Re: [PATCH net-next 0/4] net-sysfs: remove the rtnl_trylock/restart_syscall construction

Hi Antoine,

On Fri, 17 Jan 2025 11:26:07 +0100
Antoine Tenart [off-list ref] wrote:

Hi,

The series initially aimed at improving spins (and thus delays) while
accessing net sysfs under rtnl lock contention[1]. The culprit was the
trylock/restart_syscall constructions. There wasn't much interest at the
time but it got traction recently for other reasons (lowering the rtnl
lock pressure).

Since the RFC[1]:

- Limit the breaking of the sysfs protection to sysfs_rtnl_lock() only
  as this is not needed in the whole rtnl locking section thanks to the
  additional check on dev_isalive(). This simplifies error handling as
  well as the unlocking path.
- Used an interruptible version of rtnl_lock, as done by Jakub in
  his experiments.
- Removed a WARN_ONCE_ONCE call [Greg].
- Removed explicit inline markers [Stephen].

Most of the reasoning is explained in comments added in patch 1. This
was tested by stress-testing net sysfs attributes (read/write ops) while
adding/removing queues and adding/removing veths, all in parallel. I
also used an OCP single node cluster, spawning lots of pods.

Thanks,
Antoine

[1] https://lore.kernel.org/all/20231018154804.420823-1-atenart@kernel.org/T/ (local)

Thanks for that work, it looks like this would address this problem
faced recently by Christophe (in CC) :

https://lore.kernel.org/netdev/d416a14ec38c7ba463341b83a7a9ec6ccc435246.1734419614.git.christophe.leroy@csgroup.eu/ (local)

Thanks,

Maxime