From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9ED9CC433DF for ; Wed, 8 Jul 2020 22:29:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 745F720772 for ; Wed, 8 Jul 2020 22:29:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CXg4QWnd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726117AbgGHW30 (ORCPT ); Wed, 8 Jul 2020 18:29:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725903AbgGHW3Z (ORCPT ); Wed, 8 Jul 2020 18:29:25 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B42E7C061A0B for ; Wed, 8 Jul 2020 15:29:25 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id w2so23218pgg.10 for ; Wed, 08 Jul 2020 15:29:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=12moK1imdj5+Kv/e3/hbcbYfop44kWkDJPAIBfHMbzI=; b=CXg4QWndiZ1ndhPGVVWhJ5xO8x4IFFqaZtXMAA5HQ7jdlSlmMPKhamADZH9vlVJeyH +FSpX7xcXLkSBX6rE4wz7icw/9dtyNmVPyxnxMaFvXN2g6iUs1qOVLesQuf4LB8m9bMo FxVpjOb8Oxo6nQ0stvPkJJmD6xoWtGubU5+PZOQnphiyJikGUQVtxRbg9DCcot+VCsr4 h6f0jkuBufnTt2QgF4LLy+YhYnstmlje7PVX6TwLNK/91Glkdtp8qvpa2johh24x32Lo MatV0MoOZIOEDzdVUi9u6V4g9rqeGB3P5XF/twMDQok0nIYU/QC/cnpR66kAo3W0ZTUt uFKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=12moK1imdj5+Kv/e3/hbcbYfop44kWkDJPAIBfHMbzI=; b=GB6LvDacs2ixMaoTqMmJTMqDFq5KEPEAwteK56/CLXAcJieXgjotaUT8Xlh3a6W/TN 7jTnzDDoerdsLwAcmQKrQAfht4FO13dVSPyN84LXIKsfZrz9u+/CUnj2hC4i8Zk5SWbM B28kVZA2F23GjT2QuIDYQun0p4m2hzEjZaNIfMAV7gjTMbWzlZihyUg3g0VO0CQgD4fH BLPyunUPj9pFLaAsVJkUBOrGFyMTn+r07JF2uvnHR1ZjHcROh0nkR2cJmtFNrtsdCKhs XMWmH4eWNsovY+0yxr6ab6eYq8vnA8dYT7/w5XHy0WmnHfuW9BB1dnEb5+L1fGep+efa 70Bg== X-Gm-Message-State: AOAM531zn8otiuHN2tjopQjHLDlGbwTJJmEgSojArPgUTFqZQdaY77f0 7fTxA4dOKgRHidLBUjWEa7Q2IeYT X-Google-Smtp-Source: ABdhPJwNupJ7TLBkHQhV8Rj3sjwrcspC6FNuCR+MvPpgUkWKJA03eV5ppJQ7ihd5DZeoDGpDMbJVrw== X-Received: by 2002:a63:8f17:: with SMTP id n23mr53011860pgd.40.1594247364702; Wed, 08 Jul 2020 15:29:24 -0700 (PDT) Received: from [192.168.86.235] (c-73-241-150-58.hsd1.ca.comcast.net. [73.241.150.58]) by smtp.gmail.com with ESMTPSA id w9sm709825pfq.178.2020.07.08.15.29.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jul 2020 15:29:24 -0700 (PDT) Subject: Re: [PATCH net-next v2 2/2] net: sched: Lockless Token Bucket (LTB) qdisc To: "YU, Xiangning" , Linux Kernel Network Developers References: <4835f4cb-eee0-81e7-d935-5ad85767802c@alibaba-inc.com> From: Eric Dumazet Message-ID: <554197ce-cef1-0e75-06d7-56dbef7c13cc@gmail.com> Date: Wed, 8 Jul 2020 15:29:22 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <4835f4cb-eee0-81e7-d935-5ad85767802c@alibaba-inc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/8/20 9:38 AM, YU, Xiangning wrote: > Lockless Token Bucket (LTB) is a qdisc implementation that controls the > use of outbound bandwidth on a shared link. With the help of lockless > qdisc, and by decoupling rate limiting and bandwidth sharing, LTB is > designed to scale in the cloud data centers. > +static int ltb_enqueue(struct sk_buff *skb, struct Qdisc *sch, > + spinlock_t *root_lock, struct sk_buff **to_free) > +{ > + struct ltb_sched *ltb = qdisc_priv(sch); > + struct ltb_pcpu_sched *pcpu_q; > + struct ltb_pcpu_data *pcpu; > + struct ltb_class *cl; > + int cpu; > + > + pcpu = this_cpu_ptr(ltb->pcpu_data); > + pcpu_q = qdisc_priv(pcpu->qdisc); > + cpu = smp_processor_id(); > + ltb_skb_cb(skb)->cpu = cpu; > + > + cl = ltb_classify(sch, ltb, skb); > + if (unlikely(!cl)) { > + kfree_skb(skb); > + return NET_XMIT_DROP; > + } > + > + pcpu->active = true; > + if (unlikely(kfifo_put(&cl->aggr_queues[cpu], skb) == 0)) { > + kfree_skb(skb); > + atomic64_inc(&cl->stat_drops); qdisc drop counter should also be incremented. > + return NET_XMIT_DROP; > + } > + > + sch->q.qlen = 1; So, this is touching a shared cache line, why is it needed ? This looks some hack to me. > + pcpu_q->qdisc->q.qlen++; > + tasklet_schedule(&cl->aggr_tasklet); This is also touching a cache line. I really have doubts about scheduling a tasklet for every sent packet. (Particularly if majority of packets should not be rate limited)