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Reading mm::mm_users and mm:::mm_cid::nr_cpus_allowed every time to compute the maximal CID value is just wasteful as that value is only changing on fork(), exit() and eventually when the affinity changes. So it can be easily precomputed at those points and provided in mm::mm_cid for consumption in the hot path. But there is an issue with using mm::mm_users for accounting because that does not necessarily reflect the number of user space tasks as other kernel code can take temporary references on the MM which skew the picture. Solve that by adding a users counter to struct mm_mm_cid, which is modified by fork() and exit() and used for precomputing under mm_mm_cid::lock. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://patch.msgid.link/20251119172549.832764634@linutronix.de
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.