Lines Matching full:memory
2 Memory Resource Controller
12 The Memory Resource Controller has generically been referred to as the
13 memory controller in this document. Do not confuse memory controller
14 used here with the memory controller that is used in hardware.
17 When we mention a cgroup (cgroupfs's directory) with memory controller,
18 we call it "memory cgroup". When you see git-log and source code, you'll
22 Benefits and Purpose of the memory controller
25 The memory controller isolates the memory behaviour of a group of tasks
27 uses of the memory controller. The memory controller can be used to
30 Memory-hungry applications can be isolated and limited to a smaller
31 amount of memory.
32 b. Create a cgroup with a limited amount of memory; this can be used
34 c. Virtualization solutions can control the amount of memory they want
36 d. A CD/DVD burner could control the amount of memory used by the
38 of available memory.
48 - optionally, memory+swap usage can be accounted and limited.
53 - memory pressure notifier
57 Kernel memory support is a work in progress, and the current version provides
59 <cgroup-v1-memory-kernel-extension>`)
69 memory.usage_in_bytes show current usage for memory
71 memory.memsw.usage_in_bytes show current usage for memory+Swap
73 memory.limit_in_bytes set/show limit of memory usage
74 memory.memsw.limit_in_bytes set/show limit of memory+Swap usage
75 memory.failcnt show the number of memory usage hits limits
76 memory.memsw.failcnt show the number of memory+Swap hits limits
77 memory.max_usage_in_bytes show max memory usage recorded
78 memory.memsw.max_usage_in_bytes show max memory+Swap usage recorded
79 memory.soft_limit_in_bytes set/show soft limit of memory usage
83 memory.stat show various statistics
84 memory.use_hierarchy set/show hierarchical account enabled
87 memory.force_empty trigger forced page reclaim
88 memory.pressure_level set memory pressure notifications
91 memory.swappiness set/show swappiness parameter of vmscan
93 memory.move_charge_at_immigrate set/show controls of moving charges
96 memory.oom_control set/show oom controls.
99 memory.numa_stat show the number of memory usage per numa
101 memory.kmem.limit_in_bytes Deprecated knob to set and read the kernel
102 memory hard limit. Kernel hard limit is not
106 Kernel memory is still charged and reported
107 by memory.kmem.usage_in_bytes.
108 memory.kmem.usage_in_bytes show current kernel memory allocation
109 memory.kmem.failcnt show the number of kernel memory usage
111 memory.kmem.max_usage_in_bytes show max kernel memory usage recorded
113 memory.kmem.tcp.limit_in_bytes set/show hard limit for tcp buf memory
116 memory.kmem.tcp.usage_in_bytes show current tcp buf memory allocation
119 memory.kmem.tcp.failcnt show the number of tcp buf memory usage
123 memory.kmem.tcp.max_usage_in_bytes show max tcp buf memory usage recorded
131 The memory controller has a long history. A request for comments for the memory
133 there were several implementations for memory control. The goal of the
135 for memory control. The first RSS controller was posted by Balbir Singh [2]_
139 raised to allow user space handling of OOM. The current memory controller is
143 2. Memory Control
146 Memory is a unique resource in the sense that it is present in a limited
149 memory, the same physical memory needs to be reused to accomplish the task.
151 The memory controller implementation has been divided into phases. These
154 1. Memory controller
156 3. Kernel user memory accounting and slab control
159 The memory controller is the first controller developed.
165 page_counter tracks the current memory usage and limit of the group of
166 processes associated with the controller. Each cgroup has a memory controller
208 (*) page_cgroup structure is allocated at boot/memory-hotplug time.
244 the cgroup that brought it in -- this will happen on memory pressure).
246 But see :ref:`section 8.2 <cgroup-v1-memory-movable-charges>` when moving a
258 - memory.memsw.usage_in_bytes.
259 - memory.memsw.limit_in_bytes.
261 memsw means memory+swap. Usage of memory+swap is limited by
264 Example: Assume a system with 4G of swap. A task which allocates 6G of memory
265 (by mistake) under 2G memory limitation will use all swap.
270 2.4.1 why 'memory+swap' rather than swap
274 to move account from memory to swap...there is no change in usage of
275 memory+swap. In other words, when we want to limit the usage of swap without
276 affecting global LRU, memory+swap limit is better than just limiting swap from
279 2.4.2. What happens when a cgroup hits memory.memsw.limit_in_bytes
282 When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do swap-out
284 caches are dropped. But as mentioned above, global LRU can do swapout memory
285 from it for sanity of the system's memory management state. You can't forbid
293 to reclaim memory from the cgroup so as to make space for the new
296 cgroup. (See :ref:`10. OOM Control <cgroup-v1-memory-oom-control>` below.)
310 (See :ref:`oom_control <cgroup-v1-memory-oom-control>` section)
327 .. _cgroup-v1-memory-kernel-extension:
329 2.7 Kernel Memory Extension
332 With the Kernel memory extension, the Memory Controller is able to limit
333 the amount of kernel memory used by the system. Kernel memory is fundamentally
334 different than user memory, since it can't be swapped out, which makes it
337 Kernel memory accounting is enabled for all memory cgroups by default. But
338 it can be disabled system-wide by passing cgroup.memory=nokmem to the kernel
339 at boot time. In this case, kernel memory will not be accounted at all.
341 Kernel memory limits are not imposed for the root cgroup. Usage for the root
342 cgroup may or may not be accounted. The memory used is accumulated into
343 memory.kmem.usage_in_bytes, or in a separate counter when it makes sense.
349 Currently no soft limit is implemented for kernel memory. It is future work
352 2.7.1 Current Kernel Memory resources accounted
357 kernel memory, we prevent new processes from being created when the kernel
358 memory usage is too high.
368 sockets memory pressure:
369 some sockets protocols have memory pressure
370 thresholds. The Memory Controller allows them to be controlled individually
373 tcp memory pressure:
374 sockets memory pressure for the tcp protocol.
379 Because the "kmem" counter is fed to the main user counter, kernel memory can
380 never be limited completely independently of user memory. Say "U" is the user
386 accounting. Kernel memory is completely ignored.
389 Kernel memory is a subset of the user memory. This setup is useful in
390 deployments where the total amount of memory per-cgroup is overcommitted.
391 Overcommitting kernel memory limits is definitely not recommended, since the
392 box can still run out of non-reclaimable memory.
394 never greater than the total memory, and freely set U at the cost of his
398 In the current implementation, memory reclaim will NOT be triggered for
404 triggered for the cgroup for both kinds of memory. This setup gives the
405 admin a unified view of memory, and it is also useful for people who just
406 want to track kernel memory usage.
418 # mkdir /sys/fs/cgroup/memory
419 # mount -t cgroup none /sys/fs/cgroup/memory -o memory
423 # mkdir /sys/fs/cgroup/memory/0
424 # echo $$ > /sys/fs/cgroup/memory/0/tasks
426 4. Since now we're in the 0 cgroup, we can alter the memory limit::
428 # echo 4M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes
432 # cat /sys/fs/cgroup/memory/0/memory.limit_in_bytes
449 # cat /sys/fs/cgroup/memory/0/memory.usage_in_bytes
455 availability of memory on the system. The user is required to re-read
458 # echo 1 > memory.limit_in_bytes
459 # cat memory.limit_in_bytes
462 The memory.failcnt field gives the number of times that the cgroup limit was
465 The memory.stat file gives accounting information. Now, the number of
473 Performance test is also important. To see pure memory controller's overhead,
482 Trying usual test under memory controller is always helpful.
484 .. _cgroup-v1-memory-test-troubleshoot:
493 2. The user is using anonymous memory and swap is turned off or too low
499 <cgroup-v1-memory-oom-control>` (below) and seeing what happens will be
502 .. _cgroup-v1-memory-test-task-migration:
513 See :ref:`8. "Move charges at task migration" <cgroup-v1-memory-move-charges>`
519 <cgroup-v1-memory-test-troubleshoot>` and :ref:`4.2
520 <cgroup-v1-memory-test-task-migration>`, a cgroup might have some charge
536 memory.force_empty interface is provided to make cgroup's memory usage empty.
539 # echo 0 > memory.force_empty
546 memory pressure happens. If you want to avoid that, force_empty will be useful.
551 memory.stat file includes following statistics:
553 * per-memory cgroup local status
556 cache # of bytes of page cache memory.
557 rss # of bytes of anonymous and swap cache memory (includes
561 pgpgin # of charging events to the memory cgroup. The charging
564 pgpgout # of uncharging events to the memory cgroup. The uncharging
568 swapcached # of bytes of swap cached in memory
572 inactive_anon # of bytes of anonymous and swap cache memory on inactive
574 active_anon # of bytes of anonymous and swap cache memory on active
576 inactive_file # of bytes of file-backed memory and MADV_FREE anonymous
577 memory (LazyFree pages) on inactive LRU list.
578 active_file # of bytes of file-backed memory on active LRU list.
579 unevictable # of bytes of memory that cannot be reclaimed (mlocked etc).
582 * status considering hierarchy (see memory.use_hierarchy settings):
585 hierarchical_memory_limit # of bytes of memory limit with regard to
587 under which the memory cgroup is
588 hierarchical_memsw_limit # of bytes of memory+swap limit with regard to
589 hierarchy under which memory cgroup is.
