neigh: Protect neigh->ha[] with a seqlock

Add a seqlock in struct neighbour to protect neigh->ha[], and avoid
dirtying neighbour in stress situation (many different flows / dsts)

Dirtying takes place because of read_lock(&n->lock) and n->used writes.

Switching to a seqlock, and writing n->used only on jiffies changes
permits less dirtying.

Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2010-10-07 10:44:07 +00:00 • committed by David S. Miller
commit 0ed8ddf404
4 changed files with 51 additions and 26 deletions

View file

@ -502,10 +502,8 @@ int arp_find(unsigned char *haddr, struct sk_buff *skb)
if (n) {
n->used = jiffies;
if (n->nud_state&NUD_VALID || neigh_event_send(n, skb) == 0) {
read_lock_bh(&n->lock);
memcpy(haddr, n->ha, dev->addr_len);
read_unlock_bh(&n->lock);
if (n->nud_state & NUD_VALID || neigh_event_send(n, skb) == 0) {
neigh_ha_snapshot(haddr, n, dev);
neigh_release(n);
return 0;
}