diff options
Diffstat (limited to 'Documentation/admin-guide/cgroup-v2.rst')
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 287 |
1 files changed, 237 insertions, 50 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 315ede811c9d..7f5b59d95fce 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -15,6 +15,9 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou .. CONTENTS + [Whenever any new section is added to this document, please also add + an entry here.] + 1. Introduction 1-1. Terminology 1-2. What is cgroup? @@ -25,9 +28,10 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou 2-2-2. Threads 2-3. [Un]populated Notification 2-4. Controlling Controllers - 2-4-1. Enabling and Disabling - 2-4-2. Top-down Constraint - 2-4-3. No Internal Process Constraint + 2-4-1. Availability + 2-4-2. Enabling and Disabling + 2-4-3. Top-down Constraint + 2-4-4. No Internal Process Constraint 2-5. Delegation 2-5-1. Model of Delegation 2-5-2. Delegation Containment @@ -49,7 +53,8 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou 5-2. Memory 5-2-1. Memory Interface Files 5-2-2. Usage Guidelines - 5-2-3. Memory Ownership + 5-2-3. Reclaim Protection + 5-2-4. Memory Ownership 5-3. IO 5-3-1. IO Interface Files 5-3-2. Writeback @@ -61,16 +66,18 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou 5-4-1. PID Interface Files 5-5. Cpuset 5.5-1. Cpuset Interface Files - 5-6. Device + 5-6. Device controller 5-7. RDMA 5-7-1. RDMA Interface Files - 5-8. HugeTLB - 5.8-1. HugeTLB Interface Files - 5-9. Misc - 5.9-1 Miscellaneous cgroup Interface Files - 5.9-2 Migration and Ownership - 5-10. Others - 5-10-1. perf_event + 5-8. DMEM + 5-8-1. DMEM Interface Files + 5-9. HugeTLB + 5.9-1. HugeTLB Interface Files + 5-10. Misc + 5.10-1 Misc Interface Files + 5.10-2 Migration and Ownership + 5-11. Others + 5-11-1. perf_event 5-N. Non-normative information 5-N-1. CPU controller root cgroup process behaviour 5-N-2. IO controller root cgroup process behaviour @@ -434,6 +441,15 @@ both cgroups. Controlling Controllers ----------------------- +Availability +~~~~~~~~~~~~ + +A controller is available in a cgroup when it is supported by the kernel (i.e., +compiled in, not disabled and not attached to a v1 hierarchy) and listed in the +"cgroup.controllers" file. Availability means the controller's interface files +are exposed in the cgroup’s directory, allowing the distribution of the target +resource to be observed or controlled within that cgroup. + Enabling and Disabling ~~~~~~~~~~~~~~~~~~~~~~ @@ -991,6 +1007,24 @@ All cgroup core files are prefixed with "cgroup." Total number of dying cgroup subsystems (e.g. memory cgroup) at and beneath the current cgroup. + cgroup.stat.local + A read-only flat-keyed file which exists in non-root cgroups. + The following entry is defined: + + frozen_usec + Cumulative time that this cgroup has spent between freezing and + thawing, regardless of whether by self or ancestor groups. + NB: (not) reaching "frozen" state is not accounted here. + + Using the following ASCII representation of a cgroup's freezer + state, :: + + 1 _____ + frozen 0 __/ \__ + ab cd + + the duration being measured is the span between a and c. + cgroup.freeze A read-write single value file which exists on non-root cgroups. Allowed values are "0" and "1". The default is "0". @@ -1075,33 +1109,53 @@ cpufreq governor about the minimum desired frequency which should always be provided by a CPU, as well as the maximum desired frequency, which should not be exceeded by a CPU. -WARNING: cgroup2 doesn't yet support control of realtime processes. For -a kernel built with the CONFIG_RT_GROUP_SCHED option enabled for group -scheduling of realtime processes, the cpu controller can only be enabled -when all RT processes are in the root cgroup. This limitation does -not apply if CONFIG_RT_GROUP_SCHED is disabled. Be aware that system -management software may already have placed RT processes into nonroot -cgroups during the system boot process, and these processes may need -to be moved to the root cgroup before the cpu controller can be enabled -with a CONFIG_RT_GROUP_SCHED enabled kernel. +WARNING: cgroup2 cpu controller doesn't yet support the (bandwidth) control of +realtime processes. For a kernel built with the CONFIG_RT_GROUP_SCHED option +enabled for group scheduling of realtime processes, the cpu controller can only +be enabled when all RT processes are in the root cgroup. Be aware that system +management software may already have placed RT processes into non-root cgroups +during the system boot process, and these processes may need to be moved to the +root cgroup before the cpu controller can be enabled with a +CONFIG_RT_GROUP_SCHED enabled kernel. + +With