From patchwork Fri Mar 22 15:01:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Abeni X-Patchwork-Id: 1061292 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@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; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 44Qn3f4F3Tz9sRd for ; Sat, 23 Mar 2019 02:03:42 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729582AbfCVPDl (ORCPT ); Fri, 22 Mar 2019 11:03:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56912 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729566AbfCVPDl (ORCPT ); Fri, 22 Mar 2019 11:03:41 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A7E9A356FF; Fri, 22 Mar 2019 15:03:40 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.32.181.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id 89F195C57E; Fri, 22 Mar 2019 15:03:39 +0000 (UTC) From: Paolo Abeni To: netdev@vger.kernel.org Cc: "David S. Miller" , Eric Dumazet , John Fastabend , Ivan Vecera Subject: [PATCH net-next v3 2/2] net: dev: introduce support for sch BYPASS for lockless qdisc Date: Fri, 22 Mar 2019 16:01:56 +0100 Message-Id: <309f53a89c097a186ec37c841bb5d986ecf0ce3e.1553263445.git.pabeni@redhat.com> In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 22 Mar 2019 15:03:40 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org With commit c5ad119fb6c0 ("net: sched: pfifo_fast use skb_array") pfifo_fast no longer benefit from the TCQ_F_CAN_BYPASS optimization. Due to retpolines the cost of the enqueue()/dequeue() pair has become relevant and we observe measurable regression for the uncontended scenario when the packet-rate is below line rate. After commit 46b1c18f9deb ("net: sched: put back q.qlen into a single location") we can check for empty qdisc with a reasonably fast operation even for nolock qdiscs. This change extends TCQ_F_CAN_BYPASS support to nolock qdisc. The new chunk of code mirrors closely the existing one for traditional qdisc, leveraging a newly introduced helper to read atomically the qdisc length. Tested with pktgen in queue xmit mode, with pfifo_fast, a MQ device, and MQ root qdisc: threads vanilla patched kpps kpps 1 2465 2889 2 4304 5188 4 7898 9589 Same as above, but with a single queue device: threads vanilla patched kpps kpps 1 2556 2827 2 2900 2900 4 5000 5000 8 4700 4700 No mesaurable changes in the contended scenarios, and more 10% improvement in the uncontended ones. v1 -> v2: - rebased after flag name change Signed-off-by: Paolo Abeni Tested-by: Ivan Vecera Reviewed-by: Eric Dumazet Reviewed-by: Ivan Vecera --- net/core/dev.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index 2b67f2aa59dd..e6cf39a9d3c5 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3468,6 +3468,15 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) { __qdisc_drop(skb, &to_free); rc = NET_XMIT_DROP; + } else if ((q->flags & TCQ_F_CAN_BYPASS) && q->empty && + qdisc_run_begin(q)) { + qdisc_bstats_cpu_update(q, skb); + + if (sch_direct_xmit(skb, q, dev, txq, NULL, true)) + __qdisc_run(q); + + qdisc_run_end(q); + rc = NET_XMIT_SUCCESS; } else { rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK; qdisc_run(q);