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Thu, 22 Aug 2024 10:43:38 -0700 (PDT) From: Celeste Liu X-Google-Original-From: Celeste Liu Date: Fri, 23 Aug 2024 01:43:27 +0800 Subject: [PATCH v2 2/4] loongarch: defconfig: drop RT_GROUP_SCHED=y Precedence: bulk X-Mailing-List: linux-omap@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240823-fix-riscv-rt_group_sched-v2-2-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, Xi Ruoyao , Celeste Liu X-Mailer: b4 0.14.1 X-Developer-Signature: v=1; a=openpgp-sha256; l=1676; i=CoelacanthusHex@gmail.com; h=from:subject:message-id; bh=BD75Xt3LZKpr2Q5IcAd6LQbXDWkdD5S9pnl1NWkD0aY=; b=owJ4nJvAy8zAJfY4pvNJRPo6U8bTakkMaccrDq7cWv9HKpm1gp9XuSSxq8t74rLzH8Iuc9/9Z V6+kdfkhV1HKQuDGBeDrJgii9jOp6+XlT76sIzXZAbMHFYmkCEMXJwCMBH5fob/mZs/PD5ma8Hx 8F7zO+Gcfce/RpUvkP7W1qScI/C0aYLCVYb/pR2XVnbPdNm4oDwvfcO+zZx8fjqb7h2UvJJdVsM b5lHKCADITk6N 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 Reviewed-by: Xi Ruoyao Signed-off-by: Celeste Liu --- arch/loongarch/configs/loongson3_defconfig | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig index b4252c357c8e..4d93adb3f1a2 100644 --- a/arch/loongarch/configs/loongson3_defconfig +++ b/arch/loongarch/configs/loongson3_defconfig @@ -23,7 +23,6 @@ CONFIG_NUMA_BALANCING=y CONFIG_MEMCG=y CONFIG_BLK_CGROUP=y CONFIG_CFS_BANDWIDTH=y -CONFIG_RT_GROUP_SCHED=y CONFIG_CGROUP_PIDS=y CONFIG_CGROUP_RDMA=y CONFIG_CGROUP_FREEZER=y