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Diffstat (limited to '')
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 184 |
1 files changed, 115 insertions, 69 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index be4a77baf784..dc254a3cb956 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -976,6 +976,29 @@ All cgroup core files are prefixed with "cgroup." killing cgroups is a process directed operation, i.e. it affects the whole thread-group. + cgroup.pressure + A read-write single value file that allowed values are "0" and "1". + The default is "1". + + Writing "0" to the file will disable the cgroup PSI accounting. + Writing "1" to the file will re-enable the cgroup PSI accounting. + + This control attribute is not hierarchical, so disable or enable PSI + accounting in a cgroup does not affect PSI accounting in descendants + and doesn't need pass enablement via ancestors from root. + + The reason this control attribute exists is that PSI accounts stalls for + each cgroup separately and aggregates it at each level of the hierarchy. + This may cause non-negligible overhead for some workloads when under + deep level of the hierarchy, in which case this control attribute can + be used to disable PSI accounting in the non-leaf cgroups. + + irq.pressure + A read-write nested-keyed file. + + Shows pressure stall information for IRQ/SOFTIRQ. See + :ref:`Documentation/accounting/psi.rst <psi>` for details. + Controllers =========== @@ -1355,6 +1378,11 @@ PAGE_SIZE multiple when read back. pagetables Amount of memory allocated for page tables. + sec_pagetables + Amount of memory allocated for secondary page tables, + this currently includes KVM mmu allocations on x86 + and arm64. + percpu (npn) Amount of memory used for storing per-cpu kernel data structures. @@ -2185,75 +2213,93 @@ Cpuset Interface Files It accepts only the following input values when written to. - ======== ================================ - "root" a partition root - "member" a non-root member of a partition - ======== ================================ - - When set to be a partition root, 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 a partition root 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 it to partition root will take the CPUs away from the - effective CPUs of the parent cgroup. Once it is set, this - file cannot be reverted back to "member" 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. - - ============== ============================== - "member" Non-root member of a partition - "root" Partition root - "root invalid" Invalid 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 invalid 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 itself. In this - case, it is not a real partition even though the restriction - of the first partition root condition above will still apply. - The cpu affinity of all the tasks in the cgroup will then be - associated with CPUs in the nearest ancestor partition. - - An invalid 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 cpu - affinity of all the tasks in the formerly invalid partition - will be associated to the CPUs of the newly formed partition. - Changing the partition state of an invalid partition root to - "member" is always allowed even if child cpusets are present. + ========== ===================================== + "member" Non-root member of a partition + "root" Partition root + "isolated" Partition root without load balancing + ========== ===================================== + + The root cgroup is always a partition root and its state + cannot be changed. All other non-root cgroups start out as + "member". + + When set to "root", 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. + + When set to "isolated", the CPUs in that partition root will + be in an isolated state without any load balancing from the + scheduler. Tasks placed in such a partition with multiple + CPUs should be carefully distributed and bound to each of the + individual CPUs for optimal performance. + + The value shown in "cpuset.cpus.effective" of a partition root + is the CPUs that the partition root can dedicate to a potential + new child partition root. The new child subtracts available + CPUs from its parent "cpuset.cpus.effective". + + A partition root ("root" or "isolated") can be in one of the + two possible states - valid or invalid. An invalid partition + root is in a degraded state where some state information may + be retained, but behaves more like a "member". + + All possible state transitions among "member", "root" and + "isolated" are allowed. + + On read, the "cpuset.cpus.partition" file can show the following + values. + + ============================= ===================================== + "member" Non-root member of a partition + "root" Partition root + "isolated" Partition root without load balancing + "root invalid (<reason>)" Invalid partition root + "isolated invalid (<reason>)" Invalid isolated partition root + ============================= ===================================== + + In the case of an invalid partition root, a descriptive string on + why the partition is invalid is included within parentheses. + + For a partition root to become valid, the following conditions + must be met. + + 1) The "cpuset.cpus" is exclusive with its siblings , i.e. they + are not shared by any of its siblings (exclusivity rule). + 2) The parent cgroup is a valid partition root. + 3) The "cpuset.cpus" is not empty and must contain at least + one of the CPUs from parent's "cpuset.cpus", i.e. they overlap. + 4) The "cpuset.cpus.effective" cannot be empty unless there is + no task associated with this partition. + + External events like hotplug or changes to "cpuset.cpus" can + cause a valid partition root to become invalid and vice versa. + Note that a task cannot be moved to a cgroup with empty + "cpuset.cpus.effective". + + For a valid partition root with the sibling cpu exclusivity + rule enabled, changes made to "cpuset.cpus" that violate the + exclusivity rule will invalidate the partition as well as its + sibiling partitions with conflicting cpuset.cpus values. So + care must be taking in changing "cpuset.cpus". + + A valid non-root parent partition may distribute out all its CPUs + to its child partitions when there is no task associated with it. + + Care must be taken to change a valid partition root to + "member" as all its child partitions, if present, will become + invalid causing disruption to tasks running in those child + partitions. These inactivated partitions could be recovered if + their parent is switched back to a partition root with a proper + set of "cpuset.cpus". + + Poll and inotify events are triggered whenever the state of + "cpuset.cpus.partition" changes. That includes changes caused + by write to "cpuset.cpus.partition", cpu hotplug or other + changes that modify the validity status of the partition. + This will allow user space agents to monitor unexpected changes + to "cpuset.cpus.partition" without the need to do continuous + polling. Device controller |