[net-next 1/1] tipc: optimize function tipc_node_timeout()

[net-next 1/1] tipc: optimize function tipc_node_timeout()

[Jon Maloy]

From: Tung Nguyen <tung.q.nguyen@dektech.com.au>

In single-link usage, the function tipc_node_timeout() still iterates
over the whole link array to handle each link. Given that the maximum
number of bearers are 3, there are 2 redundant iterations with lock
grab/release. Since this function is executing very frequently it makes
sense to optimize it.

This commit adds conditional checking to exit from the loop if the
known number of configured links has already been accessed.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
---
 net/tipc/node.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 6a44eb8..8972ca1 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -551,21 +551,23 @@ static void tipc_node_timeout(struct timer_list *t)
 	struct tipc_node *n = from_timer(n, t, timer);
 	struct tipc_link_entry *le;
 	struct sk_buff_head xmitq;
+	int remains = n->link_cnt;
 	int bearer_id;
 	int rc = 0;
 
 	__skb_queue_head_init(&xmitq);
 
-	for (bearer_id = 0; bearer_id < MAX_BEARERS; bearer_id++) {
+	for (bearer_id = 0; remains && (bearer_id < MAX_BEARERS); bearer_id++) {
 		tipc_node_read_lock(n);
 		le = &n->links[bearer_id];
-		spin_lock_bh(&le->lock);
 		if (le->link) {
+			spin_lock_bh(&le->lock);
 			/* Link tolerance may change asynchronously: */
 			tipc_node_calculate_timer(n, le->link);
 			rc = tipc_link_timeout(le->link, &xmitq);
+			spin_unlock_bh(&le->lock);
+			remains--;
 		}
-		spin_unlock_bh(&le->lock);
 		tipc_node_read_unlock(n);
 		tipc_bearer_xmit(n->net, bearer_id, &xmitq, &le->maddr);
 		if (rc & TIPC_LINK_DOWN_EVT)
-- 
2.1.4

Re: [net-next 1/1] tipc: optimize function tipc_node_timeout()

[David Miller]

From: Jon Maloy <jon.maloy@ericsson.com>
Date: Thu, 28 Jun 2018 22:39:25 +0200

> From: Tung Nguyen <tung.q.nguyen@dektech.com.au>
> 
> In single-link usage, the function tipc_node_timeout() still iterates
> over the whole link array to handle each link. Given that the maximum
> number of bearers are 3, there are 2 redundant iterations with lock
> grab/release. Since this function is executing very frequently it makes
> sense to optimize it.
> 
> This commit adds conditional checking to exit from the loop if the
> known number of configured links has already been accessed.
> 
> Acked-by: Ying Xue <ying.xue@windriver.com>
> Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>

Applied.