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Kuniyuki Iwashima says: ==================== rtnetlink: Per-netns RTNL. rtnl_lock() is a "Big Kernel Lock" in the networking slow path and serialised all rtnetlink requests until 4.13. Since RTNL_FLAG_DOIT_UNLOCKED and RTNL_FLAG_DUMP_UNLOCKED have been introduced in 4.14 and 6.9, respectively, rtnetlink message handlers are ready to be converted to RTNL-less/free. 15 out of 44 dumpit()s have been converted to RCU so far, and the progress is pretty good. We can now dump various major network resources without RTNL. 12 out of 87 doit()s have been converted, but most of the converted doit()s are also on the reader side of RTNL; their message types are RTM_GET*. So, most of RTM_(NEW|DEL|SET)* operations are still serialised by RTNL. For example, one of our services creates 2K netns and a small number of network interfaces in each netns that require too many writer-side rtnetlink requests, and setting up a single host takes 10+ minutes. RTNL is still a huge pain for network configuration paths, and we need more granular locking, given converting all doit()s would be unfeasible. Actually, most RTNL users do not need to freeze multiple netns, and such users can be protected by per-netns RTNL mutex. The exceptions would be RTM_NEWLINK, RTM_DELLINK, and RTM_SETLINK. (See [0] and [1]) This series is the first step of the per-netns RTNL conversion that gradually replaces rtnl_lock() with rtnl_net_lock(net) under CONFIG_DEBUG_NET_SMALL_RTNL. [0]: https://netdev.bots.linux.dev/netconf/2024/index.html [1]: https://lpc.events/event/18/contributions/1959/ ==================== Link: https://patch.msgid.link/20241004221031.77743-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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.