rds: Use RCU for the bind lookup searches

The RDS bind lookups are somewhat expensive in terms of CPU
time and locking overhead.  This commit changes them into a
faster RCU based hash tree instead of the rbtrees they were using
before.

On large NUMA systems it is a significant improvement.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 46 insertions, 44 deletions

diff --git a/net/rds/bind.c b/net/rds/bind.c
index a65afff6f4b5..2f6b3fcc79f8 100644
--- a/net/rds/bind.c
+++ b/net/rds/bind.c
@@ -34,45 +34,52 @@
 #include <net/sock.h>
 #include <linux/in.h>
 #include <linux/if_arp.h>
+#include <linux/jhash.h>
 #include "rds.h"
 
-/*
- * XXX this probably still needs more work.. no INADDR_ANY, and rbtrees aren't
- * particularly zippy.
- *
- * This is now called for every incoming frame so we arguably care much more
- * about it than we used to.
- */
-static DEFINE_RWLOCK(rds_bind_lock);
-static struct rb_root rds_bind_tree = RB_ROOT;
+#define BIND_HASH_SIZE 1024
+static struct hlist_head bind_hash_table[BIND_HASH_SIZE];
+static DEFINE_SPINLOCK(rds_bind_lock);
+
+static struct hlist_head *hash_to_bucket(__be32 addr, __be16 port)
+{
+        return bind_hash_table + (jhash_2words((u32)addr, (u32)port, 0) &
+                                  (BIND_HASH_SIZE - 1));
+}
 
-static struct rds_sock *rds_bind_tree_walk(__be32 addr, __be16 port,
-                                           struct rds_sock *insert)
+static struct rds_sock *rds_bind_lookup(__be32 addr, __be16 port,
+                                        struct rds_sock *insert)
 {
-        struct rb_node **p = &rds_bind_tree.rb_node;
-        struct rb_node *parent = NULL;
         struct rds_sock *rs;
+        struct hlist_node *node;
+        struct hlist_head *head = hash_to_bucket(addr, port);
         u64 cmp;
         u64 needle = ((u64)be32_to_cpu(addr) << 32) | be16_to_cpu(port);
 
-        while (*p) {
-                parent = *p;
-                rs = rb_entry(parent, struct rds_sock, rs_bound_node);
-
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(rs, node, head, rs_bound_node) {
                 cmp = ((u64)be32_to_cpu(rs->rs_bound_addr) << 32) |
                       be16_to_cpu(rs->rs_bound_port);
 
-                if (needle < cmp)
-                        p = &(*p)->rb_left;
-                else if (needle > cmp)
-                        p = &(*p)->rb_right;
-                else
+                if (cmp == needle) {
+                        rcu_read_unlock();
                         return rs;
+                }
         }
+        rcu_read_unlock();
 
         if (insert) {
-                rb_link_node(&insert->rs_bound_node, parent, p);
-                rb_insert_color(&insert->rs_bound_node, &rds_bind_tree);
+                /*
+                 * make sure our addr and port are set before
+                 * we are added to the list, other people
+                 * in rcu will find us as soon as the
+                 * hlist_add_head_rcu is done
+                 */
+                insert->rs_bound_addr = addr;
+                insert->rs_bound_port = port;
+                rds_sock_addref(insert);
+
+                hlist_add_head_rcu(&insert->rs_bound_node, head);
         }
         return NULL;
 }
@@ -86,15 +93,13 @@ static struct rds_sock *rds_bind_tree_walk(__be32 addr, __be16 port,
 struct rds_sock *rds_find_bound(__be32 addr, __be16 port)
 {
         struct rds_sock *rs;
-        unsigned long flags;
 
-        read_lock_irqsave(&rds_bind_lock, flags);
-        rs = rds_bind_tree_walk(addr, port, NULL);
+        rs = rds_bind_lookup(addr, port, NULL);
+
         if (rs && !sock_flag(rds_rs_to_sk(rs), SOCK_DEAD))
                 rds_sock_addref(rs);
         else
                 rs = NULL;
-        read_unlock_irqrestore(&rds_bind_lock, flags);
 
         rdsdebug("returning rs %p for %pI4:%u\n", rs, &addr,
                 ntohs(port));
@@ -116,28 +121,21 @@ static int rds_add_bound(struct rds_sock *rs, __be32 addr, __be16 *port)
                 last = rover - 1;
         }
 
-        write_lock_irqsave(&rds_bind_lock, flags);
+        spin_lock_irqsave(&rds_bind_lock, flags);
 
         do {
                 if (rover == 0)
                         rover++;
-                if (!rds_bind_tree_walk(addr, cpu_to_be16(rover), rs)) {
-                        *port = cpu_to_be16(rover);
+                if (!rds_bind_lookup(addr, cpu_to_be16(rover), rs)) {
+                        *port = rs->rs_bound_port;
                         ret = 0;
+                        rdsdebug("rs %p binding to %pI4:%d\n",
+                          rs, &addr, (int)ntohs(*port));
                         break;
                 }
         } while (rover++ != last);
 
-        if (ret == 0)  {
-                rs->rs_bound_addr = addr;
-                rs->rs_bound_port = *port;
-                rds_sock_addref(rs);
-
-                rdsdebug("rs %p binding to %pI4:%d\n",
-                  rs, &addr, (int)ntohs(*port));
-        }
-
-        write_unlock_irqrestore(&rds_bind_lock, flags);
+        spin_unlock_irqrestore(&rds_bind_lock, flags);
 
         return ret;
 }
@@ -146,19 +144,19 @@ void rds_remove_bound(struct rds_sock *rs)
 {
         unsigned long flags;
 
-        write_lock_irqsave(&rds_bind_lock, flags);
+        spin_lock_irqsave(&rds_bind_lock, flags);
 
         if (rs->rs_bound_addr) {
                 rdsdebug("rs %p unbinding from %pI4:%d\n",
                   rs, &rs->rs_bound_addr,
                   ntohs(rs->rs_bound_port));
 
-                rb_erase(&rs->rs_bound_node, &rds_bind_tree);
+                hlist_del_init_rcu(&rs->rs_bound_node);
                 rds_sock_put(rs);
                 rs->rs_bound_addr = 0;
         }
 
-        write_unlock_irqrestore(&rds_bind_lock, flags);
+        spin_unlock_irqrestore(&rds_bind_lock, flags);
 }
 
 int rds_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
@@ -198,5 +196,9 @@ int rds_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 
 out:
         release_sock(sk);
+
+        /* we might have called rds_remove_bound on error */
+        if (ret)
+                synchronize_rcu();
         return ret;
 }