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
9993e7d313e80bdc005d09c7def91903e0068f07
([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>

diff --git a/net/core/datagram.c b/net/core/datagram.c
index ee63184..5e2ac0c 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -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)
 {
        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);
        }
 
-       kfree_skb(skb);
-       sk_mem_reclaim(sk);
+       skb_free_datagram(sk, skb);
        return err;
 }