Cong Wang <xiyou.wangc...@gmail.com> writes:
> On Fri, May 4, 2018 at 12:10 PM, Toke Høiland-Jørgensen <t...@toke.dk> wrote:
>> Thank you for the review! A few comments below, I'll fix the rest.
>>
>>> [...]
>>>
>>> So sch_cake doesn't accept normal tc filters? Is this intentional?
>>> If so, why?
>>
>> For two reasons:
>>
>> - The two-level scheduling used in CAKE (tins / diffserv classes, and
>> flow hashing) does not map in an obvious way to the classification
>> index of tc filters.
>
> Sounds like you need to extend struct tcf_result?
Well, the obvious way to support filters would be to have skb->priority
override the diffserv mapping if set, and have the filter classification
result select the queue within that tier. That would probably be doable,
but see below.
>> - No one has asked for it. We have done our best to accommodate the
>> features people want in a home router qdisc directly in CAKE, and the
>> ability to integrate tc filters has never been requested.
>
> It is not hard to integrate, basically you need to call
> tcf_classify(). Although it is not mandatory, it is odd to merge a
> qdisc doesn't work with existing tc filters (and actions too).
I looked at the fq_codel code to do this. Is it possible to support
filtering without implementing Qdisc_class_ops? If so, I'll give it a
shot; but implementing the class ops is more than I can commit to...
>>>> +static int cake_init(struct Qdisc *sch, struct nlattr *opt,
>>>> + struct netlink_ext_ack *extack)
>>>> +{
>>>> + struct cake_sched_data *q = qdisc_priv(sch);
>>>> + int i, j;
>>>> +
>>>> + sch->limit = 10240;
>>>> + q->tin_mode = CAKE_DIFFSERV_BESTEFFORT;
>>>> + q->flow_mode = CAKE_FLOW_TRIPLE;
>>>> +
>>>> + q->rate_bps = 0; /* unlimited by default */
>>>> +
>>>> + q->interval = 100000; /* 100ms default */
>>>> + q->target = 5000; /* 5ms: codel RFC argues
>>>> + * for 5 to 10% of interval
>>>> + */
>>>> +
>>>> + q->cur_tin = 0;
>>>> + q->cur_flow = 0;
>>>> +
>>>> + if (opt) {
>>>> + int err = cake_change(sch, opt, extack);
>>>> +
>>>> + if (err)
>>>> + return err;
>>>
>>>
>>> Not sure if you really want to reallocate q->tines below for this
>>> case.
>>
>> I'm not sure what you mean here? If there's an error we return it and
>> the qdisc is not created. If there's not, we allocate and on subsequent
>> changes cake_change() will be called directly, or? Can the init function
>> ever be called again during the lifetime of the qdisc?
>>
>
> In non-error case, you call cake_change() first and then allocate
> ->tins with kvzalloc() below. For me it looks like you don't need to
> allocate it again when ->tins!=NULL.
No, we definitely don't. It's just not clear to me how cake_init() could
ever be called with q->tins already allocated?
I can add a check in any case, though, I see that there is one in
fq_codel as well...
-Toke
