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When testing perf trace on NixOS, I noticed significant startup delays: - `ls`: ~2ms - `strace ls`: ~10ms - `perf trace ls`: ~550ms Profiling showed that 51% of the time is spent reading files, 26% in loading BPF programs, and 11% in `newfstatat`. This patch optimizes module path exploration by avoiding `stat()` calls unless necessary. For filesystems that do not implement `d_type` (DT_UNKNOWN), it falls back to the old behavior. See `readdir(3)` for details. This reduces `perf trace ls` time to ~500ms. A more thorough startup optimization based on command parameters would be ideal, but that is a larger effort. Signed-off-by: Krzysztof Łopatowski <krzysztof.m.lopatowski@gmail.com> Acked-by: Howard Chu <howardchu95@gmail.com> Link: https://lore.kernel.org/r/20250206113314.335376-2-krzysztof.m.lopatowski@gmail.com Signed-off-by: Namhyung Kim <namhyung@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.