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RDS: Use per-bucket rw lock for bind hash-table 

One global lock protecting hash-tables with 1024 buckets isn't
efficient and it shows up in a massive systems with truck
loads of RDS sockets serving multiple databases. The
perf data clearly highlights the contention on the rw
lock in these massive workloads.

When the contention gets worse, the code gets into a state where
it decides to back off on the lock. So while it has disabled interrupts,
it sits and backs off on this lock get. This causes the system to
become sluggish and eventually all sorts of bad things happen.

The simple fix is to move the lock into the hash bucket and
use per-bucket lock to improve the scalability.

Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
This commit is contained in:
Santosh Shilimkar 2014-02-11 19:34:25 -08:00 committed by Santosh Shilimkar
parent 2812695988
commit 9b9acde7e8
3 changed files with 36 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/rds/af_rds.c
View File

@ -582,6 +582,8 @@ static int rds_init(void)
{
int ret;
rds_bind_lock_init();
ret = rds_conn_init();
if (ret)
goto out;

49
net/rds/bind.c
View File

@ -38,22 +38,27 @@
#include <linux/ratelimit.h>
#include "rds.h"
#define BIND_HASH_SIZE 1024
static struct hlist_head bind_hash_table[BIND_HASH_SIZE];
static DEFINE_RWLOCK(rds_bind_lock);
struct bind_bucket {
rwlock_t lock;
struct hlist_head head;
};
static struct hlist_head *hash_to_bucket(__be32 addr, __be16 port)
#define BIND_HASH_SIZE 1024
static struct bind_bucket bind_hash_table[BIND_HASH_SIZE];
static struct bind_bucket *hash_to_bucket(__be32 addr, __be16 port)
{
return bind_hash_table + (jhash_2words((u32)addr, (u32)port, 0) &
(BIND_HASH_SIZE - 1));
}
/* must hold either read or write lock (write lock for insert != NULL) */
static struct rds_sock *rds_bind_lookup(__be32 addr, __be16 port,
static struct rds_sock *rds_bind_lookup(struct bind_bucket *bucket,
__be32 addr, __be16 port,
struct rds_sock *insert)
{
struct rds_sock *rs;
struct hlist_head *head = hash_to_bucket(addr, port);
struct hlist_head *head = &bucket->head;
u64 cmp;
u64 needle = ((u64)be32_to_cpu(addr) << 32) | be16_to_cpu(port);
@ -91,10 +96,11 @@ struct rds_sock *rds_find_bound(__be32 addr, __be16 port)
{
struct rds_sock *rs;
unsigned long flags;
struct bind_bucket *bucket = hash_to_bucket(addr, port);
read_lock_irqsave(&rds_bind_lock, flags);
rs = rds_bind_lookup(addr, port, NULL);
read_unlock_irqrestore(&rds_bind_lock, flags);
read_lock_irqsave(&bucket->lock, flags);
rs = rds_bind_lookup(bucket, addr, port, NULL);
read_unlock_irqrestore(&bucket->lock, flags);
if (rs && sock_flag(rds_rs_to_sk(rs), SOCK_DEAD)) {
rds_sock_put(rs);
@ -113,6 +119,7 @@ static int rds_add_bound(struct rds_sock *rs, __be32 addr, __be16 *port)
unsigned long flags;
int ret = -EADDRINUSE;
u16 rover, last;
struct bind_bucket *bucket;
if (*port != 0) {
rover = be16_to_cpu(*port);
@ -122,13 +129,15 @@ static int rds_add_bound(struct rds_sock *rs, __be32 addr, __be16 *port)
last = rover - 1;
}
write_lock_irqsave(&rds_bind_lock, flags);
do {
struct rds_sock *rrs;
if (rover == 0)
rover++;
rrs = rds_bind_lookup(addr, cpu_to_be16(rover), rs);
bucket = hash_to_bucket(addr, cpu_to_be16(rover));
write_lock_irqsave(&bucket->lock, flags);
rrs = rds_bind_lookup(bucket, addr, cpu_to_be16(rover), rs);
write_unlock_irqrestore(&bucket->lock, flags);
if (!rrs) {
*port = rs->rs_bound_port;
ret = 0;
@ -140,16 +149,16 @@ static int rds_add_bound(struct rds_sock *rs, __be32 addr, __be16 *port)
}
} while (rover++ != last);
write_unlock_irqrestore(&rds_bind_lock, flags);
return ret;
}
void rds_remove_bound(struct rds_sock *rs)
{
unsigned long flags;
struct bind_bucket *bucket =
hash_to_bucket(rs->rs_bound_addr, rs->rs_bound_port);
write_lock_irqsave(&rds_bind_lock, flags);
write_lock_irqsave(&bucket->lock, flags);
if (rs->rs_bound_addr) {
rdsdebug("rs %p unbinding from %pI4:%d\n",
@ -161,7 +170,7 @@ void rds_remove_bound(struct rds_sock *rs)
rs->rs_bound_addr = 0;
}
write_unlock_irqrestore(&rds_bind_lock, flags);
write_unlock_irqrestore(&bucket->lock, flags);
}
int rds_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
@ -207,3 +216,11 @@ out:
release_sock(sk);
return ret;
}
void rds_bind_lock_init(void)
{
int i;
for (i = 0; i < BIND_HASH_SIZE; i++)
rwlock_init(&bind_hash_table[i].lock);
}

1
net/rds/rds.h
View File

@ -603,6 +603,7 @@ extern wait_queue_head_t rds_poll_waitq;
int rds_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len);
void rds_remove_bound(struct rds_sock *rs);
struct rds_sock *rds_find_bound(__be32 addr, __be16 port);
void rds_bind_lock_init(void);
/* cong.c */
int rds_cong_get_maps(struct rds_connection *conn);