], - struct inet_peer __rcu ***stackptr) +static void inet_peer_gc(struct inet_peer_base *base, + struct inet_peer *gc_stack[], + unsigned int gc_cnt) { - struct inet_peer *p, *gchead = NULL; + struct inet_peer *p; __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);