inetpeer: remove unused list
Andi Kleen and Tim Chen reported huge contention on inetpeer unused_peers.lock, on memcached workload on a 40 core machine, with disabled route cache. It appears we constantly flip peers refcnt between 0 and 1 values, and we must insert/remove peers from unused_peers.list, holding a contended spinlock. Remove this list completely and perform a garbage collection on-the-fly, at lookup time, using the expired nodes we met during the tree traversal. This removes a lot of code, makes locking more standard, and obsoletes two sysctls (inet_peer_gc_mintime and inet_peer_gc_maxtime). This also removes two pointers in inet_peer structure. There is still a false sharing effect because refcnt is in first cache line of object [were the links and keys used by lookups are located], we might move it at the end of inet_peer structure to let this first cache line mostly read by cpus. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Andi Kleen <andi@firstfloor.org> CC: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
David S. Miller
parent
9ad7c049f0
commit
4b9d9be839
@ -106,16 +106,6 @@ inet_peer_maxttl - INTEGER
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when the number of entries in the pool is very small).
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Measured in seconds.
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inet_peer_gc_mintime - INTEGER
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Minimum interval between garbage collection passes. This interval is
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in effect under high memory pressure on the pool.
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Measured in seconds.
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inet_peer_gc_maxtime - INTEGER
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Minimum interval between garbage collection passes. This interval is
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in effect under low (or absent) memory pressure on the pool.
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Measured in seconds.
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TCP variables:
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somaxconn - INTEGER
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@ -32,7 +32,6 @@ struct inet_peer {
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struct inet_peer __rcu *avl_left, *avl_right;
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struct inetpeer_addr daddr;
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__u32 avl_height;
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struct list_head unused;
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__u32 dtime; /* the time of last use of not
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* referenced entries */
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atomic_t refcnt;
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@ -56,6 +55,7 @@ struct inet_peer {
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struct inetpeer_addr_base redirect_learned;
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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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};
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@ -228,8 +228,6 @@ extern struct ctl_path net_ipv4_ctl_path[];
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extern int inet_peer_threshold;
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extern int inet_peer_minttl;
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extern int inet_peer_maxttl;
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extern int inet_peer_gc_mintime;
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extern int inet_peer_gc_maxtime;
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/* From ip_output.c */
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extern int sysctl_ip_dynaddr;
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@ -54,15 +54,11 @@
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* 1. Nodes may appear in the tree only with the pool lock held.
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* 2. Nodes may disappear from the tree only with the pool lock held
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* AND reference count being 0.
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* 3. Nodes appears and disappears from unused node list only under
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* "inet_peer_unused_lock".
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* 4. Global variable peer_total is modified under the pool lock.
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* 5. struct inet_peer fields modification:
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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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* unused: unused node list 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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* dtime: unused node list lock
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* daddr: unchangeable
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* ip_id_count: atomic value (no lock needed)
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*/
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@ -104,19 +100,6 @@ int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries m
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* aggressively at this stage */
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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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int inet_peer_gc_mintime __read_mostly = 10 * HZ;
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int inet_peer_gc_maxtime __read_mostly = 120 * HZ;
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static struct {
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struct list_head list;
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spinlock_t lock;
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} unused_peers = {
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.list = LIST_HEAD_INIT(unused_peers.list),
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.lock = __SPIN_LOCK_UNLOCKED(unused_peers.lock),
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};
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static void peer_check_expire(unsigned long dummy);
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static DEFINE_TIMER(peer_periodic_timer, peer_check_expire, 0, 0);
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/* Called from ip_output.c:ip_init */
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@ -142,21 +125,6 @@ void __init inet_initpeers(void)
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0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
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NULL);
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/* All the timers, started at system startup tend
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to synchronize. Perturb it a bit.
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*/
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peer_periodic_timer.expires = jiffies
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+ net_random() % inet_peer_gc_maxtime
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+ inet_peer_gc_maxtime;
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add_timer(&peer_periodic_timer);
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}
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/* Called with or without local BH being disabled. */
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static void unlink_from_unused(struct inet_peer *p)
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{
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spin_lock_bh(&unused_peers.lock);
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list_del_init(&p->unused);
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spin_unlock_bh(&unused_peers.lock);
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}
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static int addr_compare(const struct inetpeer_addr *a,
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@ -203,20 +171,6 @@ static int addr_compare(const struct inetpeer_addr *a,
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u; \
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})
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static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv)
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{
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int cur, old = atomic_read(ptr);
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while (old != u) {
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*newv = old + a;
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cur = atomic_cmpxchg(ptr, old, *newv);
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if (cur == old)
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return true;
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old = cur;
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}
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return false;
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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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@ -225,8 +179,7 @@ static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv)
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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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int *newrefcnt)
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struct inet_peer_base *base)
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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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@ -235,11 +188,9 @@ static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
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int cmp = addr_compare(daddr, &u->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, unlink_from_pool() sets refcnt=-1 to make
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* distinction between an unused entry (refcnt=0) and
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* a freed one.
