Documentation/admin-guide/cgroup-v2.rst

112 although there are utility controllers which serve purposes other than
125 processes which belong to the cgroups consisting the inclusive
144 controllers which support v2 and are not bound to a v1 hierarchy are
146 Controllers which are not in active use in the v2 hierarchy can be
210 Initially, only the root cgroup exists to which all processes belong.
217 "cgroup.procs".  When read, it lists the PIDs of all processes which
235 A cgroup which doesn't have any children or live processes can be
236 destroyed by removing the directory.  Note that a cgroup which doesn't
265 process belong to the same cgroup, which also serves as the resource
266 domain to host resource consumptions which are not specific to a
270 Controllers which support thread mode are called threaded controllers.
271 The ones which don't are called domain controllers.
276 of a threaded subtree, that is, the nearest ancestor which is not
288 can't have populated child cgroups which aren't threaded.  Because the
293 "cgroup.type" file which indicates whether the cgroup is a normal
294 domain, a domain which is serving as the domain of a threaded subtree,
318 C is created as a domain but isn't connected to a parent which can
321 these cases.  Operations which fail due to invalid topology use
349 threads in the cgroup and its descendants.  All consumptions which
361 Each non-root cgroup has a "cgroup.events" file which contains
387 Each cgroup has a "cgroup.controllers" file which lists all
398 Only controllers which are listed in "cgroup.controllers" can be
422 controller interface files - anything which doesn't start with
432 can only contain controllers which are enabled in the parent's
443 only domain cgroups which don't contain any processes can have domain
447 of the hierarchy which has it enabled, processes are always only on
452 processes and anonymous resource consumption which can't be associated
530 Let's also say U0 wants to write the PID of a process which is
539 namespace of the process which is attempting the migration.  If either
567 directory and it is possible to create children cgroups which collide
575 start or end with terms which are often used in categorizing workloads
595 weight against the sum.  As only children which can make use of the
619 Limits are in the range [0, max] and defaults to "max", which is noop.
635 soft boundaries.  Protections can also be over-committed in which case
639 Protections are in the range [0, max] and defaults to 0, which is
658 Allocations are in the range [0, max] and defaults to 0, which is no
752   For example, a setting which is keyed by major:minor device numbers
778 - For events which are not very high frequency, an interface file
779   "events" should be created which lists event key value pairs.
791 	A read-write single value file which exists on non-root
794 	When read, it indicates the current type of the cgroup, which
799 	- "domain threaded" : A threaded domain cgroup which is
802 	- "domain invalid" : A cgroup which is in an invalid state.
806 	- "threaded" : A threaded cgroup which is a member of a
813 	A read-write new-line separated values file which exists on
816 	When read, it lists the PIDs of all processes which belong to
839 	A read-write new-line separated values file which exists on
842 	When read, it lists the TIDs of all threads which belong to
864 	A read-only space separated values file which exists on all
871 	A read-write space separated values file which exists on all
875 	which are enabled to control resource distribution from the
886 	A read-only flat-keyed file which exists on non-root cgroups.
920 		in dying state for some time undefined time (which can depend
927 		limits, which were active at the moment of cgroup deletion.
930 	A read-write single value file which exists on non-root cgroups.
967 base and it does not account for the frequency at which tasks are executed.
969 cpufreq governor about the minimum desired frequency which should always be
970 provided by a CPU, as well as the maximum desired frequency, which should not
1003 	A read-write single value file which exists on non-root
1009 	A read-write single value file which exists on non-root
1021 	A read-write two value file which exists on non-root cgroups.
1028 	which indicates that the group may consume upto $MAX in each
1033 	A read-only nested-key file which exists on non-root cgroups.
1039         A read-write single value file which exists on non-root cgroups.
1054         A read-write single value file which exists on non-root cgroups.
1092 All memory amounts are in bytes.  If a value which is not aligned to
1097 	A read-only single value file which exists on non-root
1104 	A read-write single value file which exists on non-root
1130 	A read-write single value file which exists on non-root
1153 	A read-write single value file which exists on non-root
1165 	A read-write single value file which exists on non-root
1186 	A read-write single value file which exists on non-root
1204 	A read-only flat-keyed file which exists on non-root cgroups.
1251 	A read-only flat-keyed file which exists on non-root cgroups.
1340 		Number of restored anonymous pages which have been detected as
1344 		Number of restored file pages which have been detected as an
1378 		Number of transparent hugepages which were allocated to satisfy
1383 		Number of transparent hugepages which were allocated to allow
1388 	A read-only nested-keyed file which exists on non-root cgroups.
1413 	A read-only single value file which exists on non-root
1420 	A read-write single value file which exists on non-root
1429 	during regular operation. Compare to memory.swap.max, which
1436 	A read-write single value file which exists on non-root
1443 	A read-only flat-keyed file which exists on non-root cgroups.
1468 	A read-only nested-key file which exists on non-root cgroups.
1489 more memory.  For example, a workload which writes data received from
1501 A memory area is charged to the cgroup which instantiated it and stays
1507 To which cgroup the area will be charged is in-deterministic; however,
1508 over time, the memory area is likely to end up in a cgroup which has
1511 If a cgroup sweeps a considerable amount of memory which is expected
1555 	model based controller (CONFIG_BLK_CGROUP_IOCOST) which
1595 	devices which show wide temporary behavior changes - e.g. a
1596 	ssd which accepts writes at the line speed for a while and
1610 	controller (CONFIG_BLK_CGROUP_IOCOST) which currently
1648 	A read-write flat-keyed file which exists on non-root cgroups.
1668 	A read-write nested-keyed file which exists on non-root
1707 	A read-only nested-key file which exists on non-root cgroups.
1725 maintained for and the io controller defines the io domain which
1736 which affects how cgroup ownership is tracked.  Memory is tracked per
1742 which are associated with different cgroups than the one the inode is
1759 The sysctl knobs which affect writeback behavior are applied to cgroup
1913 The number of tasks in a cgroup can be exhausted in ways which other
1926 	A read-write single value file which exists on non-root
1932 	A read-only single value file which exists on all cgroups.
1965 	A read-write multiple values file which exists on non-root
1987 	A read-only multiple values file which exists on all
2004 	A read-write multiple values file which exists on non-root
2027 	A read-only multiple values file which exists on all
2043 	A read-write single value file which exists on non-root
2131 structure, which describes the device access attempt: access type
2197 	A read-only flat-keyed file which exists on non-root cgroups.
2302 The 'cgroupns root' for a cgroup namespace is the cgroup in which the
2425 selective disabling of cgroup writeback support which is helpful when
2464 type controllers such as freezer which can be useful in all
2472 In practice, these issues heavily limited which controllers could be
2485 There was no limit on how many hierarchies there might be, which meant
2488 in length, which made it highly awkward to manipulate and led to
2489 addition of controllers which existed only to identify membership,
2490 which in turn exacerbated the original problem of proliferating number
2499 In most use cases, putting controllers on hierarchies which are
2521 the application which owns the target process.
2523 cgroup v1 had an ambiguously defined delegation model which got abused
2539 cgroup controllers implemented a number of knobs which would never be
2542 knobs which were not properly abstracted or refined and directly
2556 cgroup v1 allowed threads to be in any cgroups which created an
2568 wasn't obvious or universal, and there were various other knobs which
2575 always added an extra layer of nesting which wouldn't be necessary
2582 knobs to tailor the behavior to specific workloads which would have
2590 This clearly is a problem which needs to be addressed from cgroup core
2645 effective low, which makes delegation of subtrees possible. It also