Re: [RFC PATCH 0/3] selftests: mm: introduce page allocation stall reproducer

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 19 Aug 2026 00:05:35 -0700 Jason Miu <jasonmiu@google.com> wrote:

> Background
> ==========
> Under severe system memory pressure, system unresponsiveness often 
> occurs due to page allocation stalls. In commit 94e0bcde055e ("mm, 
> page_alloc: reintroduce page allocation stall warning"), David Rientjes 
> introduced a warning mechanism to emit a kernel log when a page 
> allocation takes longer than 10 seconds. This log is used to correlate
> a frozen system with the system memory state at the time of failure.
> 
> To further debug and analyze these allocation stalls, we need a 
> reproducible test case. This patch series introduces a new selftest 
> designed to artificially mimic the severe memory pressure scenarios 
> seen in production, allowing us to observe the resulting allocation 
> stalls.

Interesting.

>  lib/Kconfig.debug                             |  11 +
>  lib/Makefile                                  |   1 +
>  lib/test_mempress_timer.c                     | 140 +++++++++++
>  .../testing/selftests/mm/page_alloc_stall.sh  |  80 ++++++
>  .../selftests/mm/page_alloc_stall_pressure.py | 235 ++++++++++++++++++
>  5 files changed, 467 insertions(+)
>  create mode 100644 lib/test_mempress_timer.c
>  create mode 100644 tools/testing/selftests/mm/page_alloc_stall.sh
>  create mode 100644 tools/testing/selftests/mm/page_alloc_stall_pressure.py

Nothing fits very well, does it?



selftests is for quick tests which are run by run_kselftest.sh.  You
had to place it in selftests because there isn't anywhere obvious for
it to live.

So I suggest a brand new tools/testing/stresstests/mm.  If we create
this, people will jump on it and start adding things which presently
reside in their personal collections.



I can't say I like "mempress".  Is "memory_pressure" too wordy?



All of lib/test*.c shouldn't be in lib/.  lib/ is for library code! 
Again, we put them there because people are shy about doing mkdir.


Sashiko said hello:
	https://sashiko.dev/#/patchset/20260819070538.2404983-1-jasonmiu@google.com


In [patch 1/3], s/__GFP_NOFAIL// and s/cond_resched()//.