612 Only anonymous and swap cache memory is listed as part of 'rss' stat.
614 amount of physical memory used by the cgroup.
619 mapped_file is accounted only when the memory cgroup is owner of page
636 A memory cgroup provides memory.failcnt and memory.memsw.failcnt files.
638 hit its limit. When a memory cgroup hits a limit, failcnt increases and
639 memory under it will be reclaimed.
643 # echo 0 > .../memory.failcnt
648 For efficiency, as other kernel components, memory cgroup uses some optimization
650 method and doesn't show 'exact' value of memory (and swap) usage, it's a fuzz
652 If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP)
653 value in memory.stat(see 5.2).
668 The output format of memory.numa_stat is::
681 The memory controller supports a deep hierarchy and hierarchical accounting.
694 In the diagram above, with hierarchical accounting enabled, all memory
706 For compatibility reasons writing 1 to memory.use_hierarchy will always pass::
708 # echo 1 > memory.use_hierarchy
715 Soft limits allow for greater sharing of memory. The idea behind soft limits
716 is to allow control groups to use as much of the memory as needed, provided
718 a. There is no memory contention
721 When the system detects memory contention or low memory, control groups
724 sure that one control group does not starve the others of memory.
727 no guarantees, but it does its best to make sure that when memory is
728 heavily contended for, memory is allocated based on the soft limit
738 # echo 256M > memory.soft_limit_in_bytes
742 # echo 1G > memory.soft_limit_in_bytes
746 reclaiming memory for balancing between memory cgroups
752 .. _cgroup-v1-memory-move-charges:
773 writing to memory.move_charge_at_immigrate of the destination cgroup.
777 # echo (some positive value) > memory.move_charge_at_immigrate
782 <cgroup-v1-memory-movable-charges>` for details.
790 try to make space by reclaiming memory. Task migration may fail if we
798 # echo 0 > memory.move_charge_at_immigrate
800 .. _cgroup-v1-memory-movable-charges:
808 (old) memory cgroup.
816 | 1 | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory) |
832 9. Memory thresholds
835 Memory cgroup implements memory thresholds using the cgroups notification
836 API (see cgroups.txt). It allows to register multiple memory and memsw
842 - open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
843 - write string like "<event_fd> <fd of memory.usage_in_bytes> <threshold>" to
846 Application will be notified through eventfd when memory usage crosses
851 .. _cgroup-v1-memory-oom-control:
858 memory.oom_control file is for OOM notification and other controls.
860 Memory cgroup implements OOM notifier using the cgroup notification
867 - open memory.oom_control file
868 - write string like "<event_fd> <fd of memory.oom_control>" to
874 You can disable the OOM-killer by writing "1" to memory.oom_control file, as:
876 #echo 1 > memory.oom_control
879 in memory cgroup's OOM-waitqueue when they request accountable memory.
881 For running them, you have to relax the memory cgroup's OOM status by
898 (if 1, the memory cgroup is under OOM, tasks may be stopped.)
903 11. Memory Pressure (DEPRECATED)
908 The pressure level notifications can be used to monitor the memory
910 different strategies of managing their memory resources. The pressure
913 The "low" level means that the system is reclaiming memory for new
919 The "medium" level means that the system is experiencing medium memory
922 vmstat/zoneinfo/memcg or internal memory usage statistics and free any
926 about to out of memory (OOM) or even the in-kernel OOM killer is on its
937 especially bad if we are low on memory or thrashing. Group B, will receive
949 example, groups A, B, and C will receive notification of memory pressure.
952 memory pressure is experienced in the memcg for which the notification is
954 registered for "local" notification and the group experiences memory
965 The file memory.pressure_level is only used to setup an eventfd. To
969 - open memory.pressure_level;
970 - write string as "<event_fd> <fd of memory.pressure_level> <level[,mode]>"
973 Application will be notified through eventfd when memory pressure is at
975 memory.pressure_level are no implemented.
980 memory limit, sets up a notification in the cgroup and then makes child
983 # cd /sys/fs/cgroup/memory/
986 # cgroup_event_listener memory.pressure_level low,hierarchy &
987 # echo 8000000 > memory.limit_in_bytes
988 # echo 8000000 > memory.memsw.limit_in_bytes
1006 Overall, the memory controller has been a stable controller and has been
1012 .. [1] Singh, Balbir. RFC: Memory Controller, http://lwn.net/Articles/206697/
1013 .. [2] Singh, Balbir. Memory Controller (RSS Control),
1029 10. Singh, Balbir. Memory controller v6 test results,
1032 .. [11] Singh, Balbir. Memory controller introduction (v6),
1034 .. [12] Corbet, Jonathan, Controlling memory use in cgroups,