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* deleted (refcnt=-1)
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*/
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if (!atomic_add_unless_return(&u->refcnt, 1, -1, newrefcnt))
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if (!atomic_add_unless(&u->refcnt, 1, -1))
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u = NULL;
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return u;
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}
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@ -366,137 +317,96 @@ static void inetpeer_free_rcu(struct rcu_head *head)
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kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
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}
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/* May be called with local BH enabled. */
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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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int do_free;
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struct inet_peer __rcu ***stackptr, ***delp;
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do_free = 0;
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write_seqlock_bh(&base->lock);
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/* Check the reference counter. It was artificially incremented by 1
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* in cleanup() function to prevent sudden disappearing. If we can
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* atomically (because of lockless readers) take this last reference,
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* it's safe to remove the node and free it later.
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* We use refcnt=-1 to alert lockless readers this entry is deleted.
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*/
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if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
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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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do_free = 1;
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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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write_sequnlock_bh(&base->lock);
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if (do_free)
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call_rcu(&p->rcu, inetpeer_free_rcu);
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else
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/* The node is used again. Decrease the reference counter
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* back. The loop "cleanup -> unlink_from_unused
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* -> unlink_from_pool -> putpeer -> link_to_unused
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* -> cleanup (for the same node)"
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* doesn't really exist because the entry will have a
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* recent deletion time and will not be cleaned again soon.
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*/
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inet_putpeer(p);
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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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static struct inet_peer_base *family_to_base(int family)
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{
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return (family == AF_INET ? &v4_peers : &v6_peers);
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return family == AF_INET ? &v4_peers : &v6_peers;
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}
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static struct inet_peer_base *peer_to_base(struct inet_peer *p)
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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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{
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return family_to_base(p->daddr.family);
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}
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struct inet_peer *p, *gchead = NULL;
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__u32 delta, ttl;
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int cnt = 0;
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/* May be called with local BH enabled. */
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static int cleanup_once(unsigned long ttl, struct inet_peer __rcu **stack[PEER_MAXDEPTH])
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{
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struct inet_peer *p = NULL;
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/* Remove the first entry from the list of unused nodes. */
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spin_lock_bh(&unused_peers.lock);
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if (!list_empty(&unused_peers.list)) {
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__u32 delta;
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p = list_first_entry(&unused_peers.list, struct inet_peer, unused);
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if (base->total >= inet_peer_threshold)
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ttl = 0; /* be aggressive */
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else
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ttl = inet_peer_maxttl
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- (inet_peer_maxttl - inet_peer_minttl) / HZ *
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base->total / inet_peer_threshold * HZ;
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stackptr--; /* last stack slot is peer_avl_empty */
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while (stackptr > stack) {
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stackptr--;
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p = rcu_deref_locked(**stackptr, base);
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delta = (__u32)jiffies - p->dtime;
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if (delta < ttl) {
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/* Do not prune fresh entries. */
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spin_unlock_bh(&unused_peers.lock);
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return -1;
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if (atomic_read(&p->refcnt) == 0 && delta >= ttl &&
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atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
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p->gc_next = gchead;
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gchead = p;
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}
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list_del_init(&p->unused);
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/* Grab an extra reference to prevent node disappearing
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* before unlink_from_pool() call. */
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atomic_inc(&p->refcnt);
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}
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spin_unlock_bh(&unused_peers.lock);
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if (p == NULL)
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/* It means that the total number of USED entries has
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* grown over inet_peer_threshold. It shouldn't really
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* happen because of entry limits in route cache. */
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return -1;
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unlink_from_pool(p, peer_to_base(p), stack);
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return 0;
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while ((p = gchead) != NULL) {
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gchead = p->gc_next;
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cnt++;
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unlink_from_pool(p, base, stack);
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}
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return cnt;
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}
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/* Called with or without local BH being disabled. */
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struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
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{
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struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
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struct inet_peer_base *base = family_to_base(daddr->family);
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struct inet_peer *p;
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unsigned int sequence;
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int invalidated, newrefcnt = 0;
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int invalidated, gccnt = 0;
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/* Look up for the address quickly, lockless.
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/* Attempt a lockless lookup first.
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* Because of a concurrent writer, we might not find an existing entry.
