rds: Use RCU for the bind lookup searches
Chris Mason [Tue, 11 May 2010 22:09:45 +0000 (15:09 -0700)]
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>

net/rds/af_rds.c
net/rds/bind.c
net/rds/ib_rdma.c
net/rds/rds.h

index ef09340..f16d2a9 100644 (file)
@@ -72,7 +72,15 @@ static int rds_release(struct socket *sock)
         * with the socket. */
        rds_clear_recv_queue(rs);
        rds_cong_remove_socket(rs);
+
+       /*
+        * the binding lookup hash uses rcu, we need to
+        * make sure we sychronize_rcu before we free our
+        * entry
+        */
        rds_remove_bound(rs);
+       synchronize_rcu();
+
        rds_send_drop_to(rs, NULL);
        rds_rdma_drop_keys(rs);
        rds_notify_queue_get(rs, NULL);
index a65afff..2f6b3fc 100644 (file)
 #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;
 }
index cc341cd..4ba01b9 100644 (file)
@@ -303,6 +303,8 @@ static struct rds_ib_mr *rds_ib_alloc_fmr(struct rds_ib_device *rds_ibdev)
                goto out_no_cigar;
        }
 
+       memset(ibmr, 0, sizeof(*ibmr));
+
        ibmr->fmr = ib_alloc_fmr(rds_ibdev->pd,
                        (IB_ACCESS_LOCAL_WRITE |
                         IB_ACCESS_REMOTE_READ |
index c22bd7b..241a085 100644 (file)
@@ -452,7 +452,7 @@ struct rds_sock {
         * bound_addr used for both incoming and outgoing, no INADDR_ANY
         * support.
         */
-       struct rb_node          rs_bound_node;
+       struct hlist_node       rs_bound_node;
        __be32                  rs_bound_addr;
        __be32                  rs_conn_addr;
        __be16                  rs_bound_port;