CONFIG_RT_GROUP_SCHED disabled, this limitation does not apply and some of +the interface files either affect realtime processes or account for them. See +the following section for details. Only the cpu controller is affected by +CONFIG_RT_GROUP_SCHED. Other controllers can be used for the resource control of +realtime processes irrespective of CONFIG_RT_GROUP_SCHED. CPU Interface Files ~~~~~~~~~~~~~~~~~~~ -All time durations are in microseconds. +The interaction of a process with the cpu controller depends on its scheduling +policy and the underlying scheduler. From the point of view of the cpu controller, +processes can be categorized as follows: + +* Processes under the fair-class scheduler +* Processes under a BPF scheduler with the ``cgroup_set_weight`` callback +* Everything else: ``SCHED_{FIFO,RR,DEADLINE}`` and processes under a BPF scheduler + without the ``cgroup_set_weight`` callback + +For details on when a process is under the fair-class scheduler or a BPF scheduler, +check out :ref:`Documentation/scheduler/sched-ext.rst <sched-ext>`. + +For each of the following interface files, the above categories +will be referred to. All time durations are in microseconds. cpu.stat A read-only flat-keyed file. This file exists whether the controller is enabled or not. - It always reports the following three stats: + It always reports the following three stats, which account for all the + processes in the cgroup: - usage_usec - user_usec - system_usec - and the following five when the controller is enabled: + and the following five when the controller is enabled, which account for + only the processes under the fair-class scheduler: - nr_periods - nr_throttled @@ -1119,6 +1173,10 @@ All time durations are in microseconds. If the cgroup has been configured to be SCHED_IDLE (cpu.idle = 1), then the weight will show as a 0. + This file affects only processes under the fair-class scheduler and a BPF + scheduler with the ``cgroup_set_weight`` callback depending on what the + callback actually does. + cpu.weight.nice A read-write single value file which exists on non-root cgroups. The default is "0". @@ -1131,6 +1189,10 @@ All time durations are in microseconds. granularity is coarser for the nice values, the read value is the closest approximation of the current weight. + This file affects only processes under the fair-class scheduler and a BPF + scheduler with the ``cgroup_set_weight`` callback depending on what the + callback actually does. + cpu.max A read-write two value file which exists on non-root cgroups. The default is "max 100000". @@ -1143,43 +1205,55 @@ All time durations are in microseconds. $PERIOD duration. "max" for $MAX indicates no limit. If only one number is written, $MAX is updated. + This file affects only processes under the fair-class scheduler. + cpu.max.burst A read-write single value file which exists on non-root cgroups. The default is "0". The burst in the range [0, $MAX]. + This file affects only processes under the fair-class scheduler. + cpu.pressure A read-write nested-keyed file. Shows pressure stall information for CPU. See :ref:`Documentation/accounting/psi.rst <psi>` for details. + This file accounts for all the processes in the cgroup. + cpu.uclamp.min - A read-write single value file which exists on non-root cgroups. - The default is "0", i.e. no utilization boosting. + A read-write single value file which exists on non-root cgroups. + The default is "0", i.e. no utilization boosting. + + The requested minimum utilization (protection) as a percentage + rational number, e.g. 12.34 for 12.34%. - The requested minimum utilization (protection) as a percentage - rational number, e.g. 12.34 for 12.34%. + This interface allows reading and setting minimum utilization clamp + values similar to the sched_setattr(2). This minimum utilization + value is used to clamp the task specific minimum utilization clamp, + including those of realtime processes. - This interface allows reading and setting minimum utilization clamp - values similar to the sched_setattr(2). This minimum utilization - value is used to clamp the task specific minimum utilization clamp. + The requested minimum utilization (protection) is always capped by + the current value for the maximum utilization (limit), i.e. + `cpu.uclamp.max`. - The requested minimum utilization (protection) is always capped by - the current value for the maximum utilization (limit), i.e. - `cpu.uclamp.max`. + This file affects all the processes in the cgroup. cpu.uclamp.max - A read-write single value file which exists on non-root cgroups. - The default is "max". i.e. no utilization capping + A read-write single value file which exists on non-root cgroups. + The default is "max". i.e. no