Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932899Ab3D2TKx (ORCPT ); Mon, 29 Apr 2013 15:10:53 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60989 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757834Ab3D2TDZ (ORCPT ); Mon, 29 Apr 2013 15:03:25 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasily Averin , Alexey Kuznetsov , Eric Dumazet , "David S. Miller" Subject: [ 04/30] cbq: incorrect processing of high limits Date: Mon, 29 Apr 2013 12:02:28 -0700 Message-Id: <20130429184355.789332528@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130429184355.299556377@linuxfoundation.org> References: <20130429184355.299556377@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1727 Lines: 59 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vasily Averin [ Upstream commit f0f6ee1f70c4eaab9d52cf7d255df4bd89f8d1c2 ] currently cbq works incorrectly for limits > 10% real link bandwidth, and practically does not work for limits > 50% real link bandwidth. Below are results of experiments taken on 1 Gbit link In shaper | Actual Result -----------+--------------- 100M | 108 Mbps 200M | 244 Mbps 300M | 412 Mbps 500M | 893 Mbps This happen because of q->now changes incorrectly in cbq_dequeue(): when it is called before real end of packet transmitting, L2T is greater than real time delay, q_now gets an extra boost but never compensate it. To fix this problem we prevent change of q->now until its synchronization with real time. Signed-off-by: Vasily Averin Reviewed-by: Alexey Kuznetsov Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_cbq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/net/sched/sch_cbq.c +++ b/net/sched/sch_cbq.c @@ -963,8 +963,11 @@ cbq_dequeue(struct Qdisc *sch) cbq_update(q); if ((incr -= incr2) < 0) incr = 0; + q->now += incr; + } else { + if (now > q->now) + q->now = now; } - q->now += incr; q->now_rt = now; for (;;) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/