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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id d65sm672079pfc.97.2020.07.08.15.08.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jul 2020 15:08:25 -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: Date: Wed, 8 Jul 2020 15:08:23 -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; > + } > Silently dropping a packet in a qdisc is forbidden. Instead we always make sure to increment a counter, so that "tc -s qdisc" can give a clue. qdisc_drop() is how we handle this. Then, you might hit an issue if 5,000,000 packets per second need to be dropped. (So you will probably need per cpu counters)