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Thu, 22 Aug 2024 10:43:41 -0700 (PDT) From: Celeste Liu X-Google-Original-From: Celeste Liu Date: Fri, 23 Aug 2024 01:43:28 +0800 Subject: [PATCH v2 3/4] sh: defconfig: drop RT_GROUP_SCHED=y from sdk7786/urquell Precedence: bulk X-Mailing-List: linux-sh@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240823-fix-riscv-rt_group_sched-v2-3-e4dbae24f7e1@gmail.com> References: <20240823-fix-riscv-rt_group_sched-v2-0-e4dbae24f7e1@gmail.com> In-Reply-To: <20240823-fix-riscv-rt_group_sched-v2-0-e4dbae24f7e1@gmail.com> To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Anup Patel , Heinrich Schuchardt , Huacai Chen , WANG Xuerui , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Russell King , Florian Fainelli , Broadcom internal kernel review list , Ray Jui , Scott Branden , Tony Lindgren , Thierry Reding , Jonathan Hunter Cc: Palmer Dabbelt , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-sh@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-tegra@vger.kernel.org, Celeste Liu X-Mailer: b4 0.14.1 X-Developer-Signature: v=1; a=openpgp-sha256; l=2031; i=CoelacanthusHex@gmail.com; h=from:subject:message-id; bh=RtVPfBukDdiWXFe+rES/vpRLMHkhNnaCFx7uCSJVdVE=; b=owJ4nJvAy8zAJfY4pvNJRPo6U8bTakkMaccrDrHXhbvqv0j2K04OUp6r9c3yjL7wmfkK3ed0L wiLJwVfOdVRysIgxsUgK6bIIrbz6etlpY8+LOM1mQEzh5UJZAgDF6cATIR5CcP/uAsdETX3d4jM P1D0MeoGY0/w5qWbQibevqlWcn6F0szobQx/ZR6s/XP6xDnB6RkyIt+j14R9+7s1gD9Tsy1IxPC t2qsvjAD/Nk5/ X-Developer-Key: i=CoelacanthusHex@gmail.com; a=openpgp; fpr=892EBC7DC392DFF9C9C03F1D15F4180E73787863 For cgroup v1, if turned on, and there's any cgroup in the "cpu" hierarchy it needs an RT budget assigned, otherwise the processes in it will not be able to get RT at all. The problem with RT group scheduling is that it requires the budget assigned but there's no way we could assign a default budget, since the values to assign are both upper and lower time limits, are absolute, and need to be sum up to < 1 for each individal cgroup. That means we cannot really come up with values that would work by default in the general case.[1] For cgroup v2, it's almost unusable as well. If it turned on, the cpu controller can only be enabled when all RT processes are in the root cgroup. But it will lose the benefits of cgroup v2 if all RT process were placed in the same cgroup. Red Hat, Gentoo, Arch Linux and Debian all disable it. systemd also doesn't support it.[2] [1]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700 [2]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383 Signed-off-by: Celeste Liu --- arch/sh/configs/sdk7786_defconfig | 1 - arch/sh/configs/urquell_defconfig | 1 - 2 files changed, 2 deletions(-) diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig index 7b427c17fbfe..3599b1683593 100644 --- a/arch/sh/configs/sdk7786_defconfig +++ b/arch/sh/configs/sdk7786_defconfig @@ -17,7 +17,6 @@ CONFIG_CPUSETS=y CONFIG_CGROUP_CPUACCT=y CONFIG_CGROUP_MEMCG=y CONFIG_CGROUP_SCHED=y -CONFIG_RT_GROUP_SCHED=y CONFIG_BLK_CGROUP=y CONFIG_RELAY=y CONFIG_NAMESPACES=y diff --git a/arch/sh/configs/urquell_defconfig b/arch/sh/configs/urquell_defconfig index 00ef62133b04..9cf4a719001e 100644 --- a/arch/sh/configs/urquell_defconfig +++ b/arch/sh/configs/urquell_defconfig @@ -15,7 +15,6 @@ CONFIG_CPUSETS=y CONFIG_CGROUP_CPUACCT=y CONFIG_CGROUP_MEMCG=y CONFIG_CGROUP_SCHED=y -CONFIG_RT_GROUP_SCHED=y CONFIG_BLK_DEV_INITRD=y CONFIG_PROFILING=y CONFIG_MODULES=y