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Adding an unlikely() hint on the n < 0 comparison return path improves run-time performance of the select() system call, the negative value of n is very uncommon in normal select usage. Benchmarking on an Debian based Intel(R) Core(TM) Ultra 9 285K with a 6.15-rc1 kernel built with 14.2.0 using a select of 1000 file descriptors with zero timeout shows a consistent call reduction from 258 ns down to 254 ns, which is a ~1.5% performance improvement. Results based on running 25 tests with turbo disabled (to reduce clock freq turbo changes), with 30 second run per test and comparing the number of select() calls per second. The % standard deviation of the 25 tests was 0.24%, so results are reliable. Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Link: https://lore.kernel.org/20250414092426.53529-1-colin.i.king@gmail.com Signed-off-by: Christian Brauner <brauner@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
``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.