Lines Matching +full:sub +full:- +full:controllers
1 .. _cgroup-v2:
11 conventions of cgroup v2. It describes all userland-visible aspects
14 v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgroup-v1>`.
19 1-1. Terminology
20 1-2. What is cgroup?
22 2-1. Mounting
23 2-2. Organizing Processes and Threads
24 2-2-1. Processes
25 2-2-2. Threads
26 2-3. [Un]populated Notification
27 2-4. Controlling Controllers
28 2-4-1. Enabling and Disabling
29 2-4-2. Top-down Constraint
30 2-4-3. No Internal Process Constraint
31 2-5. Delegation
32 2-5-1. Model of Delegation
33 2-5-2. Delegation Containment
34 2-6. Guidelines
35 2-6-1. Organize Once and Control
36 2-6-2. Avoid Name Collisions
38 3-1. Weights
39 3-2. Limits
40 3-3. Protections
41 3-4. Allocations
43 4-1. Format
44 4-2. Conventions
45 4-3. Core Interface Files
46 5. Controllers
47 5-1. CPU
48 5-1-1. CPU Interface Files
49 5-2. Memory
50 5-2-1. Memory Interface Files
51 5-2-2. Usage Guidelines
52 5-2-3. Memory Ownership
53 5-3. IO
54 5-3-1. IO Interface Files
55 5-3-2. Writeback
56 5-3-3. IO Latency
57 5-3-3-1. How IO Latency Throttling Works
58 5-3-3-2. IO Latency Interface Files
59 5-3-4. IO Priority
60 5-4. PID
61 5-4-1. PID Interface Files
62 5-5. Cpuset
63 5.5-1. Cpuset Interface Files
64 5-6. Device
65 5-7. RDMA
66 5-7-1. RDMA Interface Files
67 5-8. HugeTLB
68 5.8-1. HugeTLB Interface Files
69 5-9. Misc
70 5.9-1 Miscellaneous cgroup Interface Files
71 5.9-2 Migration and Ownership
72 5-10. Others
73 5-10-1. perf_event
74 5-N. Non-normative information
75 5-N-1. CPU controller root cgroup process behaviour
76 5-N-2. IO controller root cgroup process behaviour
78 6-1. Basics
79 6-2. The Root and Views
80 6-3. Migration and setns(2)
81 6-4. Interaction with Other Namespaces
83 P-1. Filesystem Support for Writeback
86 R-1. Multiple Hierarchies
87 R-2. Thread Granularity
88 R-3. Competition Between Inner Nodes and Threads
89 R-4. Other Interface Issues
90 R-5. Controller Issues and Remedies
91 R-5-1. Memory
98 -----------
102 qualifier as in "cgroup controllers". When explicitly referring to
107 ---------------
113 cgroup is largely composed of two parts - the core and controllers.
117 although there are utility controllers which serve purposes other than
127 Following certain structural constraints, controllers may be enabled or
129 hierarchical - if a controller is enabled on a cgroup, it affects all
131 sub-hierarchy of the cgroup. When a controller is enabled on a nested
141 --------
146 # mount -t cgroup2 none $MOUNT_POINT
149 controllers which support v2 and are not bound to a v1 hierarchy are
151 Controllers which are not in active use in the v2 hierarchy can be
156 is no longer referenced in its current hierarchy. Because per-cgroup
157 controller states are destroyed asynchronously and controllers may
163 to inter-controller dependencies, other controllers may need to be
167 controllers dynamically between the v2 and other hierarchies is
170 controllers after system boot.
173 automount the v1 cgroup filesystem and so hijack all controllers
176 disabling controllers in v1 and make them always available in v2.
184 ignored on non-init namespace mounts. Please refer to the
192 controllers, and then seeding it with CLONE_INTO_CGROUP is
201 option is ignored on non-init namespace mounts.
209 behavior but is a mount-option to avoid regressing setups
215 --------------------------------
221 A child cgroup can be created by creating a sub-directory::
226 structure. Each cgroup has a read-writable interface file
228 belong to the cgroup one-per-line. The PIDs are not ordered and the
259 0::/test-cgroup/test-cgroup-nested
266 0::/test-cgroup/test-cgroup-nested (deleted)
