Messages in this thread Patch in this message | | | From | Jamal Hadi Salim <> | Date | Thu, 15 Feb 2024 12:49:05 -0500 | Subject | Re: [PATCH net-next 3/3] net: sched: make skip_sw actually skip software |
| |
On Thu, Feb 15, 2024 at 11:06 AM Asbjørn Sloth Tønnesen <ast@fiberby.net> wrote: > > TC filters come in 3 variants: > - no flag (no opinion, process wherever possible) > - skip_hw (do not process filter by hardware) > - skip_sw (do not process filter by software) > > However skip_sw is implemented so that the skip_sw > flag can first be checked, after it has been matched. > > IMHO it's common when using skip_sw, to use it on all rules. > > So if all filters in a block is skip_sw filters, then > we can bail early, we can thus avoid having to match > the filters, just to check for the skip_sw flag. > > +----------------------------+--------+--------+--------+ > | Test description | Pre | Post | Rel. | > | | kpps | kpps | chg. | > +----------------------------+--------+--------+--------+ > | basic forwarding + notrack | 1264.9 | 1277.7 | 1.01x | > | switch to eswitch mode | 1067.1 | 1071.0 | 1.00x | > | add ingress qdisc | 1056.0 | 1059.1 | 1.00x | > +----------------------------+--------+--------+--------+ > | 1 non-matching rule | 927.9 | 1057.1 | 1.14x | > | 10 non-matching rules | 495.8 | 1055.6 | 2.13x | > | 25 non-matching rules | 280.6 | 1053.5 | 3.75x | > | 50 non-matching rules | 162.0 | 1055.7 | 6.52x | > | 100 non-matching rules | 87.7 | 1019.0 | 11.62x | > +----------------------------+--------+--------+--------+ > > perf top (100 n-m skip_sw rules - pre patch): > 25.57% [kernel] [k] __skb_flow_dissect > 20.77% [kernel] [k] rhashtable_jhash2 > 14.26% [kernel] [k] fl_classify > 13.28% [kernel] [k] fl_mask_lookup > 6.38% [kernel] [k] memset_orig > 3.22% [kernel] [k] tcf_classify > > perf top (100 n-m skip_sw rules - post patch): > 4.28% [kernel] [k] __dev_queue_xmit > 3.80% [kernel] [k] check_preemption_disabled > 3.68% [kernel] [k] nft_do_chain > 3.08% [kernel] [k] __netif_receive_skb_core.constprop.0 > 2.59% [kernel] [k] mlx5e_xmit > 2.48% [kernel] [k] mlx5e_skb_from_cqe_mpwrq_nonlinear >
The concept makes sense - but i am wondering when you have a mix of skip_sw and skip_hw if it makes more sense to just avoid looking up skip_sw at all in the s/w datapath? Potentially by separating the hashes for skip_sw/hw. I know it's a deeper surgery - but would be more general purpose....unless i am missing something
> Test setup: > DUT: Intel Xeon D-1518 (2.20GHz) w/ Nvidia/Mellanox ConnectX-6 Dx 2x100G > Data rate measured on switch (Extreme X690), and DUT connected as > a router on a stick, with pktgen and pktsink as VLANs. > Pktgen was in range 12.79 - 12.95 Mpps across all tests. >
Hrm. Those are "tiny" numbers (25G @64B is about 3x that). What are the packet sizes? Perhaps the traffic generator is a limitation here? Also feels like you are doing exact matches? A sample flower rule would have helped.
cheers, jamal > Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net> > --- > include/net/pkt_cls.h | 5 +++++ > net/core/dev.c | 3 +++ > 2 files changed, 8 insertions(+) > > diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h > index a4ee43f493bb..a065da4df7ff 100644 > --- a/include/net/pkt_cls.h > +++ b/include/net/pkt_cls.h > @@ -74,6 +74,11 @@ static inline bool tcf_block_non_null_shared(struct tcf_block *block) > return block && block->index; > } > > +static inline bool tcf_block_has_skip_sw_only(struct tcf_block *block) > +{ > + return block && atomic_read(&block->filtercnt) == atomic_read(&block->skipswcnt); > +} > + > static inline struct Qdisc *tcf_block_q(struct tcf_block *block) > { > WARN_ON(tcf_block_shared(block)); > diff --git a/net/core/dev.c b/net/core/dev.c > index d8dd293a7a27..7cd014e5066e 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -3910,6 +3910,9 @@ static int tc_run(struct tcx_entry *entry, struct sk_buff *skb, > if (!miniq) > return ret; > > + if (tcf_block_has_skip_sw_only(miniq->block)) > + return ret; > + > tc_skb_cb(skb)->mru = 0; > tc_skb_cb(skb)->post_ct = false; > tcf_set_drop_reason(skb, *drop_reason); > -- > 2.43.0 >
| |