From patchwork Mon May 23 21:02:42 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 97060 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 4D256B6FBB for ; Tue, 24 May 2011 07:03:32 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030388Ab1EWVDG (ORCPT ); Mon, 23 May 2011 17:03:06 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:60760 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030336Ab1EWVCq (ORCPT ); Mon, 23 May 2011 17:02:46 -0400 Received: by wya21 with SMTP id 21so4515850wya.19 for ; Mon, 23 May 2011 14:02:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:from:to:cc:content-type:date:message-id :mime-version:x-mailer:content-transfer-encoding; bh=1+fygE4GZBk5F93ihiJjItS9vvDxbTZhPd0Yc9G9PLA=; b=svbXe8q4DOLJETgdeNYCQSnUb3rPZ4yaxoJDXL8bHeyegeYZmOGIRkcNRwGaUfC5Hj BIwiPgJ3iL0ehHAT8D64Eju/BPPL/b9+FkAak6DODncSXizYbfcAcw+dsghPXKDBS9RO m6TK16YdQx2WyrYIOD7DTi65Dlveh+tr6+Qbg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:content-type:date:message-id:mime-version :x-mailer:content-transfer-encoding; b=LCanNUyf793pCTELZxKZBDCBHTg/VjciAwAX3CMBPiz/y37mCdoj/Le2rCbYzKauSb 6b36rqfuNn0KwS62VwtKatDpVdWutFCT+/VjQWRhi5NKfRzxRm3t0xsXIGJIKCfK9M72 IJS7s4NPmln0FZfPa2c+N64Ez/+0GY9qoSukk= Received: by 10.227.11.203 with SMTP id u11mr143775wbu.77.1306184565582; Mon, 23 May 2011 14:02:45 -0700 (PDT) Received: from [10.150.51.210] (gw0.net.jmsp.net [212.23.165.14]) by mx.google.com with ESMTPS id l24sm4346103wbc.13.2011.05.23.14.02.43 (version=SSLv3 cipher=OTHER); Mon, 23 May 2011 14:02:44 -0700 (PDT) Subject: [PATCH] sch_sfq: avoid giving spurious NET_XMIT_CN signals From: Eric Dumazet To: David Miller Cc: netdev , Patrick McHardy , Jarek Poplawski , Jamal Hadi Salim , Stephen Hemminger Date: Mon, 23 May 2011 23:02:42 +0200 Message-ID: <1306184562.2638.14.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org While chasing a possible net_sched bug, I found that IP fragments have litle chance to pass a congestioned SFQ qdisc : - Say SFQ qdisc is full because one flow is non responsive. - ip_fragment() wants to send two fragments belonging to an idle flow. - sfq_enqueue() queues first packet, but see queue limit reached : - sfq_enqueue() drops one packet from 'big consumer', and returns NET_XMIT_CN. - ip_fragment() cancel remaining fragments. This patch restores fairness, making sure we return NET_XMIT_CN only if we dropped a packet from the same flow. Signed-off-by: Eric Dumazet CC: Patrick McHardy CC: Jarek Poplawski CC: Jamal Hadi Salim CC: Stephen Hemminger --- net/sched/sch_sfq.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c index 7ef87f9..b1d00f8 100644 --- a/net/sched/sch_sfq.c +++ b/net/sched/sch_sfq.c @@ -361,7 +361,7 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) { struct sfq_sched_data *q = qdisc_priv(sch); unsigned int hash; - sfq_index x; + sfq_index x, qlen; struct sfq_slot *slot; int uninitialized_var(ret); @@ -405,8 +405,12 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) if (++sch->q.qlen <= q->limit) return NET_XMIT_SUCCESS; + qlen = slot->qlen; sfq_drop(sch); - return NET_XMIT_CN; + /* Return Congestion Notification only if we dropped a packet + * from this flow. + */ + return (qlen != slot->qlen) ? NET_XMIT_CN : NET_XMIT_SUCCESS; } static struct sk_buff *