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Message-ID: <ZuNV3ewTH63lb972@ghost>
Date: Thu, 12 Sep 2024 13:58:05 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Celeste Liu <coelacanthushex@...il.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
Anup Patel <anup@...infault.org>,
Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Rich Felker <dalias@...c.org>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
Russell King <linux@...linux.org.uk>,
Florian Fainelli <florian.fainelli@...adcom.com>,
Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
Tony Lindgren <tony@...mide.com>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
Palmer Dabbelt <palmer@...osinc.com>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
loongarch@...ts.linux.dev, linux-sh@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-rpi-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
linux-tegra@...r.kernel.org
Subject: Re: [PATCH v3 1/4] riscv: defconfig: drop RT_GROUP_SCHED=y
On Tue, Sep 10, 2024 at 08:51:07PM +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
>
> Acked-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
> Signed-off-by: Celeste Liu <CoelacanthusHex@...il.com>
Acked-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> arch/riscv/configs/defconfig | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
> index 12dc8c73a8acfaa5c8f442968a807de303428d9e..de85c3ab261e6d62b2089a3c89bdc9d1b34fa792 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
>
>
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