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Mon, 09 Sep 2024 05:16:20 -0700 (PDT) From: Celeste Liu X-Google-Original-From: Celeste Liu Message-ID: <9e364ae4-dc2c-4efa-8611-462218402a5d@gmail.com> Date: Mon, 9 Sep 2024 20:14:16 +0800 Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] riscv: defconfig: drop RT_GROUP_SCHED=y To: Conor Dooley Cc: 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 , 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 References: <20240823-fix-riscv-rt_group_sched-v2-0-e4dbae24f7e1@gmail.com> <20240823-fix-riscv-rt_group_sched-v2-1-e4dbae24f7e1@gmail.com> <20240909-gave-celtic-af2ea8bc38d5@wendy> Content-Language: en-GB-large In-Reply-To: <20240909-gave-celtic-af2ea8bc38d5@wendy> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024-09-09 19:53, Conor Dooley wrote: > On Fri, Aug 23, 2024 at 01:43:26AM +0800, Celeste Liu wrote: >> Commit ba6cfef057e1 ("riscv: enable Docker requirements in defconfig") >> introduced it because of Docker, but Docker has removed this requirement >> since [1] (2023-04-19). >> >> 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.[2] >> >> 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.[3] >> >> [1]: https://github.com/moby/moby/commit/005150ed69c540fb0b5323e0f2208608c1204536 >> [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700 >> [3]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383 >> >> Fixes: ba6cfef057e1 ("riscv: enable Docker requirements in defconfig") > > I don't think this fixes tag is suitable, the commit you cite in > moby/docker is a year younger than the one in the fixes tag, so it was > correct at the time it was written. I think the fixes tag should just be > removed, since that commit was not wrong. Or am I missing something? The Docker commit I cited introduce the fix, not the bug. So it should be later than commit in fixes tag, otherwise Heinrich Schuchardt won't pick the wrong config from upstream. Timeline is: 1) 2015-06-19 Qiang Huang introduce RT_GROUP_SCHED check in Docker.[1] 2) 2022-06-08 Heinrich Schuchardt pick this to defconfig in commit in fixes tag. 3) 2023-04-19 Florian Schmaus remove this requirement from Docker in commit I cited. [1]: https://github.com/moby/moby/commit/fb85a99f5899df7475ba6b1ac4b2e1d32974eca2 > >> Signed-off-by: Celeste Liu >> --- >> arch/riscv/configs/defconfig | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig >> index 12dc8c73a8ac..de85c3ab261e 100644 >> --- a/arch/riscv/configs/defconfig >> +++ b/arch/riscv/configs/defconfig >> @@ -9,7 +9,6 @@ CONFIG_CGROUPS=y >> CONFIG_MEMCG=y >> CONFIG_CGROUP_SCHED=y >> CONFIG_CFS_BANDWIDTH=y >> -CONFIG_RT_GROUP_SCHED=y >> CONFIG_CGROUP_PIDS=y >> CONFIG_CGROUP_FREEZER=y >> CONFIG_CGROUP_HUGETLB=y >> >> -- >> 2.46.0 >>