From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krishna Kumar Subject: [PATCH 2/2] qdisc_restart - couple of optimizations. Date: Wed, 13 Jun 2007 14:10:49 +0530 Message-ID: <1181724049.10679.31.camel@localhost.localdomain> Reply-To: kumarkr@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit To: davem@davemloft.net, jamal@cyberus.ca, herbert@gondor.apana.org.au, peter.p.waskiewicz.jr@intel.com, tgraf@suug.ch, kaber@trash.net, netdev@vger.kernel.org Return-path: Received: from ausmtp04.au.ibm.com ([202.81.18.152]:41736 "EHLO ausmtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755092AbXFMIk7 (ORCPT ); Wed, 13 Jun 2007 04:40:59 -0400 Received: from sd0109e.au.ibm.com (d23rh905.au.ibm.com [202.81.18.225]) by ausmtp04.au.ibm.com (8.13.8/8.13.8) with ESMTP id l5D923Vm186628 for ; Wed, 13 Jun 2007 19:02:03 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.250.242]) by sd0109e.au.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l5D8hwGb131252 for ; Wed, 13 Jun 2007 18:44:05 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l5D8eLn2015253 for ; Wed, 13 Jun 2007 18:40:22 +1000 Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org - netif_queue_stopped need not be called inside qdisc_restart as it has been called already in qdisc_run() before the first skb is sent, and in __qdisc_run() after each intermediate skb is sent (note : we are the only sender, so the queue cannot get stopped while the tx lock was got in the ~LLTX case). - BUG_ON((int) q->q.qlen < 0) was a relic from old times when -1 meant more packets are available, and __qdisc_run used to loop when qdisc_restart() returned -1. During those days, it was necessary to make sure that qlen is never less than zero, since __qdisc_run would get into an infinite loop if no packets are on the queue and this bug in qdisc was there (and worse - no more skbs could ever get queue'd as we hold the queue lock too). With Herbert's recent change to return values, this check is not required. Hopefully Herbert can validate this change. If at all this is required, it should be added to skb_dequeue (in failure case), and not to qdisc_qlen. Signed-off-by: Krishna Kumar --- diff -ruNp org/net/sched/sch_generic.c new/net/sched/sch_generic.c --- org/net/sched/sch_generic.c 2007-06-11 13:12:11.000000000 +0530 +++ new/net/sched/sch_generic.c 2007-06-11 15:37:48.000000000 +0530 @@ -61,7 +61,6 @@ void qdisc_unlock_tree(struct net_device static inline int qdisc_qlen(struct Qdisc *q) { - BUG_ON((int) q->q.qlen < 0); return q->q.qlen; } @@ -167,9 +166,7 @@ static inline int qdisc_restart(struct n /* And release queue */ spin_unlock(&dev->queue_lock); - ret = NETDEV_TX_BUSY; - if (!netif_queue_stopped(dev)) - ret = dev_hard_start_xmit(skb, dev); + ret = dev_hard_start_xmit(skb, dev); if (!lockless) netif_tx_unlock(dev);