Re: [PATCH v2] fork: stop ignoring NUMA while handling cached thread stacks

[Linus Walleij]

On Thu, Nov 20, 2025 at 6:40 AM Mateusz Guzik <mjguzik@xxxxxxxxx> wrote:

> 1. the numa parameter was straight up ignored.
> 2. nothing was done to check if the to-be-cached/allocated stack matches
>    the local node
>
> The id remains ignored on free in case of memoryless nodes.
>
> Note the current caching is already bad as the cache keeps overflowing
> and a different solution is needed for the long run, to be worked
> out(tm).
>
> Stats collected over a kernel build with the patch with the following
> topology:
>   NUMA node(s):              2
>   NUMA node0 CPU(s):         0-11
>   NUMA node1 CPU(s):         12-23
>
> caller's node vs stack backing pages on free:
> matching:       50083 (70%)
> mismatched:     21492 (30%)
>
> caching efficiency:
> cached:         32651 (65.2%)
> dropped:        17432 (34.8%)
>
> Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx>

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij