From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: [PATCH 3/3] netlink: wake up netlink listeners sooner Date: Wed, 21 Dec 2011 13:49:44 -0800 Message-ID: <20111221134944.52223cdf@nehalam.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:50874 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753774Ab1LUVuA (ORCPT ); Wed, 21 Dec 2011 16:50:00 -0500 Sender: netdev-owner@vger.kernel.org List-ID: A netlink listening task (such as Quagga/zebra) can easily get overrun when lots of events happen such as a link state transition with full BGP route table. This happens because the sender does not yield to the receiver (unless socket queue is full). The problem is exacerbated because it is typical for listeners to set large receive buffer to attempt to keep up. This patch changes it to yield sooner at halfway instead. Still not a cure-all for listener overrun if listener is slow, but works much reliably. Signed-off-by: Stephen Hemminger --- a/net/netlink/af_netlink.c 2011-12-20 10:25:19.364247598 -0800 +++ b/net/netlink/af_netlink.c 2011-12-20 10:25:46.756570010 -0800 @@ -960,7 +960,7 @@ static int netlink_broadcast_deliver(str skb_set_owner_r(skb, sk); skb_queue_tail(&sk->sk_receive_queue, skb); sk->sk_data_ready(sk, skb->len); - return atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf; + return atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf / 2; } return -1; }