272 cgroup v2 supports thread granularity for a subset of controllers to
280 Controllers which support thread mode are called threaded controllers.
281 The ones which don't are called domain controllers.
292 constraint - threaded controllers can be enabled on non-leaf cgroups
316 - As the cgroup will join the parent's resource domain. The parent
319 - When the parent is an unthreaded domain, it must not have any domain
320 controllers enabled or populated domain children. The root is
323 Topology-wise, a cgroup can be in an invalid state. Please consider
326 A (threaded domain) - B (threaded) - C (domain, just created)
335 cgroup becomes threaded or threaded controllers are enabled in the
341 threads in the cgroup. Except that the operations are per-thread
342 instead of per-process, "cgroup.threads" has the same format and
356 Only threaded controllers can be enabled in a threaded subtree. When
364 between threads in a non-leaf cgroup and its child cgroups. Each
369 --------------------------
371 Each non-root cgroup has a "cgroup.events" file which contains
372 "populated" field indicating whether the cgroup's sub-hierarchy has
376 example, to start a clean-up operation after all processes of a given
377 sub-hierarchy have exited. The populated state updates and
378 notifications are recursive. Consider the following sub-hierarchy
382 A(4) - B(0) - C(1)
391 Controlling Controllers
392 -----------------------
397 Each cgroup has a "cgroup.controllers" file which lists all
398 controllers available for the cgroup to enable::
400 # cat cgroup.controllers
403 No controller is enabled by default. Controllers can be enabled and
406 # echo "+cpu +memory -io" > cgroup.subtree_control
408 Only controllers which are listed in "cgroup.controllers" can be
415 Consider the following sub-hierarchy. The enabled controllers are
418 A(cpu,memory) - B(memory) - C()
432 controller interface files - anything which doesn't start with
436 Top-down Constraint
439 Resources are distributed top-down and a cgroup can further distribute
441 parent. This means that all non-root "cgroup.subtree_control" files
442 can only contain controllers which are enabled in the parent's
451 Non-root cgroups can distribute domain resources to their children
454 controllers enabled in their "cgroup.subtree_control" files.
464 controllers. How resource consumption in the root cgroup is governed
466 refer to the Non-normative information section in the Controllers
474 children before enabling controllers in its "cgroup.subtree_control"
479 ----------
499 delegated, the user can build sub-hierarchy under the directory,
502 of all resource controllers are hierarchical and regardless of what
503 happens in the delegated sub-hierarchy, nothing can escape the
507 cgroups in or nesting depth of a delegated sub-hierarchy; however,
514 A delegated sub-hierarchy is contained in the sense that processes
515 can't be moved into or out of the sub-hierarchy by the delegatee.
518 requiring the following conditions for a process with a non-root euid
522 - The writer must have write access to the "cgroup.procs" file.
524 - The writer must have write access to the "cgroup.procs" file of the
528 processes around freely in the delegated sub-hierarchy it can't pull
529 in from or push out to outside the sub-hierarchy.
535 ~~~~~~~~~~~~~ - C0 - C00
538 ~~~~~~~~~~~~~ - C1 - C10
545 will be denied with -EACCES.
550 is not reachable, the migration is rejected with -ENOENT.
554 ----------
562 inherent trade-offs between migration and various hot paths in terms
568 resource structure once on start-up. Dynamic adjustments to resource
595 cgroup controllers implement several resource distribution schemes
601 -------
607 work-conserving. Due to the dynamic nature, this model is usually
622 .. _cgroupv2-limits-distributor:
625 ------
628 Limits can be over-committed - the sum of the limits of children can
633 As limits can be over-committed, all configuration combinations are
640 .. _cgroupv2-protections-distributor:
643 -----------
648 soft boundaries. Protections can also be over-committed in which case
655 As protections can be over-committed, all configuration combinations
659 "memory.low" implements best-effort memory protection and is an
664 -----------
667 resource. Allocations can't be over-committed - the sum of the
674 As allocations can't be over-committed, some configuration
679 "cpu.rt.max" hard-allocates realtime slices and is an example of this
687 ------
692 New-line separated values
700 (when read-only or multiple values can be written at once)
717 reading; however, controllers may allow omitting later fields or
721 can be written at a time. For nested keyed files, the sub key pairs
726 -----------
728 - Settings for a single feature should be contained in a single file.
730 - The root cgroup should be exempt from resource control and thus
733 - The default time unit is microseconds. If a different unit is ever
736 - A parts-per quantity should use a percentage decimal with at least
737 two digit fractional part - e.g. 13.40.
739 - If a controller implements weight based resource distribution, its
745 - If a controller implements an absolute resource guarantee and/or
754 - If a setting has a configurable default value and keyed specific
768 # cat cgroup-example-interface-file
774 # echo 125 > cgroup-example-interface-file
778 # echo "default 125" > cgroup-example-interface-file
782 # echo "8:16 170" > cgroup-example-interface-file
786 # echo "8:0 default" > cgroup-example-interface-file
787 # cat cgroup-example-interface-file
791 - For events which are not very high frequency, an interface file
798 --------------------
803 A read-write single value file which exists on non-root
809 - "domain" : A normal valid domain cgroup.
