netdev - Re: [PATCH net-next] net:sched: add gkprio scheduler

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Message-ID: <CAM_iQpW7eGBffVMtBt1b1SHpLL5fbD1doRpUcVXW2U-rw4rOiQ@mail.gmail.com>
Date:   Tue, 8 May 2018 19:24:35 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Michel Machado <michel@...irati.com.br>
Cc:     Nishanth Devarajan <ndev2021@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cody Doucette <doucette@...edu>
Subject: Re: [PATCH net-next] net:sched: add gkprio scheduler

On Tue, May 8, 2018 at 5:59 AM, Michel Machado <michel@...irati.com.br> wrote:
>>> Overall it looks good to me, just one thing below:
>>>
>>>> +struct Qdisc_ops gkprio_qdisc_ops __read_mostly = {
>>>> +       .id             =       "gkprio",
>>>> +       .priv_size      =       sizeof(struct gkprio_sched_data),
>>>> +       .enqueue        =       gkprio_enqueue,
>>>> +       .dequeue        =       gkprio_dequeue,
>>>> +       .peek           =       qdisc_peek_dequeued,
>>>> +       .init           =       gkprio_init,
>>>> +       .reset          =       gkprio_reset,
>>>> +       .change         =       gkprio_change,
>>>> +       .dump           =       gkprio_dump,
>>>> +       .destroy        =       gkprio_destroy,
>>>> +       .owner          =       THIS_MODULE,
>>>> +};
>>>
>>>
>>> You probably want to add Qdisc_class_ops here so that you can
>>> dump the stats of each internal queue.
>
>
> Hi Cong,
>
>    In the production scenario we are targeting, this priority queue must be
> classless; being classful would only bloat the code for us. I don't see
> making this queue classful as a problem per se, but I suggest leaving it as
> a future improvement for when someone can come up with a useful scenario for
> it.


Take a look at sch_prio, it is fairly simple since your internal
queues are just an array... Per-queue stats are quite useful
in production, we definitely want to observe which queues are
full which are not.