linux-kernel - [PATCH net-next v3 0/4] netconsole: Optimize console registration and improve testing

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Message-Id: <20250609-netcons_ext-v3-0-5336fa670326@debian.org>
Date: Mon, 09 Jun 2025 02:46:25 -0700
From: Breno Leitao <leitao@...ian.org>
To: Breno Leitao <leitao@...ian.org>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Tejun Heo <tj@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
 Shuah Khan <shuah@...nel.org>, horms@...nel.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 gustavold@...il.com, Usama Arif <usamaarif642@...il.com>, 
 linux-kselftest@...r.kernel.org, kernel-team@...a.com
Subject: [PATCH net-next v3 0/4] netconsole: Optimize console registration
 and improve testing

During performance analysis of console subsystem latency, I discovered that
netconsole registers console handlers even when no active targets exist.
These orphaned console handlers are invoked on every printk() call, get
the lock, iterate through empty target lists, and consume CPU cycles
without performing any useful work.

This patch series addresses the inefficiency by:

1. Implementing dynamic console registration/unregistration based on target
   availability, ensuring console handlers are only active when needed
2. Adding automatic cleanup of unused console registrations when targets
   are disabled or removed
3. Extending the selftest suite to cover non-extended console format,
   which was previously untested

The optimization reduces printk() overhead by eliminating unnecessary
function calls and list traversals when netconsole targets are not
configured, improving overall system performance during heavy logging
scenarios.

---
Changes in v3:
- Set CON_ENABLED before re-enabling the console, to fix a selftest that
  was failing, as reported by Jakub on v2.
- Link to v2: https://lore.kernel.org/r/20250602-netcons_ext-v2-0-ef88d999326d@debian.org

Changes in v2:
- Added selftests to test the new mechanism
- Unregister the console if the last target got disabled
- Sending to net-next instead of net (Jakub)
- Link to v1: https://lore.kernel.org/r/20250528-netcons_ext-v1-1-69f71e404e00@debian.org

---
Breno Leitao (4):
      netconsole: Only register console drivers when targets are configured
      netconsole: Add automatic console unregistration on target removal
      selftests: netconsole: Do not exit from inside the validation function
      selftests: netconsole: Add support for basic netconsole target format

 drivers/net/netconsole.c                           | 67 +++++++++++++++++++---
 .../selftests/drivers/net/lib/sh/lib_netcons.sh    | 27 +++++++--
 .../testing/selftests/drivers/net/netcons_basic.sh | 50 ++++++++++------
 3 files changed, 112 insertions(+), 32 deletions(-)
---
base-commit: 2c7e4a2663a1ab5a740c59c31991579b6b865a26
change-id: 20250528-netcons_ext-572982619bea

Best regards,
-- 
Breno Leitao <leitao@...ian.org>