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SubjectRe: [PATCH v9 2/7] cpuset: Add new v2 cpuset.sched.domain_root flag
Hi,

On 29/05/18 09:41, Waiman Long wrote:

[...]

> + cpuset.sched.domain_root
> + A read-write single value file which exists on non-root
> + cpuset-enabled cgroups. It is a binary value flag that accepts
> + either "0" (off) or "1" (on). This flag is set by the parent
> + and is not delegatable.
> +
> + If set, it indicates that the current cgroup is the root of a
> + new scheduling domain or partition that comprises itself and
> + all its descendants except those that are scheduling domain
> + roots themselves and their descendants. The root cgroup is
> + always a scheduling domain root.
> +
> + There are constraints on where this flag can be set. It can
> + only be set in a cgroup if all the following conditions are true.
> +
> + 1) The "cpuset.cpus" is not empty and the list of CPUs are
> + exclusive, i.e. they are not shared by any of its siblings.
> + 2) The parent cgroup is also a scheduling domain root.
> + 3) There is no child cgroups with cpuset enabled. This is
> + for eliminating corner cases that have to be handled if such
> + a condition is allowed.
> +
> + Setting this flag will take the CPUs away from the effective
> + CPUs of the parent cgroup. Once it is set, this flag cannot
> + be cleared if there are any child cgroups with cpuset enabled.
> + Further changes made to "cpuset.cpus" is allowed as long as
> + the first condition above is still true.

IIUC, with the configuration below

cpuset.cpus.effective:6-11
cgroup.controllers:cpuset
cpuset.mems.effective:0-1
cgroup.subtree_control:cpuset
g1/cpuset.cpus.effective:0-5
g1/cgroup.controllers:cpuset
g1/cpuset.sched.load_balance:1
g1/cpuset.mems.effective:0-1
g1/cpuset.cpus:0-5
g1/cpuset.sched.domain_root:1
user.slice/cpuset.cpus.effective:6-11
user.slice/cgroup.controllers:cpuset
user.slice/cpuset.sched.load_balance:1
user.slice/cpuset.mems.effective:0-1
user.slice/cpuset.cpus:6-11
user.slice/cpuset.sched.domain_root:0
init.scope/cpuset.cpus.effective:6-11
init.scope/cgroup.controllers:cpuset
init.scope/cpuset.sched.load_balance:1
init.scope/cpuset.mems.effective:0-1
init.scope/cpuset.cpus:6-11
init.scope/cpuset.sched.domain_root:0
system.slice/cpuset.cpus.effective:6-11
system.slice/cgroup.controllers:cpuset
system.slice/cpuset.sched.load_balance:1
system.slice/cpuset.mems.effective:0-1
system.slice/cpuset.cpus:6-11
system.slice/cpuset.sched.domain_root:0
machine.slice/cpuset.cpus.effective:6-11
machine.slice/cgroup.controllers:cpuset
machine.slice/cpuset.sched.load_balance:1
machine.slice/cpuset.mems.effective:0-1
machine.slice/cpuset.cpus:6-11
machine.slice/cpuset.sched.domain_root:0

I should be able to

# echo 0-4 >g1/cpuset.cpus

?

It doesn't let me.

I'm not sure we actually want to allow that, but that's what would I
expect as per your text above.

Thanks,

- Juri

BTW: thanks a lot for your prompt feedback and hope it's OK if I keep
playing and asking questions. :)

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