From mboxrd@z Thu Jan 1 00:00:00 1970 From: PJ Waskiewicz Subject: [PATCH] PATCH 2/2 [SCHED 2.6.23-stable]: Check subqueue state before hard_start_xmit Date: Tue, 13 Nov 2007 09:44:56 -0800 Message-ID: <20071113174456.27939.72073.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: davem@davemloft.net Return-path: Received: from mga11.intel.com ([192.55.52.93]:60047 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761523AbXKNAmx (ORCPT ); Tue, 13 Nov 2007 19:42:53 -0500 Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org The only qdiscs that check subqueue state before dequeue'ing are PRIO and RR. The other qdiscs, including the default pfifo_fast qdisc, will allow traffic bound for subqueue 0 through to hard_start_xmit. The check for netif_queue_stopped() is done above in pkt_sched.h, so it is unnecessary for qdisc_restart(). However, if the underlying driver is multiqueue capable, and only sets queue states on subqueues, this will allow packets to enter the driver when it's currently unable to process packets, resulting in expensive requeues and driver entries. This patch re-adds the check for the subqueue status before calling hard_start_xmit, so we can try and avoid the driver entry when the queues are stopped. Signed-off-by: Peter P Waskiewicz Jr --- net/sched/sch_generic.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index c81649c..a35d7ce 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -135,7 +135,7 @@ static inline int qdisc_restart(struct net_device *dev) struct Qdisc *q = dev->qdisc; struct sk_buff *skb; unsigned lockless; - int ret; + int ret = NETDEV_TX_BUSY; /* Dequeue packet */ if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL)) @@ -158,7 +158,8 @@ static inline int qdisc_restart(struct net_device *dev) /* And release queue */ spin_unlock(&dev->queue_lock); - ret = dev_hard_start_xmit(skb, dev); + if (!netif_subqueue_stopped(dev, skb->queue_mapping)) + ret = dev_hard_start_xmit(skb, dev); if (!lockless) netif_tx_unlock(dev);