utilization capping + + The requested maximum utilization (limit) as a percentage rational + number, e.g. 98.76 for 98.76%. - The requested maximum utilization (limit) as a percentage rational - number, e.g. 98.76 for 98.76%. + This interface allows reading and setting maximum utilization clamp + values similar to the sched_setattr(2). This maximum utilization + value is used to clamp the task specific maximum utilization clamp, + including those of realtime processes. - This interface allows reading and setting maximum utilization clamp - values similar to the sched_setattr(2). This maximum utilization - value is used to clamp the task specific maximum utilization clamp. + This file affects all the processes in the cgroup. cpu.idle A read-write single value file which exists on non-root cgroups. @@ -1191,7 +1265,7 @@ All time durations are in microseconds. own relative priorities, but the cgroup itself will be treated as very low priority relative to its peers. - + This file affects only processes under the fair-class scheduler. Memory ------ @@ -1244,7 +1318,7 @@ PAGE_SIZE multiple when read back. smaller overages. Effective min boundary is limited by memory.min values of - all ancestor cgroups. If there is memory.min overcommitment + ancestor cgroups. If there is memory.min overcommitment (child cgroup or cgroups are requiring more protected memory than parent will allow), then each child cgroup will get the part of parent's protection proportional to its @@ -1253,9 +1327,6 @@ PAGE_SIZE multiple when read back. Putting more memory than generally available under this protection is discouraged and may lead to constant OOMs. - If a memory cgroup is not populated with processes, - its memory.min is ignored. - memory.low A read-write single value file which exists on non-root cgroups. The default is "0". @@ -1270,7 +1341,7 @@ PAGE_SIZE multiple when read back. smaller overages. Effective low boundary is limited by memory.low values of - all ancestor cgroups. If there is memory.low overcommitment + ancestor cgroups. If there is memory.low overcommitment (child cgroup or cgroups are requiring more protected memory than parent will allow), then each child cgroup will get the part of parent's protection proportional to its @@ -1293,6 +1364,18 @@ PAGE_SIZE multiple when read back. monitors the limited cgroup to alleviate heavy reclaim pressure. + If memory.high is opened with O_NONBLOCK then the synchronous + reclaim is bypassed. This is useful for admin processes that + need to dynamically adjust the job's memory limits without + expending their own CPU resources on memory reclamation. The + job will trigger the reclaim and/or get throttled on its + next charge request. + + Please note that with O_NONBLOCK, there is a chance that the + target memory cgroup may take indefinite amount of time to + reduce usage below the limit due to delayed charge request or + busy-hitting its memory to slow down reclaim. + memory.max A read-write single value file which exists on non-root cgroups. The default is "max". @@ -1310,6 +1393,18 @@ PAGE_SIZE multiple when read back. Caller could retry them differently, return into userspace as -ENOMEM or silently ignore in cases like disk readahead. + If memory.max is opened with O_NONBLOCK, then the synchronous + reclaim and oom-kill are bypassed. This is useful for admin + processes that need to dynamically adjust the job's memory limits + without expending their own CPU resources on memory reclamation. + The job will trigger the reclaim and/or oom-kill on its next + charge request. + + Please note that with O_NONBLOCK, there is a chance that the + target memory cgroup may take indefinite amount of time to + reduce usage below the limit due to delayed charge request or + busy-hitting its memory to slow down reclaim. + memory.reclaim A write-only nested-keyed file which exists for all cgroups. @@ -1342,6 +1437,9 @@ The following nested keys are defined. same semantics as vm.swappiness applied to memcg reclaim with all the existing limitations and potential future extensions. + The valid range for swappiness is [0-200, max], setting + swappiness=max exclusively reclaims anonymous memory. + memory.peak A read-write single value file which exists on non-root cgroups. @@ -1415,6 +1513,10 @@ The following nested keys are defined. oom_group_kill The number of times a group OOM has occurred. + sock_throttled + The number of times network sockets associated with + this cgroup are throttled. + memory.events.local Similar to memory.events but the fields in the file are local to the cgroup i.e. not hierarchical. The file modified event @@ -1439,7 +1541,10 @@ The following nested keys are defined. anon Amount of memory used in anonymous