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*/
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rcu_read_lock();
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sequence = read_seqbegin(&base->lock);
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p = lookup_rcu(daddr, base, &newrefcnt);
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p = lookup_rcu(daddr, base);
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invalidated = read_seqretry(&base->lock, sequence);
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rcu_read_unlock();
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if (p) {
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found: /* The existing node has been found.
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* Remove the entry from unused list if it was there.
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*/
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if (newrefcnt == 1)
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unlink_from_unused(p);
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if (p)
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return p;
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}
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/* If no writer did a change during our lookup, we can return early. */
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if (!create && !invalidated)
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@ -506,11 +416,17 @@ found: /* The existing node has been found.
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* At least, nodes should be hot in our cache.
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*/
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write_seqlock_bh(&base->lock);
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relookup:
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p = lookup(daddr, stack, base);
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if (p != peer_avl_empty) {
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newrefcnt = atomic_inc_return(&p->refcnt);
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atomic_inc(&p->refcnt);
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write_sequnlock_bh(&base->lock);
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goto found;
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return p;
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}
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if (!gccnt) {
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gccnt = inet_peer_gc(base, stack, stackptr);
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if (gccnt && create)
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goto relookup;
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}
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p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
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if (p) {
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@ -525,7 +441,6 @@ found: /* The existing node has been found.
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p->pmtu_expires = 0;
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p->pmtu_orig = 0;
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memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
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INIT_LIST_HEAD(&p->unused);
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/* Link the node. */
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@ -534,63 +449,14 @@ found: /* The existing node has been found.
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}
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write_sequnlock_bh(&base->lock);
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if (base->total >= inet_peer_threshold)
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/* Remove one less-recently-used entry. */
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cleanup_once(0, stack);
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return p;
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}
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static int compute_total(void)
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{
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return v4_peers.total + v6_peers.total;
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}
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EXPORT_SYMBOL_GPL(inet_getpeer);
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/* Called with local BH disabled. */
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static void peer_check_expire(unsigned long dummy)
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{
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unsigned long now = jiffies;
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int ttl, total;
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struct inet_peer __rcu **stack[PEER_MAXDEPTH];
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total = compute_total();
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if (total >= inet_peer_threshold)
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ttl = inet_peer_minttl;
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else
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ttl = inet_peer_maxttl
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- (inet_peer_maxttl - inet_peer_minttl) / HZ *
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total / inet_peer_threshold * HZ;
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while (!cleanup_once(ttl, stack)) {
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if (jiffies != now)
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break;
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}
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/* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime
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* interval depending on the total number of entries (more entries,
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* less interval). */
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total = compute_total();
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if (total >= inet_peer_threshold)
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peer_periodic_timer.expires = jiffies + inet_peer_gc_mintime;
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else
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peer_periodic_timer.expires = jiffies
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+ inet_peer_gc_maxtime
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- (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ *
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total / inet_peer_threshold * HZ;
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add_timer(&peer_periodic_timer);
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}
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||||
|
||||
void inet_putpeer(struct inet_peer *p)
|
||||
{
|
||||
local_bh_disable();
|
||||
|
||||
if (atomic_dec_and_lock(&p->refcnt, &unused_peers.lock)) {
|
||||
list_add_tail(&p->unused, &unused_peers.list);
|
||||
p->dtime = (__u32)jiffies;
|
||||
spin_unlock(&unused_peers.lock);
|
||||
}
|
||||
|
||||
local_bh_enable();
|
||||
p->dtime = (__u32)jiffies;
|
||||
atomic_dec(&p->refcnt);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(inet_putpeer);
|
||||
|
||||
|
||||
@ -397,20 +397,6 @@ static struct ctl_table ipv4_table[] = {
|
||||
.mode = 0644,
|
||||
.proc_handler = proc_dointvec_jiffies,
|
||||
},
|
||||
{
|
||||
.procname = "inet_peer_gc_mintime",
|
||||
.data = &inet_peer_gc_mintime,
|
||||
.maxlen = sizeof(int),
|
||||
.mode = 0644,
|
||||
.proc_handler = proc_dointvec_jiffies,
|
||||
},
|
||||
{
|
||||
.procname = "inet_peer_gc_maxtime",
|
||||
.data = &inet_peer_gc_maxtime,
|
||||
.maxlen = sizeof(int),
|
||||
.mode = 0644,
|
||||
.proc_handler = proc_dointvec_jiffies,
|
||||
},
|
||||
{
|
||||
.procname = "tcp_orphan_retries",
|
||||
.data = &sysctl_tcp_orphan_retries,
|
||||
|
||||
Loading…
Reference in New Issue
Block a user