[PATCH 0/6] defconfig: drop RT_GROUP_SCHED=y

[PATCH 0/6] defconfig: drop RT_GROUP_SCHED=y

[Celeste Liu]

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]

I leave tools/testing/selftests/bpf/config.{s390x,aarch64} untouched because
I don't whether bpf testing requires it.

[1]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700
[2]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383


Celeste Liu (6):
  riscv: defconfig: drop RT_GROUP_SCHED=y
  loongarch: defconfig: drop RT_GROUP_SCHED=y
  mips: defconfig: drop RT_GROUP_SCHED=y from generic/db1xxx/eyeq5
  powerpc: defconfig: drop RT_GROUP_SCHED=y from ppc6xx_defconfig
  sh: defconfig: drop RT_GROUP_SCHED=y from sdk7786/urquell
  arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

 arch/arm/configs/bcm2835_defconfig         | 1 -
 arch/arm/configs/omap2plus_defconfig       | 1 -
 arch/arm/configs/tegra_defconfig           | 1 -
 arch/loongarch/configs/loongson3_defconfig | 1 -
 arch/mips/configs/db1xxx_defconfig         | 1 -
 arch/mips/configs/eyeq5_defconfig          | 1 -
 arch/mips/configs/generic_defconfig        | 1 -
 arch/powerpc/configs/ppc6xx_defconfig      | 1 -
 arch/riscv/configs/defconfig               | 1 -
 arch/sh/configs/sdk7786_defconfig          | 1 -
 arch/sh/configs/urquell_defconfig          | 1 -
 11 files changed, 11 deletions(-)

-- 
2.45.1

[PATCH 1/6] riscv: defconfig: drop RT_GROUP_SCHED=y

[Celeste Liu]

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")
Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
---
 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
-- 
2.45.1

[PATCH 2/6] loongarch: defconfig: drop RT_GROUP_SCHED=y

[Celeste Liu]

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

Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
---
 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
-- 
2.45.1

Re: [PATCH 2/6] loongarch: defconfig: drop RT_GROUP_SCHED=y

[Xi Ruoyao]

On Thu, 2024-05-30 at 19:19 +0800, Celeste Liu wrote:
> 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
> 
> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>

As a distro maintainer who had once been bitten by this option:

Reviewed-by: Xi Ruoyao <xry111@xry111.site>

> ---
>  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

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University

[PATCH 3/6] mips: defconfig: drop RT_GROUP_SCHED=y from generic/db1xxx/eyeq5

[Celeste Liu]

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

Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
---
 arch/mips/configs/db1xxx_defconfig  | 1 -
 arch/mips/configs/eyeq5_defconfig   | 1 -
 arch/mips/configs/generic_defconfig | 1 -
 3 files changed, 3 deletions(-)

diff --git a/arch/mips/configs/db1xxx_defconfig b/arch/mips/configs/db1xxx_defconfig
index b2d9253ff786..6eff21ff15d5 100644
--- a/arch/mips/configs/db1xxx_defconfig
+++ b/arch/mips/configs/db1xxx_defconfig
@@ -12,7 +12,6 @@ CONFIG_MEMCG=y
 CONFIG_BLK_CGROUP=y
 CONFIG_CGROUP_SCHED=y
 CONFIG_CFS_BANDWIDTH=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CGROUP_CPUACCT=y
diff --git a/arch/mips/configs/eyeq5_defconfig b/arch/mips/configs/eyeq5_defconfig
index c35c29a4d479..3794707c9522 100644
--- a/arch/mips/configs/eyeq5_defconfig
+++ b/arch/mips/configs/eyeq5_defconfig
@@ -8,7 +8,6 @@ CONFIG_IKCONFIG_PROC=y
 CONFIG_MEMCG=y
 CONFIG_BLK_CGROUP=y
 CONFIG_CFS_BANDWIDTH=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_PIDS=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CPUSETS=y
diff --git a/arch/mips/configs/generic_defconfig b/arch/mips/configs/generic_defconfig
index 071e2205c7ed..fa916407bdd4 100644
--- a/arch/mips/configs/generic_defconfig
+++ b/arch/mips/configs/generic_defconfig
@@ -5,7 +5,6 @@ CONFIG_IKCONFIG_PROC=y
 CONFIG_MEMCG=y
 CONFIG_BLK_CGROUP=y
 CONFIG_CFS_BANDWIDTH=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_PIDS=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CPUSETS=y
-- 
2.45.1

Re: [PATCH 3/6] mips: defconfig: drop RT_GROUP_SCHED=y from generic/db1xxx/eyeq5

[Thomas Bogendoerfer]

On Thu, May 30, 2024 at 07:19:51PM +0800, Celeste Liu wrote:
> 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
> 
> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
> ---
>  arch/mips/configs/db1xxx_defconfig  | 1 -
>  arch/mips/configs/eyeq5_defconfig   | 1 -
>  arch/mips/configs/generic_defconfig | 1 -
>  3 files changed, 3 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

[PATCH 4/6] powerpc: defconfig: drop RT_GROUP_SCHED=y from ppc6xx_defconfig

[Celeste Liu]

Commit 6e5f1537833a ("powerpc: Add a 6xx defconfig") said it was copied
from fedore's ppc32 defconfig, but at least since 2015-06-10, Fedora has
dropped this option.[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.[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.

