linux-kernel - [PATCH net-next v4 0/3] make skip

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Date: Mon, 25 Mar 2024 20:47:33 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Jiri Pirko <jiri@...nulli.us>
Cc: Asbjørn Sloth Tønnesen <ast@...erby.net>,
	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Vlad Buslov <vladbu@...dia.com>,
	Marcelo Ricardo Leitner <mleitner@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	llu@...erby.dk
Subject: [PATCH net-next v4 0/3] make skip_sw actually skip software

Hi,

During development of flower-route[1], which I
recently presented at FOSDEM[2], I noticed that
CPU usage, would increase the more rules I installed
into the hardware for IP forwarding offloading.

Since we use TC flower offload for the hottest
prefixes, and leave the long tail to the normal (non-TC)
Linux network stack for slow-path IP forwarding.
We therefore need both the hardware and software
datapath to perform well.

I found that skip_sw rules, are quite expensive
in the kernel datapath, since they must be evaluated
and matched upon, before the kernel checks the
skip_sw flag.

This patchset optimizes the case where all rules
are skip_sw, by implementing a TC bypass for these
cases, where TC is only used as a control plane
for the hardware path.

v4:
- Rebased onto net-next, now that net-next is open again

v3: https://lore.kernel.org/netdev/20240306165813.656931-1-ast@fiberby.net/
- Patch 3:
  - Fix source_inline
  - Fix build failure, when CONFIG_NET_CLS without CONFIG_NET_CLS_ACT.

v2: https://lore.kernel.org/netdev/20240305144404.569632-1-ast@fiberby.net/
- Patch 1:
  - Add Reviewed-By from Jiri Pirko
- Patch 2:
  - Move code, to avoid forward declaration (Jiri).
- Patch 3
  - Refactor to use a static key.
  - Add performance data for trapping, or sending
    a packet to a non-existent chain (as suggested by Marcelo).

v1: https://lore.kernel.org/netdev/20240215160458.1727237-1-ast@fiberby.net/

[1] flower-route
    https://github.com/fiberby-dk/flower-route

[2] FOSDEM talk
    https://fosdem.org/2024/schedule/event/fosdem-2024-3337-flying-higher-hardware-offloading-with-bird/

Asbjørn Sloth Tønnesen (3):
  net: sched: cls_api: add skip_sw counter
  net: sched: cls_api: add filter counter
  net: sched: make skip_sw actually skip software

 include/net/pkt_cls.h     |  9 +++++++++
 include/net/sch_generic.h |  4 ++++
 net/core/dev.c            | 10 ++++++++++
 net/sched/cls_api.c       | 41 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 64 insertions(+)

-- 
2.43.0