From: Thierry Reding <thierry.reding@gmail.com>
To: Celeste Liu <coelacanthushex@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org>,
Anup Patel <anup@brainfault.org>,
Heinrich Schuchardt <heinrich.schuchardt@canonical.com>,
Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
Russell King <linux@armlinux.org.uk>,
Florian Fainelli <florian.fainelli@broadcom.com>,
Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com>,
Ray Jui <rjui@broadcom.com>,
Scott Branden <sbranden@broadcom.com>,
Tony Lindgren <tony@atomide.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
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,
Stefan Wahren <wahrenst@gmx.net>,
Kevin Hilman <khilman@baylibre.com>
Subject: Re: [PATCH v3 4/4] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2835/tegra/omap2plus
Date: Thu, 24 Oct 2024 19:10:23 +0200 [thread overview]
Message-ID: <6m77wg6b76abyk2ebfniayxvrabvzur7onwar4isajb6tvfxbv@7a24p2xkmevj> (raw)
In-Reply-To: <20240910-fix-riscv-rt_group_sched-v3-4-486e75e5ae6d@gmail.com>
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On Tue, Sep 10, 2024 at 08:51:10PM +0800, Celeste Liu wrote:
> Commit 673ce00c5d6c ("ARM: omap2plus_defconfig: Add support for distros
> with systemd") said it's because of recommendation from systemd. But
> systemd changed their recommendation later.[1]
>
> 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.
>
> [1]: https://github.com/systemd/systemd/commit/f4e74be1856b3ac058acbf1be321c31d5299f69f
> [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700
>
> Tested-by: Stefan Wahren <wahrenst@gmx.net>
> Acked-by: Kevin Hilman <khilman@baylibre.com>
> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
> ---
> arch/arm/configs/bcm2835_defconfig | 1 -
> arch/arm/configs/omap2plus_defconfig | 1 -
> arch/arm/configs/tegra_defconfig | 1 -
> 3 files changed, 3 deletions(-)
Any idea who will want to pick this up? Probably something the ARM SoC
maintainers can do directly, in which case:
Acked-by: Thierry Reding <treding@nvidia.com>
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prev parent reply other threads:[~2024-10-24 17:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-10 12:51 [PATCH v3 0/4] defconfig: drop RT_GROUP_SCHED=y Celeste Liu
2024-09-10 12:51 ` [PATCH v3 1/4] riscv: " Celeste Liu
2024-09-12 20:58 ` Charlie Jenkins
2024-09-10 12:51 ` [PATCH v3 2/4] loongarch: " Celeste Liu
2024-09-10 12:51 ` [PATCH v3 3/4] sh: defconfig: drop RT_GROUP_SCHED=y from sdk7786/urquell Celeste Liu
2024-09-10 12:51 ` [PATCH v3 4/4] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2835/tegra/omap2plus Celeste Liu
2024-10-24 17:10 ` Thierry Reding [this message]
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