From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] tun: do not put self in waitq if doing a nonblock read Date: Thu, 09 Jun 2011 00:27:21 -0700 (PDT) Message-ID: <20110609.002721.963829441380663942.davem@davemloft.net> References: <20110608234606.8681.19932.stgit@localhost6.localdomain6> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jasowang@redhat.com, kvm@vger.kernel.org, mst@redhat.com To: akong@redhat.com Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:53183 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753501Ab1FIH1Z (ORCPT ); Thu, 9 Jun 2011 03:27:25 -0400 In-Reply-To: <20110608234606.8681.19932.stgit@localhost6.localdomain6> Sender: netdev-owner@vger.kernel.org List-ID: From: Amos Kong Date: Thu, 09 Jun 2011 07:46:06 +0800 > Perf shows a relatively high rate (about 8%) race in > spin_lock_irqsave() when doing netperf between external host and > guest. It's mainly becuase the lock contention between the > tun_do_read() and tun_xmit_skb(), so this patch do not put self into > waitqueue to reduce this kind of race. After this patch, it drops to > 4%. > > Signed-off-by: Jason Wang > Signed-off-by: Amos Kong Applied, thanks.