lkml.org 
[lkml]   [2018]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v13 10/11] cpuset: Add documentation about the new "cpuset.sched.partition" flag
    Date
    The cgroup-v2.rst file is updated to document the purpose of the new
    "cpuset.sched.partition" flag and how its usage.

    Signed-off-by: Waiman Long <longman@redhat.com>
    ---
    Documentation/admin-guide/cgroup-v2.rst | 66 +++++++++++++++++++++++++++++++++
    1 file changed, 66 insertions(+)

    diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
    index 533e85c..178cda4 100644
    --- a/Documentation/admin-guide/cgroup-v2.rst
    +++ b/Documentation/admin-guide/cgroup-v2.rst
    @@ -1686,6 +1686,72 @@ Cpuset Interface Files

    Its value will be affected by memory nodes hotplug events.

    + cpuset.sched.partition
    + A read-write single value file which exists on non-root
    + cpuset-enabled cgroups. It accepts either "0" (off) or "1"
    + (on) when written to. This flag is set and owned by the
    + parent cgroup.
    +
    + If set, it indicates that the current cgroup is the root of a
    + new partition or scheduling domain that comprises itself and
    + all its descendants except those that are separate partition
    + roots themselves and their descendants. The root cgroup is
    + always a partition 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 a partition root.
    + 3) The "cpuset.cpus" is also a proper subset of the parent's
    + "cpuset.cpus.effective".
    + 4) 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.
    +
    + A parent partition cannot distribute all its CPUs to its
    + child partitions. There must be at least one cpu left in the
    + parent partition.
    +
    + Once becoming a partition root, changes to "cpuset.cpus" is
    + generally allowed as long as the first condition above is true,
    + the change will not take away all the CPUs from the parent
    + partition and the new "cpuset.cpus" value is a superset of its
    + children's "cpuset.cpus" values.
    +
    + Sometimes, external factors like changes to ancestors'
    + "cpuset.cpus" or cpu hotplug can cause the state of the partition
    + root to change. On read, the "cpuset.sched.partition" file
    + can show the following values.
    +
    + "0" Not a partition root
    + "1" Partition root
    + "-1" Erroneous partition root
    +
    + It is a partition root if the first 2 partition root conditions
    + above are true and at least one CPU from "cpuset.cpus" is
    + granted by the parent cgroup.
    +
    + A partition root can become an erroneous partition root if none
    + of CPUs requested in "cpuset.cpus" can be granted by the parent
    + cgroup or the parent cgroup is no longer a partition root.
    + In this case, it is not a real partition even though the
    + restriction of the first partition root condition above will
    + still apply. All the tasks in the cgroup will be migrated to
    + the nearest ancestor partition.
    +
    + An erroneous partition root can be transitioned back to a real
    + partition root if at least one of the requested CPUs can now be
    + granted by its parent. In this case, the tasks will be migrated
    + back to the newly created partition. Clearing the partition
    + flag of an erroneous partition root is always allowed even if
    + child cpusets are present.
    +

    Device controller
    -----------------
    --
    1.8.3.1
    \
     
     \ /
      Last update: 2018-10-12 19:57    [W:2.680 / U:0.288 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site