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udp: be less conservative with sock rmem accounting

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Before commit 850cbaddb5 ("udp: use it's own memory accounting
schema"), the udp protocol allowed sk_rmem_alloc to grow beyond
the rcvbuf by the whole current packet's truesize. After said commit
we allow sk_rmem_alloc to exceed the rcvbuf only if the receive queue
is empty. As reported by Jesper this cause a performance regression
for some (small) values of rcvbuf.

This commit is intended to fix the regression restoring the old
handling of the rcvbuf limit.

Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Fixes: 850cbaddb5 ("udp: use it's own memory accounting schema")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2016-12-02 17:35:49 +01:00 committed by David S. Miller
parent 12efa1fa43
commit 363dc73aca
1 changed files with 2 additions and 2 deletions
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4
net/ipv4/udp.c
View file

@ -1205,14 +1205,14 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
* queue is full; always allow at least a packet
*/
rmem = atomic_read(&sk->sk_rmem_alloc);
if (rmem && (rmem + size > sk->sk_rcvbuf))
if (rmem > sk->sk_rcvbuf)
goto drop;
/* we drop only if the receive buf is full and the receive
* queue contains some other skb
*/
rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
if ((rmem > sk->sk_rcvbuf) && (rmem > size))
if (rmem > (size + sk->sk_rcvbuf))
goto uncharge_drop;
spin_lock(&list->lock);