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Wed, 30 Sep 2026 08:04:07 -0700 (PDT) Received: from localhost.localdomain ([2001:af0:8000:1409:193:86:92:181]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a01e64dabfsm6953955e9.6.2026.09.30.08.04.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 08:04:07 -0700 (PDT) Date: Wed, 30 Sep 2026 17:04:05 +0200 To: Sebastian Chlad Message-ID: References: <20260926204459.20699-1-sebastianchlad@gmail.com> <20260926204459.20699-2-sebastianchlad@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20260926204459.20699-2-sebastianchlad@gmail.com> X-Virus-Scanned: clamav-milter 1.0.9 at in-7.smtp.seeweb.it X-Virus-Status: Clean Subject: Re: [LTP] [PATCH 1/2] memcg/memcontrol0[34]: Use expected values from the protection model X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: =?utf-8?q?Michal_Koutn=C3=BD_via_ltp?= Reply-To: Michal =?utf-8?Q?Koutn=C3=BD?= Cc: Sebastian Chlad , ltp@lists.linux.it Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" Hello. = On Sat, Sep 26, 2026 at 10:44:53PM +0200, Sebastian Chlad wrote: > From: Sebastian Chlad > = > memcontrol03 (memory.min) and memcontrol04 (memory.low) still expect > A/B/C ~=3D 33M and A/B/D ~=3D 17M after reclaim, which are the values from > the original kselftest. These were never derived from how the kernel > distributes protection among siblings, and the kselftest replaced them > with simulated values for both tests in kernel commit f10b6e9a8e66 > ("selftests: memcg: adjust expected reclaim values of protected > cgroups"): > = > A/B/C memory.current ~=3D 29M > A/B/D memory.current ~=3D 21M > = > (see tools/testing/selftests/cgroup/memcg_protection.m for the model). > = > Real kernels match the model, Note: this was true at the time of the model introduction but the contemporary kernels may diverge slightly from it. (Not conceptually AFAIR, although some rounding / effective values caching could possibly affect the final values.) > so the old D target leaves very little > room below the upper bound of the 20% tolerance. On 6.12 x86_64, 105 > iterations of memcontrol03 across ext2, ext3, ext4, xfs and btrfs gave: > = > A/B/C 27.5M - 27.9M (old range 22.0M - 49.5M) > A/B/D 22.7M - 23.0M (old range 11.3M - 25.5M) > = > so A/B/D is already at ~90% of the old limit and small variations in > reclaim push it over. Passing runs on 6.4 ppc64le show the same > picture for both tests (C 22.6M - 32.0M, D 17.6M - 24.2M). > = > Switch to the model values. Keep the 20% tolerance, which is already > at least as wide as the kselftest's; kernel commit d2def68ae06a > ("selftests: memcg: increase error tolerance of child memory.current > check in test_memcg_protection()") raised the kselftest tolerances to > 15% (C) and 20% (D) for the same kind of sporadic failures. Makes sense to sync this with the kernel variant. Reviewed-by: Michal Koutn=FD > This doesn't change the outcome where C is reclaimed far below D while > the unprotected A/B/F keeps its pagecache (seen e.g. on ppc64le with > C ~=3D 6M and F ~=3D 13M). That is a protection failure the tests should > keep reporting. I presume you refer the same reclaim mode "collapse" that was tackled in 7e19705f7 ("memcg/memcontrol04: Fix judgment for recursive_protection") (there it was only for unexpected events but that could be connected with the unexpected final F.memory.current). It is nothing new, correct? Thanks, Michal -- = Mailing list info: https://lists.linux.it/listinfo/ltp