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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id l15sm433868pjq.1.2020.07.08.14.37.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jul 2020 14:37:03 -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 14:37:01 -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. > ... This ltb_class struct has a size of 1579584 bytes :/ > +struct ltb_class { > + struct Qdisc_class_common common; > + struct psched_ratecfg ratecfg; > + struct psched_ratecfg ceilcfg; > + u32 prio; > + struct ltb_class *parent; > + struct Qdisc *qdisc; > + struct Qdisc *root_qdisc; > + u32 classid; > + struct list_head pnode; > + unsigned long state; ____cacheline_aligned_in_smp > + > + /* Aggr/drain context only */ > + s64 next_timestamp; ____cacheline_aligned_in_smp > + int num_cpus; > + int last_cpu; > + s64 bw_used; > + s64 last_bytes; > + s64 last_timestamp; > + s64 stat_bytes; > + s64 stat_packets; > + atomic64_t stat_drops; > + > + /* Balance delayed work only */ > + s64 rate; ____cacheline_aligned_in_smp > + s64 ceil; > + s64 high_water; > + int drop_delay; > + s64 bw_allocated; > + bool want_more; > + > + /* Shared b/w aggr/drain thread and balancer */ > + unsigned long curr_interval; ____cacheline_aligned_in_smp > + s64 bw_measured; /* Measured actual bandwidth */ > + s64 maxbw; /* Calculated bandwidth */ > + > + STRUCT_KFIFO(struct sk_buff *, SKB_QLEN) aggr_queues[MAX_CPU_COUNT]; > + ____cacheline_aligned_in_smp > + STRUCT_KFIFO(struct sk_buff *, SKB_QLEN * MAX_CPU_COUNT) drain_queue; > + ____cacheline_aligned_in_smp > + STRUCT_KFIFO(struct sk_buff *, SKB_QLEN) fanout_queues[MAX_CPU_COUNT]; > + ____cacheline_aligned_in_smp > + > + struct tasklet_struct aggr_tasklet; > + struct hrtimer aggr_timer; > +}; > + > > + > +static struct ltb_class *ltb_alloc_class(struct Qdisc *sch, > + struct ltb_class *parent, u32 classid, > + struct psched_ratecfg *ratecfg, > + struct psched_ratecfg *ceilcfg, > + u32 prio) > +{ > + struct ltb_sched *ltb = qdisc_priv(sch); > + struct ltb_class *cl; > + int i; > + > + if (ratecfg->rate_bytes_ps > ceilcfg->rate_bytes_ps || > + prio < 0 || prio >= TC_LTB_NUMPRIO) > + return NULL; > + > + cl = kzalloc(sizeof(*cl), GFP_KERNEL); This is going to fail, 2MB chunks of physically contiguous memory is unreasonable. 2MB per class makes this qdisc very particular, especially with 1000 classes ? In comparison, HTB class consumes less than 1 KB