Re: [PATCH v9 1/2] lib: Introduce hierarchical per-cpu counters

[Andrew Morton]

On Sat, 22 Nov 2025 12:15:02 -0500 Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote:

> > 
> >>   include/linux/percpu_counter_tree.h | 239 +++++++++++++++
> >>   init/main.c                         |   2 +
> >>   lib/Makefile                        |   1 +
> >>   lib/percpu_counter_tree.c           | 443 ++++++++++++++++++++++++++++
> >>   4 files changed, 685 insertions(+)
> >>   create mode 100644 include/linux/percpu_counter_tree.h
> >>   create mode 100644 lib/percpu_counter_tree.c
> > 
> > An in-kernel test suite would be great.  Like lib/*test*.c or
> > tools/testing/.
> 
> I'll keep a note to port the tests from my userspace librseq
> percpu counters feature branch to the kernel. I did not do it
> initially because I wanted to see if the overall approach was
> deemed interesting for the kernel.

It deems interesting to me - certainly seems useful in addressing some
nasty problems.

If it hasn't been massacred by reviewers, please poke me in a week or
so and I'll look at giving it some exposure in mm.git's mm-new branch
(which isn't included in linux-next).