On Fri, Aug 21, 2026 at 11:53:57AM +0200, David Hildenbrand (Arm) wrote: > On 8/21/26 02:03, Andrew Morton wrote: > > On Wed, 19 Aug 2026 00:05:35 -0700 Jason Miu <[email protected]> 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? > > > > Why are we mixing python and sh?
Oh HELL no. Only C in the selftests please. And python is replete with 'getting it to run locally' issues. I have venv PTSD... > > > > > > > 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. > > There was recently a discussion around performance tests, and one thought was > to > not carry these in the kernel tree at all. > > Stresstests, not sure. > > So agreed, that this shouldn't be an ordinary selftests (nothing we would want > to run autoamtically), but I am also not 100% sure about having performance / > stress tests in the kernel tree. It's all stuff we have to maintain and drag > along. Agreed. Separate please. Stress tests are just asking for flakes :) they are useful + important but something different. > > > > > > > > > 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. > > There were recent discussions where I raised the same. I would prefer if > testing > kernel modules are somewhere in tools/testing/ if possible. Yes. > > > -- > Cheers, > > David -- Cheers, Lorenzo
