Commit 363dc73a authored Dec 02, 2016 by Paolo Abeni Committed by David S. Miller Dec 03, 2016

udp: be less conservative with sock rmem accounting



Before commit 850cbadd ("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: 850cbadd ("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>

parent 12efa1fa

net/ipv4/udp.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);

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