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Patch series "Add a command line option that enables control of how many threads should be used to allocate huge pages", v2. Allocating huge pages can take a very long time on servers with terabytes of memory even when they are allocated at boot time where the allocation happens in parallel. Before this series, the kernel used a hard coded value of 2 threads per NUMA node for these allocations. This value might have been good enough in the past but it is not sufficient to fully utilize newer systems. This series changes the default so the kernel uses 25% of the available hardware threads for these allocations. In addition, we allow the user that wish to micro-optimize the allocation time to override this value via a new kernel parameter. We tested this on 2 generations of Xeon CPUs and the results show a big improvement of the overall allocation time. +-----------------------+-------+-------+-------+-------+-------+ | threads | 8 | 16 | 32 | 64 | 128 | +-----------------------+-------+-------+-------+-------+-------+ | skylake 144 cpus | 44s | 22s | 16s | 19s | 20s | | cascade lake 192 cpus | 39s | 20s | 11s | 10s | 9s | +-----------------------+-------+-------+-------+-------+-------+ On skylake, we see an improvment of 2.75x when using 32 threads, on cascade lake we can get even better at 4.3x when we use 128 threads. This speedup is quite significant and users of large machines like these should have the option to make the machines boot as fast as possible. This patch (of 3): Before this patch, the kernel currently used a hard coded value of 2 threads per NUMA node for these allocations. This patch changes this policy and the kernel now uses 25% of the available hardware threads for the allocations. Link: https://lkml.kernel.org/r/20250227-hugepage-parameter-v2-0-7db8c6dc0453@cyberus-technology.de Link: https://lkml.kernel.org/r/20250227-hugepage-parameter-v2-1-7db8c6dc0453@cyberus-technology.de Signed-off-by: Thomas Prescher <thomas.prescher@cyberus-technology.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.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.