811 - "domain threaded" : A threaded domain cgroup which is
814 - "domain invalid" : A cgroup which is in an invalid state.
815 It can't be populated or have controllers enabled. It may
818 - "threaded" : A threaded cgroup which is a member of a
825 A read-write new-line separated values file which exists on
829 the cgroup one-per-line. The PIDs are not ordered and the
838 - It must have write access to the "cgroup.procs" file.
840 - It must have write access to the "cgroup.procs" file of the
843 When delegating a sub-hierarchy, write access to this file
851 A read-write new-line separated values file which exists on
855 the cgroup one-per-line. The TIDs are not ordered and the
864 - It must have write access to the "cgroup.threads" file.
866 - The cgroup that the thread is currently in must be in the
869 - It must have write access to the "cgroup.procs" file of the
872 When delegating a sub-hierarchy, write access to this file
875 cgroup.controllers
876 A read-only space separated values file which exists on all
879 It shows space separated list of all controllers available to
880 the cgroup. The controllers are not ordered.
883 A read-write space separated values file which exists on all
886 When read, it shows space separated list of the controllers
890 Space separated list of controllers prefixed with '+' or '-'
891 can be written to enable or disable controllers. A controller
892 name prefixed with '+' enables the controller and '-'
898 A read-only flat-keyed file which exists on non-root cgroups.
910 A read-write single value files. The default is "max".
917 A read-write single value files. The default is "max".
924 A read-only flat-keyed file with the following entries:
942 A read-write single value file which exists on non-root cgroups.
965 create new sub-cgroups.
968 A write-only single value file which exists in non-root cgroups.
980 the whole thread-group.
983 A read-write single value file that allowed values are "0" and "1".
987 Writing "1" to the file will re-enable the cgroup PSI accounting.
995 This may cause non-negligible overhead for some workloads when under
997 be used to disable PSI accounting in the non-leaf cgroups.
1000 A read-write nested-keyed file.
1005 Controllers chapter
1008 .. _cgroup-v2-cpu:
1011 ---
1013 The "cpu" controllers regulates distribution of CPU cycles. This
1039 A read-only flat-keyed file.
1044 - usage_usec
1045 - user_usec
1046 - system_usec
1050 - nr_periods
1051 - nr_throttled
1052 - throttled_usec
1053 - nr_bursts
1054 - burst_usec
1057 A read-write single value file which exists on non-root
1063 A read-write single value file which exists on non-root
1066 The nice value is in the range [-20, 19].
1075 A read-write two value file which exists on non-root cgroups.
1087 A read-write single value file which exists on non-root
1093 A read-write nested-keyed file.
1099 A read-write single value file which exists on non-root cgroups.
1114 A read-write single value file which exists on non-root cgroups.
1127 ------
1135 While not completely water-tight, all major memory usages by a given
1140 - Userland memory - page cache and anonymous memory.
1142 - Kernel data structures such as dentries and inodes.
1144 - TCP socket buffers.
1157 A read-only single value file which exists on non-root
1164 A read-write single value file which exists on non-root
1190 A read-write single value file which exists on non-root
1193 Best-effort memory protection. If the memory usage of a
1213 A read-write single value file which exists on non-root
1227 A read-write single value file which exists on non-root
1236 In default configuration regular 0-order allocations always
1241 as -ENOMEM or silently ignore in cases like disk readahead.
1244 A write-only nested-keyed file which exists for all cgroups.
1262 specified amount, -EAGAIN is returned.
1272 A read-only single value file which exists on non-root
1279 A read-write single value file which exists on non-root
1289 Tasks with the OOM protection (oom_score_adj set to -1000)
1297 A read-only flat-keyed file which exists on non-root cgroups.
1311 boundary is over-committed.
1331 considered as an option, e.g. for failed high-order
1347 A read-only flat-keyed file which exists on non-root cgroups.
1350 types of memory, type-specific details, and other information
1359 If the entry has no per-node counter (or not show in the
1360 memory.numa_stat). We use 'npn' (non-per-node) as the tag
1388 Amount of memory used for storing per-cpu kernel
1398 Amount of cached filesystem data that is swap-backed,
1435 Amount of memory, swap-backed and filesystem-backed,
1441 the value for the foo counter, since the foo counter is type-based, not
1442 list-based.
