Re: Unable to create htb tc classes more than 64K

[Akshat Kakkar <akshat.1984@gmail.com>]

Hi Eric,

Thanks for a detailed reply. Sorry I couldn't reply as I was
completely bed ridden.

In order for me to try this, I require few inputs (as I am new to all this)...

1. How do I register in Kernel, that my eBPF program should be called? Is this
https://netdevconf.info/1.1/proceedings/papers/On-getting-tc-classifier-fully-programmable-with-cls-bpf.pdf
and
http://man7.org/linux/man-pages/man8/tc-bpf.8.html
correct documents ?
2. Some info with respect to EDT and skb->tstamp and how things work.

On Mon, Aug 26, 2019 at 12:02 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 8/25/19 7:52 PM, Cong Wang wrote:
> > On Wed, Aug 21, 2019 at 11:00 PM Akshat Kakkar <akshat.1984@gmail.com> wrote:
> >>
> >> On Thu, Aug 22, 2019 at 3:37 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >>>> I am using ipset +  iptables to classify and not filters. Besides, if
> >>>> tc is allowing me to define qdisc -> classes -> qdsic -> classes
> >>>> (1,2,3 ...) sort of structure (ie like the one shown in ascii tree)
> >>>> then how can those lowest child classes be actually used or consumed?
> >>>
> >>> Just install tc filters on the lower level too.
> >>
> >> If I understand correctly, you are saying,
> >> instead of :
> >> tc filter add dev eno2 parent 100: protocol ip prio 1 handle
> >> 0x00000001 fw flowid 1:10
> >> tc filter add dev eno2 parent 100: protocol ip prio 1 handle
> >> 0x00000002 fw flowid 1:20
> >> tc filter add dev eno2 parent 100: protocol ip prio 1 handle
> >> 0x00000003 fw flowid 2:10
> >> tc filter add dev eno2 parent 100: protocol ip prio 1 handle
> >> 0x00000004 fw flowid 2:20
> >>
> >>
> >> I should do this: (i.e. changing parent to just immediate qdisc)
> >> tc filter add dev eno2 parent 1: protocol ip prio 1 handle 0x00000001
> >> fw flowid 1:10
> >> tc filter add dev eno2 parent 1: protocol ip prio 1 handle 0x00000002
> >> fw flowid 1:20
> >> tc filter add dev eno2 parent 2: protocol ip prio 1 handle 0x00000003
> >> fw flowid 2:10
> >> tc filter add dev eno2 parent 2: protocol ip prio 1 handle 0x00000004
> >> fw flowid 2:20
> >
> >
> > Yes, this is what I meant.
> >
> >
> >>
> >> I tried this previously. But there is not change in the result.
> >> Behaviour is exactly same, i.e. I am still getting 100Mbps and not
> >> 100kbps or 300kbps
> >>
> >> Besides, as I mentioned previously I am using ipset + skbprio and not
> >> filters stuff. Filters I used just to test.
> >>
> >> ipset  -N foo hash:ip,mark skbinfo
> >>
> >> ipset -A foo 10.10.10.10, 0x0x00000001 skbprio 1:10
> >> ipset -A foo 10.10.10.20, 0x0x00000002 skbprio 1:20
> >> ipset -A foo 10.10.10.30, 0x0x00000003 skbprio 2:10
> >> ipset -A foo 10.10.10.40, 0x0x00000004 skbprio 2:20
> >>
> >> iptables -A POSTROUTING -j SET --map-set foo dst,dst --map-prio
> >
> > Hmm..
> >
> > I am not familiar with ipset, but it seems to save the skbprio into
> > skb->priority, so it doesn't need TC filter to classify it again.
> >
> > I guess your packets might go to the direct queue of HTB, which
> > bypasses the token bucket. Can you dump the stats and check?
>
> With more than 64K 'classes' I suggest to use a single FQ qdisc [1], and
> an eBPF program using EDT model (Earliest Departure Time)
>
> The BPF program would perform the classification, then find a data structure
> based on the 'class', and then update/maintain class virtual times and skb->tstamp
>
> TBF = bpf_map_lookup_elem(&map, &classid);
>
> uint64_t now = bpf_ktime_get_ns();
> uint64_t time_to_send = max(TBF->time_to_send, now);
>
> time_to_send += (u64)qdisc_pkt_len(skb) * NSEC_PER_SEC / TBF->rate;
> if (time_to_send > TBF->max_horizon) {
>     return TC_ACT_SHOT;
> }
> TBF->time_to_send = time_to_send;
> skb->tstamp = max(time_to_send, skb->tstamp);
> if (time_to_send - now > TBF->ecn_horizon)
>     bpf_skb_ecn_set_ce(skb);
> return TC_ACT_OK;
>
> tools/testing/selftests/bpf/progs/test_tc_edt.c shows something similar.
>
>
> [1]  MQ + FQ if the device is multi-queues.
>
>    Note that this setup scales very well on SMP, since we no longer are forced
>  to use a single HTB hierarchy (protected by a single spinlock)
>