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Diffstat (limited to 'Documentation/admin-guide/cgroup-v2.rst')
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 178 |
1 files changed, 142 insertions, 36 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index b26b5274eaaf..3f85254f3cef 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -210,6 +210,35 @@ cgroup v2 currently supports the following mount options. relying on the original semantics (e.g. specifying bogusly high 'bypass' protection values at higher tree levels). + memory_hugetlb_accounting + Count HugeTLB memory usage towards the cgroup's overall + memory usage for the memory controller (for the purpose of + statistics reporting and memory protetion). This is a new + behavior that could regress existing setups, so it must be + explicitly opted in with this mount option. + + A few caveats to keep in mind: + + * There is no HugeTLB pool management involved in the memory + controller. The pre-allocated pool does not belong to anyone. + Specifically, when a new HugeTLB folio is allocated to + the pool, it is not accounted for from the perspective of the + memory controller. It is only charged to a cgroup when it is + actually used (for e.g at page fault time). Host memory + overcommit management has to consider this when configuring + hard limits. In general, HugeTLB pool management should be + done via other mechanisms (such as the HugeTLB controller). + * Failure to charge a HugeTLB folio to the memory controller + results in SIGBUS. This could happen even if the HugeTLB pool + still has pages available (but the cgroup limit is hit and + reclaim attempt fails). + * Charging HugeTLB memory towards the memory controller affects + memory protection and reclaim dynamics. Any userspace tuning + (of low, min limits for e.g) needs to take this into account. + * HugeTLB pages utilized while this option is not selected + will not be tracked by the memory controller (even if cgroup + v2 is remounted later on). + Organizing Processes and Threads -------------------------------- @@ -364,6 +393,13 @@ constraint, a threaded controller must be able to handle competition between threads in a non-leaf cgroup and its child cgroups. Each threaded controller defines how such competitions are handled. +Currently, the following controllers are threaded and can be enabled +in a threaded cgroup:: + +- cpu +- cpuset +- perf_event +- pids [Un]populated Notification -------------------------- @@ -1532,6 +1568,15 @@ PAGE_SIZE multiple when read back. collapsing an existing range of pages. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE is not set. + thp_swpout (npn) + Number of transparent hugepages which are swapout in one piece + without splitting. + + thp_swpout_fallback (npn) + Number of transparent hugepages which were split before swapout. + Usually because failed to allocate some continuous swap space + for the huge page. + memory.numa_stat A read-only nested-keyed file which exists on non-root cgroups. @@ -2023,7 +2068,7 @@ IO Priority ~~~~~~~~~~~ A single attribute controls the behavior of the I/O priority cgroup policy, -namely the blkio.prio.class attribute. The following values are accepted for +namely the io.prio.class attribute. The following values are accepted for that attribute: no-change @@ -2052,9 +2097,11 @@ The following numerical values are associated with the I/O priority policies: +----------------+---+ | no-change | 0 | +----------------+---+ -| rt-to-be | 2 | +| promote-to-rt | 1 | +----------------+---+ -| all-to-idle | 3 | +| restrict-to-be | 2 | ++----------------+---+ +| idle | 3 | +----------------+---+ The numerical value that corresponds to each I/O priority class is as follows: @@ -2074,7 +2121,7 @@ The algorithm to set the I/O priority class for a request is as follows: - If I/O priority class policy is promote-to-rt, change the request I/O priority class to IOPRIO_CLASS_RT and change the request I/O priority level to 4. -- If I/O priorityt class is not promote-to-rt, translate the I/O priority +- If I/O priority class policy is not promote-to-rt, translate the I/O priority class policy into a number, then change the request I/O priority class into the maximum of the I/O priority class policy number and the numerical I/O priority class. @@ -2226,6 +2273,49 @@ Cpuset Interface Files Its value will be affected by memory nodes hotplug events. + cpuset.cpus.exclusive + A read-write multiple values file which exists on non-root + cpuset-enabled cgroups. + + It lists all the exclusive CPUs that are allowed to be used + to create a new cpuset partition. Its value is not used + unless the cgroup becomes a valid partition root. See the + "cpuset.cpus.partition" section below for a description of what + a cpuset partition is. + + When the cgroup becomes a partition root, the actual exclusive + CPUs that are allocated to that partition are listed in + "cpuset.cpus.exclusive.effective" which may be different + from "cpuset.cpus.exclusive". If "cpuset.cpus.exclusive" + has previously been set, "cpuset.cpus.exclusive.effective" + is always a subset of it. + + Users can manually set it to a value that is different from + "cpuset.cpus". The only constraint in setting it is that the + list of CPUs must be exclusive with respect to its sibling. + + For a parent cgroup, any one of its exclusive CPUs can only + be distributed to at most one of its child cgroups. Having an + exclusive CPU appearing in two or more of its child cgroups is + not allowed (the exclusivity rule). A value that violates the + exclusivity rule will be rejected with a write error. + + The root cgroup is a partition root and all its available CPUs + are in its exclusive CPU set. + + cpuset.cpus.exclusive.effective + A read-only multiple values file which exists on all non-root + cpuset-enabled cgroups. + + This file shows the effective set of exclusive CPUs that + can be used to create a partition root. The content of this + file will always be a subset of "cpuset.cpus" and its parent's + "cpuset.cpus.exclusive.effective" if its parent is not the root + cgroup. It will also be a subset of "cpuset.cpus.exclusive" + if it is set. If "cpuset.cpus.exclusive" is not set, it is + treated to have an implicit value of "cpuset.cpus" in the + formation of local partition. + cpuset.cpus.partition A read-write single value file which exists on non-root cpuset-enabled cgroups. This flag is owned by the parent cgroup @@ -2239,26 +2329,41 @@ Cpuset Interface Files "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". + A cpuset partition is a collection of cpuset-enabled cgroups with + a partition root at the top of the hierarchy and its descendants + except those that are separate partition roots themselves and + their descendants. A partition has exclusive access to the + set of exclusive CPUs allocated to it. Other cgroups outside + of that partition cannot use any CPUs in that set. + + There are two types of partitions - local and remote. A local + partition is one whose parent cgroup is also a valid partition + root. A remote partition is one whose parent cgroup is not a + valid partition root itself. Writing to "cpuset.cpus.exclusive" + is optional for the creation of a local partition as its + "cpuset.cpus.exclusive" file will assume an implicit value that + is the same as "cpuset.cpus" if it is not set. Writing the + proper "cpuset.cpus.exclusive" values down the cgroup hierarchy + before the target partition root is mandatory for the creation + of a remote partition. + + Currently, a remote partition cannot be created under a local + partition. All the ancestors of a remote partition root except + the root cgroup cannot be a partition root. + + 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. + partition or scheduling domain. The set of exclusive CPUs is + determined by the value of its "cpuset.cpus.exclusive.effective". - When set to "isolated", the CPUs in that partition root will + When set to "isolated", the CPUs in that partition 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 @@ -2281,37 +2386,33 @@ Cpuset Interface Files 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 + For a local partition root to be 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 + 1) The parent cgroup is a valid partition root. + 2) The "cpuset.cpus.exclusive.effective" file cannot be empty, + though it may contain offline CPUs. + 3) 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 remote partition root to be valid, all the above conditions + except the first one must be met. - 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 - sibling partitions with conflicting cpuset.cpus values. So - care must be taking in changing "cpuset.cpus". + External events like hotplug or changes to "cpuset.cpus" or + "cpuset.cpus.exclusive" 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". A valid non-root parent partition may distribute out all its CPUs - to its child partitions when there is no task associated with it. + to its child local 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 + Care must be taken to change a valid partition root to "member" + as all its child local 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". + value in "cpuset.cpus" or "cpuset.cpus.exclusive". Poll and inotify events are triggered whenever the state of "cpuset.cpus.partition" changes. That includes changes caused @@ -2321,6 +2422,11 @@ Cpuset Interface Files to "cpuset.cpus.partition" without the need to do continuous polling. + A user can pre-configure certain CPUs to an isolated state + with load balancing disabled at boot time with the "isolcpus" + kernel boot command line option. If those CPUs are to be put + into a partition, they have to be used in an isolated partition. + Device controller ----------------- |