1453 Amount of memory used for storing in-kernel data
1536 A read-only nested-keyed file which exists on non-root cgroups.
1539 types of memory, type-specific details, and other information
1561 A read-only single value file which exists on non-root
1568 A read-write single value file which exists on non-root
1573 allow userspace to implement custom out-of-memory procedures.
1584 A read-only single value file which exists on non-root
1591 A read-write single value file which exists on non-root
1598 A read-only flat-keyed file which exists on non-root cgroups.
1614 because of running out of swap system-wide or max
1623 A read-only single value file which exists on non-root
1630 A read-write single value file which exists on non-root
1638 A read-only nested-keyed file.
1648 Over-committing on high limit (sum of high limits > available memory)
1662 pressure - how much the workload is being impacted due to lack of
1663 memory - is necessary to determine whether a workload needs more
1677 To which cgroup the area will be charged is in-deterministic; however,
1688 --
1693 only if cfq-iosched is in use and neither scheme is available for
1694 blk-mq devices.
1701 A read-only nested-keyed file.
1721 A read-write nested-keyed file which exists only on the root
1733 enable Weight-based control enable
1765 devices which show wide temporary behavior changes - e.g. a
1776 A read-write nested-keyed file which exists only on the root
1789 model The cost model in use - "linear"
1815 generate device-specific coefficients.
1818 A read-write flat-keyed file which exists on non-root cgroups.
1838 A read-write nested-keyed file which exists on non-root
1852 When writing, any number of nested key-value pairs can be
1877 A read-only nested-keyed file.
1896 writes out dirty pages for the memory domain. Both system-wide and
1897 per-cgroup dirty memory states are examined and the more restrictive
1935 memory controller and system-wide clean memory.
1968 your real setting, setting at 10-15% higher than the value in io.stat.
1978 - Queue depth throttling. This is the number of outstanding IO's a group is
1982 - Artificial delay induction. There are certain types of IO that cannot be
2000 This takes a similar format as the other controllers.
2029 no-change
2032 promote-to-rt
2033 For requests that have a non-RT I/O priority class, change it into RT.
2037 restrict-to-be
2047 none-to-rt
2048 Deprecated. Just an alias for promote-to-rt.
2052 +----------------+---+
2053 | no-change | 0 |
2054 +----------------+---+
2055 | rt-to-be | 2 |
2056 +----------------+---+
2057 | all-to-idle | 3 |
2058 +----------------+---+
2062 +-------------------------------+---+
2064 +-------------------------------+---+
2065 | IOPRIO_CLASS_RT (real-time) | 1 |
2066 +-------------------------------+---+
2068 +-------------------------------+---+
2070 +-------------------------------+---+
2074 - If I/O priority class policy is promote-to-rt, change the request I/O
2077 - If I/O priorityt class is not promote-to-rt, translate the I/O priority
2083 ---
2090 controllers cannot prevent, thus warranting its own controller. For
2102 A read-write single value file which exists on non-root
2108 A read-only single value file which exists on all cgroups.
2118 through fork() or clone(). These will return -EAGAIN if the creation
2123 ------
2130 memory placement to reduce cross-node memory access and contention
2141 A read-write multiple values file which exists on non-root
2142 cpuset-enabled cgroups.
2149 The CPU numbers are comma-separated numbers or ranges.
2153 0-4,6,8-10
2156 setting as the nearest cgroup ancestor with a non-empty
2163 A read-only multiple values file which exists on all
2164 cpuset-enabled cgroups.
2180 A read-write multiple values file which exists on non-root
2181 cpuset-enabled cgroups.
2188 The memory node numbers are comma-separated numbers or ranges.
2192 0-1,3
2195 setting as the nearest cgroup ancestor with a non-empty
2202 Setting a non-empty value to "cpuset.mems" causes memory of
2214 A read-only multiple values file which exists on all
2215 cpuset-enabled cgroups.
2230 A read-write single value file which exists on non-root
2231 cpuset-enabled cgroups. This flag is owned by the parent cgroup
2237 "member" Non-root member of a partition
2243 cannot be changed. All other non-root cgroups start out as
2263 two possible states - valid or invalid. An invalid partition
2274 "member" Non-root member of a partition
2306 A valid non-root parent partition may distribute out all its CPUs
2326 -----------------
2337 on the return value the attempt will succeed or fail with -EPERM.
2342 If the program returns 0, the attempt fails with -EPERM, otherwise it
2350 ----
2359 A readwrite nested-keyed file that exists for all the cgroups
2380 A read-only file that describes current resource usage.
2389 -------
2406 A read-only flat-keyed file which exists on non-root cgroups.
2419 use hugetlb pages are included. The per-node values are in bytes.