mappings such as - brk(), sbrk(), and mmap(MAP_ANONYMOUS) + brk(), sbrk(), and mmap(MAP_ANONYMOUS). Note that + some kernel configurations might account complete larger + allocations (e.g., THP) if only some, but not all the + memory of such an allocation is mapped anymore. file Amount of memory used to cache filesystem data, @@ -1482,7 +1587,10 @@ The following nested keys are defined. Amount of application memory swapped out to zswap. file_mapped - Amount of cached filesystem data mapped with mmap() + Amount of cached filesystem data mapped with mmap(). Note + that some kernel configurations might account complete + larger allocations (e.g., THP) if only some, but not + not all the memory of such an allocation is mapped. file_dirty Amount of cached filesystem data that was modified but @@ -1554,6 +1662,12 @@ The following nested keys are defined. workingset_nodereclaim Number of times a shadow node has been reclaimed + pswpin (npn) + Number of pages swapped into memory + + pswpout (npn) + Number of pages swapped out of memory + pgscan (npn) Amount of scanned pages (in an inactive LRU list) @@ -1569,6 +1683,9 @@ The following nested keys are defined. pgscan_khugepaged (npn) Amount of scanned pages by khugepaged (in an inactive LRU list) + pgscan_proactive (npn) + Amount of scanned pages proactively (in an inactive LRU list) + pgsteal_kswapd (npn) Amount of reclaimed pages by kswapd @@ -1578,6 +1695,9 @@ The following nested keys are defined. pgsteal_khugepaged (npn) Amount of reclaimed pages by khugepaged + pgsteal_proactive (npn) + Amount of reclaimed pages proactively + pgfault (npn) Total number of page faults incurred @@ -1655,6 +1775,9 @@ The following nested keys are defined. pgdemote_khugepaged Number of pages demoted by khugepaged. + pgdemote_proactive + Number of pages demoted by proactively. + hugetlb Amount of memory used by hugetlb pages. This metric only shows up if hugetlb usage is accounted for in memory.current (i.e. @@ -1813,6 +1936,27 @@ memory - is necessary to determine whether a workload needs more memory; unfortunately, memory pressure monitoring mechanism isn't implemented yet. +Reclaim Protection +~~~~~~~~~~~~~~~~~~ + +The protection configured with "memory.low" or "memory.min" applies relatively +to the target of the reclaim (i.e. any of memory cgroup limits, proactive +memory.reclaim or global reclaim apparently located in the root cgroup). +The protection value configured for B applies unchanged to the reclaim +targeting A (i.e. caused by competition with the sibling E):: + + root - ... - A - B - C + \ ` D + ` E + +When the reclaim targets ancestors of A, the effective protection of B is +capped by the protection value configured for A (and any other intermediate +ancestors between A and the target). + +To express indifference about relative sibling protection, it is suggested to +use memory_recursiveprot. Configuring all descendants of a parent with finite +protection to "max" works but it may unnecessarily skew memory.events:low +field. Memory Ownership ~~~~~~~~~~~~~~~~ @@ -2626,6 +2770,49 @@ RDMA Interface Files mlx4_0 hca_handle=1 hca_object=20 ocrdma1 hca_handle=1 hca_object=23 +DMEM +---- + +The "dmem" controller regulates the distribution and accounting of +device memory regions. Because each memory region may have its own page size, +which does not have to be equal to the system page size, the units are always bytes. + +DMEM Interface Files +~~~~~~~~~~~~~~~~~~~~ + + dmem.max, dmem.min, dmem.low + A readwrite nested-keyed file that exists for all the cgroups + except root that describes current configured resource limit + for a region. + + An example for xe follows:: + + drm/0000:03:00.0/vram0 1073741824 + drm/0000:03:00.0/stolen max + + The semantics are the same as for the memory cgroup controller, and are + calculated in the same way. + + dmem.capacity + A read-only file that describes maximum region capacity. + It only exists on the root cgroup. Not all memory can be + allocated by cgroups, as the kernel reserves some for + internal use. + + An example for xe follows:: + + drm/0000:03:00.0/vram0 8514437120 + drm/0000:03:00.0/stolen 67108864 + + dmem.current + A read-only file that describes current resource usage. + It exists for all the cgroup except root. + + An example for xe follows:: + + drm/0000:03:00.0/vram0 12550144 + drm/0000:03:00.0/stolen 8650752 + HugeTLB ------- @@ -2949,7 +3136,7 @@ Filesystem Support for Writeback -------------------------------- A filesystem can support cgroup writeback by updating -address_space_operations->writepage[s]() to annotate bio's using the +address_space_operations->writepages() to annotate bio's using the following two functions. wbc_init_bio(@wbc, @bio) |