Lines Matching refs:memory
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
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
81 memory.stat show various statistics
82 memory.use_hierarchy set/show hierarchical account enabled
85 memory.force_empty trigger forced page reclaim
86 memory.pressure_level set memory pressure notifications
87 memory.swappiness set/show swappiness parameter of vmscan
89 memory.move_charge_at_immigrate set/show controls of moving charges
92 memory.oom_control set/show oom controls.
93 memory.numa_stat show the number of memory usage per numa
95 memory.kmem.limit_in_bytes Deprecated knob to set and read the kernel
96 memory hard limit. Kernel hard limit is not
100 Kernel memory is still charged and reported
101 by memory.kmem.usage_in_bytes.
102 memory.kmem.usage_in_bytes show current kernel memory allocation
103 memory.kmem.failcnt show the number of kernel memory usage
105 memory.kmem.max_usage_in_bytes show max kernel memory usage recorded
107 memory.kmem.tcp.limit_in_bytes set/show hard limit for tcp buf memory
108 memory.kmem.tcp.usage_in_bytes show current tcp buf memory allocation
109 memory.kmem.tcp.failcnt show the number of tcp buf memory usage
111 memory.kmem.tcp.max_usage_in_bytes show max tcp buf memory usage recorded
117 The memory controller has a long history. A request for comments for the memory
119 there were several implementations for memory control. The goal of the
121 for memory control. The first RSS controller was posted by Balbir Singh [2]_
125 raised to allow user space handling of OOM. The current memory controller is
135 memory, the same physical memory needs to be reused to accomplish the task.
137 The memory controller implementation has been divided into phases. These
142 3. Kernel user memory accounting and slab control
145 The memory controller is the first controller developed.
151 page_counter tracks the current memory usage and limit of the group of
152 processes associated with the controller. Each cgroup has a memory controller
194 (*) page_cgroup structure is allocated at boot/memory-hotplug time.
230 the cgroup that brought it in -- this will happen on memory pressure).
232 But see :ref:`section 8.2 <cgroup-v1-memory-movable-charges>` when moving a
244 - memory.memsw.usage_in_bytes.
245 - memory.memsw.limit_in_bytes.
247 memsw means memory+swap. Usage of memory+swap is limited by
250 Example: Assume a system with 4G of swap. A task which allocates 6G of memory
251 (by mistake) under 2G memory limitation will use all swap.
256 2.4.1 why 'memory+swap' rather than swap
260 to move account from memory to swap...there is no change in usage of
261 memory+swap. In other words, when we want to limit the usage of swap without
262 affecting global LRU, memory+swap limit is better than just limiting swap from
265 2.4.2. What happens when a cgroup hits memory.memsw.limit_in_bytes
268 When a cgroup hits memory.memsw.limit_in_bytes, it's useless to do swap-out
270 caches are dropped. But as mentioned above, global LRU can do swapout memory
271 from it for sanity of the system's memory management state. You can't forbid
279 to reclaim memory from the cgroup so as to make space for the new
282 cgroup. (See :ref:`10. OOM Control <cgroup-v1-memory-oom-control>` below.)
296 (See :ref:`oom_control <cgroup-v1-memory-oom-control>` section)
313 .. _cgroup-v1-memory-kernel-extension:
318 With the Kernel memory extension, the Memory Controller is able to limit
319 the amount of kernel memory used by the system. Kernel memory is fundamentally
320 different than user memory, since it can't be swapped out, which makes it
323 Kernel memory accounting is enabled for all memory cgroups by default. But
324 it can be disabled system-wide by passing cgroup.memory=nokmem to the kernel
325 at boot time. In this case, kernel memory will not be accounted at all.
327 Kernel memory limits are not imposed for the root cgroup. Usage for the root
328 cgroup may or may not be accounted. The memory used is accumulated into
329 memory.kmem.usage_in_bytes, or in a separate counter when it makes sense.
335 Currently no soft limit is implemented for kernel memory. It is future work
343 kernel memory, we prevent new processes from being created when the kernel
344 memory usage is too high.
354 sockets memory pressure:
355 some sockets protocols have memory pressure
359 tcp memory pressure:
360 sockets memory pressure for the tcp protocol.
365 Because the "kmem" counter is fed to the main user counter, kernel memory can
366 never be limited completely independently of user memory. Say "U" is the user
372 accounting. Kernel memory is completely ignored.
375 Kernel memory is a subset of the user memory. This setup is useful in
376 deployments where the total amount of memory per-cgroup is overcommitted.
377 Overcommitting kernel memory limits is definitely not recommended, since the
378 box can still run out of non-reclaimable memory.