2422 ----
2444 A read-only flat-keyed file shown only in the root cgroup. It shows
2453 A read-only flat-keyed file shown in the all cgroups. It shows
2461 A read-write flat-keyed file shown in the non root cgroups. Allowed
2480 A read-only flat-keyed file which exists on non-root cgroups. The
2498 ------
2509 Non-normative information
2510 -------------------------
2526 appropriately so the neutral - nice 0 - value is 100 instead of 1024).
2542 ------
2561 The path '/batchjobs/container_id1' can be considered as system-data
2566 # ls -l /proc/self/ns/cgroup
2567 lrwxrwxrwx 1 root root 0 2014-07-15 10:37 /proc/self/ns/cgroup -> cgroup:[4026531835]
2573 # ls -l /proc/self/ns/cgroup
2574 lrwxrwxrwx 1 root root 0 2014-07-15 10:35 /proc/self/ns/cgroup -> cgroup:[4026532183]
2578 When some thread from a multi-threaded process unshares its cgroup
2590 ------------------
2601 # ~/unshare -c # unshare cgroupns in some cgroup
2609 Each process gets its namespace-specific view of "/proc/$PID/cgroup"
2640 ----------------------
2669 ---------------------------------
2672 running inside a non-init cgroup namespace::
2674 # mount -t cgroup2 none $MOUNT_POINT
2681 the view of cgroup hierarchy by namespace-private cgroupfs mount
2690 controllers are not covered.
2694 --------------------------------
2697 address_space_operations->writepage[s]() to annotate bio's using the
2714 super_block by setting SB_I_CGROUPWB in ->s_iflags. This allows for
2731 - Multiple hierarchies including named ones are not supported.
2733 - All v1 mount options are not supported.
2735 - The "tasks" file is removed and "cgroup.procs" is not sorted.
2737 - "cgroup.clone_children" is removed.
2739 - /proc/cgroups is meaningless for v2. Use "cgroup.controllers" file
2747 --------------------
2750 hierarchy could host any number of controllers. While this seemed to
2754 type controllers such as freezer which can be useful in all
2756 the fact that controllers couldn't be moved to another hierarchy once
2757 hierarchies were populated. Another issue was that all controllers
2762 In practice, these issues heavily limited which controllers could be
2765 as the cpu and cpuacct controllers, made sense to be put on the same
2773 used in general and what controllers was able to do.
2779 addition of controllers which existed only to identify membership,
2784 topologies of hierarchies other controllers might be on, each
2785 controller had to assume that all other controllers were attached to
2787 least very cumbersome, for controllers to cooperate with each other.
2789 In most use cases, putting controllers on hierarchies which are
2794 controllers. For example, a given configuration might not care about
2800 ------------------
2803 This didn't make sense for some controllers and those controllers
2808 Generally, in-process knowledge is available only to the process
2809 itself; thus, unlike service-level organization of processes,
2816 sub-hierarchies and control resource distributions along them. This
2817 effectively raised cgroup to the status of a syscall-like API exposed
2827 that the process would actually be operating on its own sub-hierarchy.
2829 cgroup controllers implemented a number of knobs which would never be
2831 system-management pseudo filesystem. cgroup ended up with interface
2834 individual applications through the ill-defined delegation mechanism
2844 -------------------------------------------
2850 settle it. Different controllers did different things.
2855 cycles and the number of internal threads fluctuated - the ratios
2871 clearly defined. There were attempts to add ad-hoc behaviors and
2875 Multiple controllers struggled with internal tasks and came up with
2885 ----------------------
2889 was how an empty cgroup was notified - a userland helper binary was
2892 to in-kernel event delivery filtering mechanism further complicating
2896 controllers completely ignoring hierarchical organization and treating
2898 cgroup. Some controllers exposed a large amount of inconsistent
2901 There also was no consistency across controllers. When a new cgroup
2902 was created, some controllers defaulted to not imposing extra
2910 controllers so that they expose minimal and consistent interfaces.
2914 ------------------------------
2921 global reclaim prefers is opt-in, rather than opt-out. The costs for
2931 becomes self-defeating.
2933 The memory.low boundary on the other hand is a top-down allocated
2971 new limit is met - or the task writing to memory.max is killed.
2980 groups can sabotage swapping by other means - such as referencing its
2981 anonymous memory in a tight loop - and an admin can not assume full
2986 that cgroup controllers should account and limit specific physical