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[90.182.211.1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a1787e8b2asm519755e9.6.2026.10.05.08.37.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Oct 2026 08:37:48 -0700 (PDT) Date: Mon, 5 Oct 2026 17:37:46 +0200 To: Wei Gao Message-ID: References: <20261004143332.25978-1-wegao@suse.com> <20261004143332.25978-3-wegao@suse.com> MIME-Version: 1.0 In-Reply-To: <20261004143332.25978-3-wegao@suse.com> X-Virus-Scanned: clamav-milter 1.0.9 at in-3.smtp.seeweb.it X-Virus-Status: Clean X-Content-Filtered-By: Mailman/MimeDel 2.1.29 Subject: Re: [LTP] [PATCH v1 2/2] memcontrol03, memcontrol04: Set protection on parent cgroups to prevent kswapd over-reclaim 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: ltp@lists.linux.it Content-Type: multipart/mixed; boundary="===============1748061619==" Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" --===============1748061619== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="uhhm57oyntxollre" Content-Disposition: inline --uhhm57oyntxollre Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v1 2/2] memcontrol03, memcontrol04: Set protection on parent cgroups to prevent kswapd over-reclaim MIME-Version: 1.0 Hello Wei. On Sun, Oct 04, 2026 at 02:33:27PM +0000, Wei Gao wrote: > On NUMA systems (observed on PowerPC), allocating memory can trigger > node-level memory pressure, waking up kswapd when free pages fall below > the low watermark on a node. >=20 > In cgroup v2, both hard protection (memory.min) and best-effort protection > (memory.low) are hierarchical and calculated top-down: effective > protection of descendant cgroups is bounded by their ancestors' protection > values. When LTP runs inside an existing cgroup hierarchy, ancestor cgrou= ps > above the test root have memory.min and memory.low set to 0. Note that this is expected behavior of protection and the test is meant to work "relatively" with its own pressure source and target [1]. > As a result, when kswapd performs node-level background reclaim from the > root cgroup downwards, ancestor cgroups without protection provide no > protection boundary. kswapd reclaims pages from descendant leaf cgroups > regardless of their local memory.min / memory.low settings, causing > memcontrol03 and memcontrol04 to fail with over-reclaim: Generally, this is not specific to this test -- it is because it the whole host is overcommitted (edit: as I see the NUMA info below it could be perhaps that only individual nodes are too small). So I wonder could this be ensured at higher level -- something that sets up the environment of the individual runners (e.g. reduce parallelism, partition the system with memory limits or as a variant configure generic memory protection)? WDYT? Michal [1] https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#recla= im-protection --uhhm57oyntxollre-- --===============1748061619== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- Mailing list info: https://lists.linux.it/listinfo/ltp --===============1748061619==--