aa5334b1f9
Joanne Koong says: ==================== Add a bhash2 table hashed by port + address This patchset proposes adding a bhash2 table that hashes by port and address. The motivation behind bhash2 is to expedite bind requests in situations where the port has many sockets in its bhash table entry, which makes checking bind conflicts costly especially given that we acquire the table entry spinlock while doing so, which can cause softirq cpu lockups and can prevent new tcp connections. We ran into this problem at Meta where the traffic team binds a large number of IPs to port 443 and the bind() call took a significant amount of time which led to cpu softirq lockups, which caused packet drops and other failures on the machine The patches are as follows: 1/2 - Adds a second bhash table (bhash2) hashed by port and address 2/2 - Adds a test for timing how long an additional bind request takes when the bhash entry is populated When experimentally testing this on a local server for ~24k sockets bound to the port, the results seen were: ipv4: before - 0.002317 seconds with bhash2 - 0.000018 seconds ipv6: before - 0.002431 seconds with bhash2 - 0.000021 seconds ==================== Link: https://lore.kernel.org/r/20220520001834.2247810-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text 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.