From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [RFC PATCH] net: add additional lock to qdisc to increase enqueue/dequeue fairness Date: Tue, 23 Mar 2010 14:45:12 -0700 (PDT) Message-ID: <20100323.144512.140757007.davem@davemloft.net> References: <20100323202553.21598.10754.stgit@gitlad.jf.intel.com> <1269377667.2915.25.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: alexander.h.duyck@intel.com, netdev@vger.kernel.org To: eric.dumazet@gmail.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:55102 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754106Ab0CWVou (ORCPT ); Tue, 23 Mar 2010 17:44:50 -0400 In-Reply-To: <1269377667.2915.25.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Tue, 23 Mar 2010 21:54:27 +0100 > Quite frankly, the real problem in this case is not the reduced > throughput, but fact that one cpu can stay a long time doing the xmits > to device, of skb queued by other cpus. This can hurt latencies a lot, > for real time threads for example... > > I wonder if ticket spinlocks are not the problem. Maybe we want a > variant of spinlocks, so that cpu doing transmits can get the lock > before other cpus... I want to note that things operate the way they do now intentionally. Herbert Xu and Jamal Hadi Salim were active in this area about 4 years ago.