Commit 270acefa authored Nov 05, 2008 by Eric Dumazet Committed by David S. Miller Nov 05, 2008

net: sk_free_datagram() should use sk_mem_reclaim_partial()



I noticed a contention on udp_memory_allocated on regular UDP applications.

While tcp_memory_allocated is seldom used, it appears each incoming UDP frame
is currently touching udp_memory_allocated when queued, and when received by
application.

One possible solution is to use sk_mem_reclaim_partial() instead of
sk_mem_reclaim(), so that we keep a small reserve (less than one page)
of memory for each UDP socket.

We did something very similar on TCP side in commit
9993e7d3
([TCP]: Do not purge sk_forward_alloc entirely in tcp_delack_timer())

A more complex solution would need to convert prot->memory_allocated to
use a percpu_counter with batches of 64 or 128 pages.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent d99a7bd2

net/core/datagram.c

+2 −3

Original line number	Original line	Diff line number	Diff line
	@@ -209,7 +209,7 @@ struct sk_buff skb_recv_datagram(struct sock sk, unsigned flags,
	void skb_free_datagram(struct sock sk, struct sk_buff skb)		void skb_free_datagram(struct sock sk, struct sk_buff skb)
	{		{
	kfree_skb(skb);		kfree_skb(skb);
	sk_mem_reclaim(sk);		sk_mem_reclaim_partial(sk);
	}		}

	/**		/**
	@@ -248,8 +248,7 @@ int skb_kill_datagram(struct sock sk, struct sk_buff skb, unsigned int flags)
	spin_unlock_bh(&sk->sk_receive_queue.lock);		spin_unlock_bh(&sk->sk_receive_queue.lock);
	}		}

	kfree_skb(skb);		skb_free_datagram(sk, skb);
	sk_mem_reclaim(sk);
	return err;		return err;
	}		}