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

Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
---
 arch/powerpc/configs/ppc6xx_defconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/powerpc/configs/ppc6xx_defconfig b/arch/powerpc/configs/ppc6xx_defconfig
index 66c7b28d7450..c06344db0eb3 100644
--- a/arch/powerpc/configs/ppc6xx_defconfig
+++ b/arch/powerpc/configs/ppc6xx_defconfig
@@ -12,7 +12,6 @@ CONFIG_TASK_XACCT=y
 CONFIG_TASK_IO_ACCOUNTING=y
 CONFIG_CGROUPS=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_USER_NS=y
-- 
2.45.1

[PATCH 5/6] sh: defconfig: drop RT_GROUP_SCHED=y from sdk7786/urquell

[Celeste Liu]

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

Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
---
 arch/sh/configs/sdk7786_defconfig | 1 -
 arch/sh/configs/urquell_defconfig | 1 -
 2 files changed, 2 deletions(-)

diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig
index 7b427c17fbfe..3599b1683593 100644
--- a/arch/sh/configs/sdk7786_defconfig
+++ b/arch/sh/configs/sdk7786_defconfig
@@ -17,7 +17,6 @@ CONFIG_CPUSETS=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_BLK_CGROUP=y
 CONFIG_RELAY=y
 CONFIG_NAMESPACES=y
diff --git a/arch/sh/configs/urquell_defconfig b/arch/sh/configs/urquell_defconfig
index 00ef62133b04..9cf4a719001e 100644
--- a/arch/sh/configs/urquell_defconfig
+++ b/arch/sh/configs/urquell_defconfig
@@ -15,7 +15,6 @@ CONFIG_CPUSETS=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_PROFILING=y
 CONFIG_MODULES=y
-- 
2.45.1

[PATCH 6/6] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

[Celeste Liu]

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

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(-)

diff --git a/arch/arm/configs/bcm2835_defconfig b/arch/arm/configs/bcm2835_defconfig
index b5f0bd8dd536..27dc3bf6b124 100644
--- a/arch/arm/configs/bcm2835_defconfig
+++ b/arch/arm/configs/bcm2835_defconfig
@@ -7,7 +7,6 @@ CONFIG_BSD_PROCESS_ACCT=y
 CONFIG_BSD_PROCESS_ACCT_V3=y
 CONFIG_LOG_BUF_SHIFT=18
 CONFIG_CFS_BANDWIDTH=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CPUSETS=y
 CONFIG_CGROUP_DEVICE=y
diff --git a/arch/arm/configs/omap2plus_defconfig b/arch/arm/configs/omap2plus_defconfig
index 3a166c2f02bd..9cb265c8d414 100644
--- a/arch/arm/configs/omap2plus_defconfig
+++ b/arch/arm/configs/omap2plus_defconfig
@@ -13,7 +13,6 @@ CONFIG_MEMCG=y
 CONFIG_BLK_CGROUP=y
 CONFIG_CGROUP_SCHED=y
 CONFIG_CFS_BANDWIDTH=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CPUSETS=y
 CONFIG_CGROUP_DEVICE=y
diff --git a/arch/arm/configs/tegra_defconfig b/arch/arm/configs/tegra_defconfig
index d2a094ad360c..3a9bda2bf422 100644
--- a/arch/arm/configs/tegra_defconfig
+++ b/arch/arm/configs/tegra_defconfig
@@ -6,7 +6,6 @@ CONFIG_IKCONFIG=y
 CONFIG_IKCONFIG_PROC=y
 CONFIG_CGROUPS=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_DEBUG=y
-- 
2.45.1

Re: [PATCH 6/6] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

[Kevin Hilman]

Celeste Liu <coelacanthushex@gmail.com> writes:

> 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
>
> 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 -

For omap2plus_defconfig:

Acked-by: Kevin Hilman <khilman@baylibre.com>

Re: [PATCH 6/6] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

[Stefan Wahren]

Hi Celeste,

there is a typo in the subject line

s/bcm2855/bcm2835

Am 09.07.24 um 01:49 schrieb Kevin Hilman:
> Celeste Liu <coelacanthushex@gmail.com> writes:
>
>> 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
>>
>> 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 -
> For omap2plus_defconfig:
>
> Acked-by: Kevin Hilman <khilman@baylibre.com>
>
>
For bcm2835_defconfig:

Tested-by: Stefan Wahren <wahrenst@gmx.net>

Re: [PATCH 6/6] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

[Celeste Liu]

On 2024-07-09 20:26, Stefan Wahren wrote:
> Hi Celeste,
> 
> there is a typo in the subject line
> 
> s/bcm2855/bcm2835

Will be included in next version.

> 
> Am 09.07.24 um 01:49 schrieb Kevin Hilman:
>> Celeste Liu <coelacanthushex@gmail.com> writes:
>>
>>> 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
>>>
>>> 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 -
>> For omap2plus_defconfig:
>>
>> Acked-by: Kevin Hilman <khilman@baylibre.com>
>>
>>
> For bcm2835_defconfig:
> 
> Tested-by: Stefan Wahren <wahrenst@gmx.net>

Re: (subset) [PATCH 0/6] defconfig: drop RT_GROUP_SCHED=y

[Michael Ellerman]

On Thu, 30 May 2024 19:19:48 +0800, Celeste Liu wrote:
> 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]
> 
> [...]

Patch 4 applied to powerpc/next.

[4/6] powerpc: defconfig: drop RT_GROUP_SCHED=y from ppc6xx_defconfig
      https://git.kernel.org/powerpc/c/2bac6caee94e25f59ee47e2d365d7e07465089ba

cheers