047f340b36
TC filters come in 3 variants: - no flag (try to process in hardware, but fallback to software)) - 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. This patch adds a bypass, for when only TC skip_sw rules are used. The bypass is guarded by a static key, to avoid harming other workloads. There are 3 ways that a packet from a skip_sw ruleset, can end up in the kernel path. Although the send packets to a non-existent chain way is only improved a few percents, then I believe it's worth optimizing the trap and fall-though use-cases. +----------------------------+--------+--------+--------+ | Test description | Pre- | Post- | Rel. | | | kpps | kpps | chg. | +----------------------------+--------+--------+--------+ | basic forwarding + notrack | 3589.3 | 3587.9 | 1.00x | | switch to eswitch mode | 3081.8 | 3094.7 | 1.00x | | add ingress qdisc | 3042.9 | 3063.6 | 1.01x | | tc forward in hw / skip_sw |37024.7 |37028.4 | 1.00x | | tc forward in sw / skip_hw | 3245.0 | 3245.3 | 1.00x | +----------------------------+--------+--------+--------+ | tests with only skip_sw rules below: | +----------------------------+--------+--------+--------+ | 1 non-matching rule | 2694.7 | 3058.7 | 1.14x | | 1 n-m rule, match trap | 2611.2 | 3323.1 | 1.27x | | 1 n-m rule, goto non-chain | 2886.8 | 2945.9 | 1.02x | | 5 non-matching rules | 1958.2 | 3061.3 | 1.56x | | 5 n-m rules, match trap | 1911.9 | 3327.0 | 1.74x | | 5 n-m rules, goto non-chain| 2883.1 | 2947.5 | 1.02x | | 10 non-matching rules | 1466.3 | 3062.8 | 2.09x | | 10 n-m rules, match trap | 1444.3 | 3317.9 | 2.30x | | 10 n-m rules,goto non-chain| 2883.1 | 2939.5 | 1.02x | | 25 non-matching rules | 838.5 | 3058.9 | 3.65x | | 25 n-m rules, match trap | 824.5 | 3323.0 | 4.03x | | 25 n-m rules,goto non-chain| 2875.8 | 2944.7 | 1.02x | | 50 non-matching rules | 488.1 | 3054.7 | 6.26x | | 50 n-m rules, match trap | 484.9 | 3318.5 | 6.84x | | 50 n-m rules,goto non-chain| 2884.1 | 2939.7 | 1.02x | +----------------------------+--------+--------+--------+ perf top (25 n-m skip_sw rules - pre patch): 20.39% [kernel] [k] __skb_flow_dissect 16.43% [kernel] [k] rhashtable_jhash2 10.58% [kernel] [k] fl_classify 10.23% [kernel] [k] fl_mask_lookup 4.79% [kernel] [k] memset_orig 2.58% [kernel] [k] tcf_classify 1.47% [kernel] [k] __x86_indirect_thunk_rax 1.42% [kernel] [k] __dev_queue_xmit 1.36% [kernel] [k] nft_do_chain 1.21% [kernel] [k] __rcu_read_lock perf top (25 n-m skip_sw rules - post patch): 5.12% [kernel] [k] __dev_queue_xmit 4.77% [kernel] [k] nft_do_chain 3.65% [kernel] [k] dev_gro_receive 3.41% [kernel] [k] check_preemption_disabled 3.14% [kernel] [k] mlx5e_skb_from_cqe_mpwrq_nonlinear 2.88% [kernel] [k] __netif_receive_skb_core.constprop.0 2.49% [kernel] [k] mlx5e_xmit 2.15% [kernel] [k] ip_forward 1.95% [kernel] [k] mlx5e_tc_restore_tunnel 1.92% [kernel] [k] vlan_gro_receive 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-dpdk was in range 36.6-37.7 Mpps 64B packets across all tests. Full test data at https://files.fiberby.net/ast/2024/tc_skip_sw/v2_tests/ Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net> Reviewed-by: Simon Horman <horms@kernel.org> Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.