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
