Re: [PATCH 6/6] net: move qdisc ingress filtering on top of netfilter ingress hooks

Daniel Borkmann
2015-04-30T23:01:14Z

On 04/30/2015 09:16 PM, Daniel Borkmann wrote:
> On 04/30/2015 06:36 PM, Pablo Neira Ayuso wrote:
> ...
>> But where are the barriers? These unfounded performance claims are
>> simply absurd, qdisc ingress barely performs a bit better just because
>> it executes a bit less code and only in the single CPU scenario with
>> no rules at all.
>
> I think we're going in circles a bit. :( You are right in saying that
> currently, there's a central spinlock, which is worked on to get rid
> of, you've seen the patch on the list floating around already. Single
> CPU, artificial micro-benchmark, which were done show that you see on
> your machine ~613Kpps to ~545Kpps, others have seen it more amplified
> as 22.4Mpps to 18.0Mpps drop from __netif_receive_skb_core() up to an
> empty dummy u32_classify() rule, which has already been acknowledged
> that this gap needs to be improved. Lets call it unfounded then. I
> think we wouldn't even have this discussion if we wouldn't try brute
> forcing both worlds behind this single static key, or, have both
> invoked from within the same layer/list.

Ok, out of curiosity, I did the same as both of you: I'm using a pretty
standard Supermicro X10SLM-F/X10SLM-F, Xeon E3-1240 v3.

*** ingress + dummy u32, net-next:

w/o perf:
...
Result: OK: 5157948(c5157388+d559) usec, 100000000 (60byte,0frags)
19387551pps 9306Mb/sec (9306024480bps) errors: 100000000

perf record -C0 -ecycles:k ./pktgen.sh p1p1
...
Result: OK: 5182638(c5182057+d580) usec, 100000000 (60byte,0frags)
19295191pps 9261Mb/sec (9261691680bps) errors: 100000000

26.07% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb_core
14.39% kpktgend_0 [kernel.kallsyms] [k] kfree_skb
13.69% kpktgend_0 [cls_u32] [k] u32_classify
11.75% kpktgend_0 [kernel.kallsyms] [k] _raw_spin_lock
5.34% kpktgend_0 [sch_ingress] [k] ingress_enqueue
5.21% kpktgend_0 [kernel.kallsyms] [k] tc_classify_compat
4.93% kpktgend_0 [kernel.kallsyms] [k] skb_defer_rx_timestamp
3.41% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_internal
3.21% kpktgend_0 [pktgen] [k] pktgen_thread_worker
3.16% kpktgend_0 [kernel.kallsyms] [k] tc_classify
3.08% kpktgend_0 [kernel.kallsyms] [k] ip_rcv
2.05% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb
1.60% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_sk
1.15% kpktgend_0 [kernel.kallsyms] [k] classify
0.45% kpktgend_0 [kernel.kallsyms] [k] __local_bh_enable_ip

*** nf hook infra + ingress + dummy u32, net-next:

w/o perf:
...
Result: OK: 6555903(c6555744+d159) usec, 100000000 (60byte,0frags)
15253426pps 7321Mb/sec (7321644480bps) errors: 100000000

perf record -C0 -ecycles:k ./pktgen.sh p1p1
...
Result: OK: 6591291(c6591153+d138) usec, 100000000 (60byte,0frags)
15171532pps 7282Mb/sec (7282335360bps) errors: 100000000

25.94% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb_core
12.19% kpktgend_0 [kernel.kallsyms] [k] kfree_skb
11.00% kpktgend_0 [kernel.kallsyms] [k] _raw_spin_lock
10.58% kpktgend_0 [cls_u32] [k] u32_classify
5.34% kpktgend_0 [sch_ingress] [k] handle_ing
4.68% kpktgend_0 [kernel.kallsyms] [k] nf_iterate
4.33% kpktgend_0 [kernel.kallsyms] [k] tc_classify_compat
4.32% kpktgend_0 [sch_ingress] [k] ingress_enqueue
3.62% kpktgend_0 [kernel.kallsyms] [k] skb_defer_rx_timestamp
2.95% kpktgend_0 [kernel.kallsyms] [k] nf_hook_slow
2.75% kpktgend_0 [kernel.kallsyms] [k] ip_rcv
2.60% kpktgend_0 [kernel.kallsyms] [k] tc_classify
2.52% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_internal
2.50% kpktgend_0 [pktgen] [k] pktgen_thread_worker
1.77% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb
1.28% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_sk
0.94% kpktgend_0 [kernel.kallsyms] [k] classify
0.38% kpktgend_0 [kernel.kallsyms] [k] __local_bh_enable_ip

*** drop ingress spinlock (patch w/ bstats addition) + ingress +
dummy u32, net-next:

w/o perf:
...
Result: OK: 4789828(c4789353+d474) usec, 100000000 (60byte,0frags)
20877576pps 10021Mb/sec (10021236480bps) errors: 100000000

perf record -C0 -ecycles:k ./pktgen.sh p1p1
...
Result: OK: 4829276(c4828437+d839) usec, 100000000 (60byte,0frags)
20707036pps 9939Mb/sec (9939377280bps) errors: 100000000

33.11% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb_core
15.27% kpktgend_0 [kernel.kallsyms] [k] kfree_skb
14.60% kpktgend_0 [cls_u32] [k] u32_classify
6.06% kpktgend_0 [sch_ingress] [k] ingress_enqueue
5.55% kpktgend_0 [kernel.kallsyms] [k] tc_classify_compat
5.31% kpktgend_0 [kernel.kallsyms] [k] skb_defer_rx_timestamp
3.77% kpktgend_0 [pktgen] [k] pktgen_thread_worker
3.45% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_internal
3.33% kpktgend_0 [kernel.kallsyms] [k] tc_classify
3.33% kpktgend_0 [kernel.kallsyms] [k] ip_rcv
2.34% kpktgend_0 [kernel.kallsyms] [k] __netif_receive_skb
1.78% kpktgend_0 [kernel.kallsyms] [k] netif_receive_skb_sk
1.15% kpktgend_0 [kernel.kallsyms] [k] classify
0.48% kpktgend_0 [kernel.kallsyms] [k] __local_bh_enable_ip

That means, here, moving ingress behind nf hooks, I see a similar
slowdown in this micro-benchmark as Alexei of really worst case
of ~27%.

Now in real world that might probably just end up as a few percent
depending on the use case, but really, why should we go down that
path if we can just avoid that?

If you find a way, where both tc/nf hooks are triggered from within
the same list, then that would probably look better already. Or,
as a start, as mentioned, with a second static key for netfilter,
which can later on then still be reworked for a better integration,
although I agree with you that it's less clean and I see the point
of consolidating code.

If you want, I'm happy to provide numbers if you have a next set as
well, feel free to ping me.

Thanks,
Daniel