From: Eric Dumazet <edumazet@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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 f2a215fc78e4686f597c4041796663a7a463e73f..950ed182f62f6f2e359b8ead28d903b4c6dc877f 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 c5a117cc66198ca0fe9d49e1c15f3c3110a0d634..337ad41bb80a5fcd3db7ac674292c5b5d462982e 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;
+
+ pp = &base->rb_root.rb_node;
+ parent = NULL;
+ while (*pp) {
+ int cmp;
- while (u != peer_avl_empty) {
- int cmp = inetpeer_addr_cmp(daddr, &u->daddr);
+ 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;
}
- while ((p = gchead) != NULL) {
- gchead = p->gc_next;
- cnt++;
- unlink_from_pool(p, base, stack);
+ 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);
+ }
}
- 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;
-
- write_seqlock_bh(&base->lock);
+ struct inet_peer *p, *n;
- 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);
--
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