From patchwork Mon Aug 21 08:14:14 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Konstantin Khlebnikov X-Patchwork-Id: 803885 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="hoBtZYpF"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3xbRL75Wlyz9tWB for ; Mon, 21 Aug 2017 18:14:23 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752071AbdHUIOU (ORCPT ); Mon, 21 Aug 2017 04:14:20 -0400 Received: from forwardcorp1o.cmail.yandex.net ([37.9.109.47]:55701 "EHLO forwardcorp1o.cmail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751750AbdHUIOT (ORCPT ); Mon, 21 Aug 2017 04:14:19 -0400 Received: from smtpcorp1o.mail.yandex.net (smtpcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::30]) by forwardcorp1o.cmail.yandex.net (Yandex) with ESMTP id 380EB20B54; Mon, 21 Aug 2017 11:14:17 +0300 (MSK) Received: from smtpcorp1o.mail.yandex.net (localhost.localdomain [127.0.0.1]) by smtpcorp1o.mail.yandex.net (Yandex) with ESMTP id 35A112440C28; Mon, 21 Aug 2017 11:14:17 +0300 (MSK) Received: from unknown (unknown [2a02:6b8:0:6::1:c]) by smtpcorp1o.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id HuxCHlur3e-EHQ4QYvf; Mon, 21 Aug 2017 11:14:17 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1503303257; bh=qBfZLUu9X9jmlaccRHc0ro4VCDesl5ANOhwrtvB+FcA=; h=Subject:From:To:Cc:Date:Message-ID; b=hoBtZYpFp/6WjTNUk4V/A+riQ2TpjF20S6rFWAKvxVHbZVGdRkxsFuuR+837yyruL avpcJXJ15aRA+7DufewNhunPUVRHxj9MdTkb9lfe3gFwIm3gh3yreuMGNEmY54Ucuv xr0u21izL9PTvAuPFLbLV6pVYzLsKI8fH11Vdp5o= Authentication-Results: smtpcorp1o.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Subject: [PATCH RFC] net_sched/codel: do not defer queue length update From: Konstantin Khlebnikov To: netdev@vger.kernel.org, "David S. Miller" Cc: Cong Wang , Eric Dumazet , Jiri Pirko Date: Mon, 21 Aug 2017 11:14:14 +0300 Message-ID: <150330325401.155105.30496752582836861.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When codel wants to drop last packet in ->dequeue() it cannot call qdisc_tree_reduce_backlog() right away - it will notify parent qdisc about zero qlen and HTB/HFSC will deactivate class. The same class will be deactivated second time by caller of ->dequeue(). Currently codel and fq_codel defer update. This triggers warning in HFSC when it's qlen != 0 but there is no active classes. This patch update parent queue length immediately: just temporary increase qlen around qdisc_tree_reduce_backlog() to prevent first class deactivation if we have skb to return. This might open another problem in HFSC - now operation peek could fail and deactivate parent class. Signed-off-by: Konstantin Khlebnikov Link: https://bugzilla.kernel.org/show_bug.cgi?id=109581 --- net/sched/sch_codel.c | 14 ++++++++++---- net/sched/sch_fq_codel.c | 24 +++++++++++++++--------- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c index c518a1efcb9d..e8194e455efe 100644 --- a/net/sched/sch_codel.c +++ b/net/sched/sch_codel.c @@ -95,11 +95,17 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch) &q->stats, qdisc_pkt_len, codel_get_enqueue_time, drop_func, dequeue_func); - /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0, - * or HTB crashes. Defer it for next round. + /* If our qlen is 0 qdisc_tree_reduce_backlog() will deactivate + * parent class, dequeue in parent qdisc will do the same if we + * return skb. Temporary increment qlen if we have skb. */ - if (q->stats.drop_count && sch->q.qlen) { - qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len); + if (q->stats.drop_count) { + if (skb) + sch->q.qlen++; + qdisc_tree_reduce_backlog(sch, q->stats.drop_count, + q->stats.drop_len); + if (skb) + sch->q.qlen--; q->stats.drop_count = 0; q->stats.drop_len = 0; } diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index 337f2d6d81e4..4048790a8c99 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -316,6 +316,21 @@ static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch) flow->dropped += q->cstats.drop_count - prev_drop_count; flow->dropped += q->cstats.ecn_mark - prev_ecn_mark; + /* If our qlen is 0 qdisc_tree_reduce_backlog() will deactivate + * parent class, dequeue in parent qdisc will do the same if we + * return skb. Temporary increment qlen if we have skb. + */ + if (q->cstats.drop_count) { + if (skb) + sch->q.qlen++; + qdisc_tree_reduce_backlog(sch, q->cstats.drop_count, + q->cstats.drop_len); + if (skb) + sch->q.qlen--; + q->cstats.drop_count = 0; + q->cstats.drop_len = 0; + } + if (!skb) { /* force a pass through old_flows to prevent starvation */ if ((head == &q->new_flows) && !list_empty(&q->old_flows)) @@ -326,15 +341,6 @@ static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch) } qdisc_bstats_update(sch, skb); flow->deficit -= qdisc_pkt_len(skb); - /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0, - * or HTB crashes. Defer it for next round. - */ - if (q->cstats.drop_count && sch->q.qlen) { - qdisc_tree_reduce_backlog(sch, q->cstats.drop_count, - q->cstats.drop_len); - q->cstats.drop_count = 0; - q->cstats.drop_len = 0; - } return skb; }