Re: [RFC PATCH] mm: use precise current RSS for high-water accounting

[Nirmoy Das <nirmoyd@nvidia.com>]

Hi Mathieu,

On 2026-07-23 09:47, Mathieu Desnoyers wrote:
> Did you compare this with my hierarchical percpu counters series ?
>
> https://lore.kernel.org/lkml/20260707131544.75906-1-mathieu.desnoyers@efficios.com/
>
> I've sent it to Andrew two weeks ago but have not heard back from him
> though. My series attack the same issue you are trying to solve without
> increasing overhead when reading those counters.

I tested the v20 series on a dual-socket system with 352 CPUs and
64 KiB pages.

On the v7.2-rc4 test kernel without the series, getrusage03 failed
10/10:

  TFAIL: child.children = 270336, expected 307200

With v20, it also failed 10/10:

  TFAIL: initial.children = 0, expected 102400
  TFAIL: child.children = 262144, expected 307200

In v20, get_mm_hiwater_rss() still calls get_mm_rss(), which uses an
approximate counter read. The series did not help this test.

Let me know if you want to me to try out something else.

Thanks,
Nirmoy