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Tue, 14 Jan 2025 15:42:09 -0500 (EST) From: Celeste Liu Date: Wed, 15 Jan 2025 04:41:21 +0800 Subject: [PATCH v4 2/4] loongarch: defconfig: drop RT_GROUP_SCHED=y Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250115-fix-riscv-rt_group_sched-v4-2-607606fe73a5@coelacanthus.name> References: <20250115-fix-riscv-rt_group_sched-v4-0-607606fe73a5@coelacanthus.name> In-Reply-To: <20250115-fix-riscv-rt_group_sched-v4-0-607606fe73a5@coelacanthus.name> 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 , Aaro Koskinen , Andreas Kemnade , Kevin Hilman , Roger Quadros 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 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1728; i=uwu@coelacanthus.name; h=from:subject:message-id; bh=faYQjbUe+IZ6IbLVoFWLES94wJ4yKdbIyLHK1P3reTU=; b=owJ4nJvAy8zAJeafov85RWVtBeNptSSG9LYzHNpGz3RdNkcq+138urdnco6HmLJOMKeQx8/dB x+9M/n57GhHKQuDGBeDrJgiS14Jy0/OS2e793Zs74KZw8oEMoSBi1MAJnIth5HhTFFkrOksz5Be jqCyI7OyWK2EubUnagjfyV8kYSe7ROMtw3+f+83SDSq+R6Y+//vmimFTUov/35ffOJ3jLvsv+PF vwT8+AA0oSNQ= X-Developer-Key: i=uwu@coelacanthus.name; 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 ne= ed to be sum up to < 1 for each individal cgroup. That means we cannot really com= e 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 contr= oller can only be enabled when all RT processes are in the root cgroup. But it wi= ll lose the benefits of cgroup v2 if all RT process were placed in the same cg= roup. 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=3D1229700 [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/co= nfigs/loongson3_defconfig index 4dffc90192f7816074c3bd4b55c12159d5757676..4387bcec8f484173e5367456a69= f6a7f03595d46 100644 --- a/arch/loongarch/configs/loongson3_defconfig +++ b/arch/loongarch/configs/loongson3_defconfig @@ -24,7 +24,6 @@ CONFIG_NUMA_BALANCING=3Dy CONFIG_MEMCG=3Dy CONFIG_BLK_CGROUP=3Dy CONFIG_CFS_BANDWIDTH=3Dy -CONFIG_RT_GROUP_SCHED=3Dy CONFIG_CGROUP_PIDS=3Dy CONFIG_CGROUP_RDMA=3Dy CONFIG_CGROUP_FREEZER=3Dy --=20 2.48.0