380 never greater than the total memory, and freely set U at the cost of his
384 In the current implementation, memory reclaim will NOT be triggered for
390 triggered for the cgroup for both kinds of memory. This setup gives the
391 admin a unified view of memory, and it is also useful for people who just
392 want to track kernel memory usage.
404 # mkdir /sys/fs/cgroup/memory
405 # mount -t cgroup none /sys/fs/cgroup/memory -o memory
409 # mkdir /sys/fs/cgroup/memory/0
410 # echo $$ > /sys/fs/cgroup/memory/0/tasks
412 4. Since now we're in the 0 cgroup, we can alter the memory limit::
414 # echo 4M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes
418 # cat /sys/fs/cgroup/memory/0/memory.limit_in_bytes
435 # cat /sys/fs/cgroup/memory/0/memory.usage_in_bytes
441 availability of memory on the system. The user is required to re-read
444 # echo 1 > memory.limit_in_bytes
445 # cat memory.limit_in_bytes
448 The memory.failcnt field gives the number of times that the cgroup limit was
451 The memory.stat file gives accounting information. Now, the number of
459 Performance test is also important. To see pure memory controller's overhead,
468 Trying usual test under memory controller is always helpful.
470 .. _cgroup-v1-memory-test-troubleshoot:
479 2. The user is using anonymous memory and swap is turned off or too low
485 <cgroup-v1-memory-oom-control>` (below) and seeing what happens will be
488 .. _cgroup-v1-memory-test-task-migration:
499 See :ref:`8. "Move charges at task migration" <cgroup-v1-memory-move-charges>`
505 <cgroup-v1-memory-test-troubleshoot>` and :ref:`4.2
506 <cgroup-v1-memory-test-task-migration>`, a cgroup might have some charge
522 memory.force_empty interface is provided to make cgroup's memory usage empty.
525 # echo 0 > memory.force_empty
532 memory pressure happens. If you want to avoid that, force_empty will be useful.
537 memory.stat file includes following statistics:
539 * per-memory cgroup local status
542 cache # of bytes of page cache memory.
543 rss # of bytes of anonymous and swap cache memory (includes
547 pgpgin # of charging events to the memory cgroup. The charging
550 pgpgout # of uncharging events to the memory cgroup. The uncharging
557 inactive_anon # of bytes of anonymous and swap cache memory on inactive
559 active_anon # of bytes of anonymous and swap cache memory on active
561 inactive_file # of bytes of file-backed memory and MADV_FREE anonymous
562 memory (LazyFree pages) on inactive LRU list.
563 active_file # of bytes of file-backed memory on active LRU list.
564 unevictable # of bytes of memory that cannot be reclaimed (mlocked etc).
567 * status considering hierarchy (see memory.use_hierarchy settings):
570 hierarchical_memory_limit # of bytes of memory limit with regard to
572 under which the memory cgroup is
573 hierarchical_memsw_limit # of bytes of memory+swap limit with regard to
574 hierarchy under which memory cgroup is.
597 Only anonymous and swap cache memory is listed as part of 'rss' stat.
599 amount of physical memory used by the cgroup.
604 mapped_file is accounted only when the memory cgroup is owner of page
621 A memory cgroup provides memory.failcnt and memory.memsw.failcnt files.
623 hit its limit. When a memory cgroup hits a limit, failcnt increases and
624 memory under it will be reclaimed.
628 # echo 0 > .../memory.failcnt
633 For efficiency, as other kernel components, memory cgroup uses some optimization
635 method and doesn't show 'exact' value of memory (and swap) usage, it's a fuzz
637 If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP)
638 value in memory.stat(see 5.2).
653 The output format of memory.numa_stat is::
666 The memory controller supports a deep hierarchy and hierarchical accounting.
679 In the diagram above, with hierarchical accounting enabled, all memory
691 For compatibility reasons writing 1 to memory.use_hierarchy will always pass::
693 # echo 1 > memory.use_hierarchy
698 Soft limits allow for greater sharing of memory. The idea behind soft limits
699 is to allow control groups to use as much of the memory as needed, provided
701 a. There is no memory contention
704 When the system detects memory contention or low memory, control groups
707 sure that one control group does not starve the others of memory.
710 no guarantees, but it does its best to make sure that when memory is
711 heavily contended for, memory is allocated based on the soft limit
721 # echo 256M > memory.soft_limit_in_bytes
725 # echo 1G > memory.soft_limit_in_bytes
729 reclaiming memory for balancing between memory cgroups
735 .. _cgroup-v1-memory-move-charges:
756 writing to memory.move_charge_at_immigrate of the destination cgroup.
760 # echo (some positive value) > memory.move_charge_at_immigrate
765 <cgroup-v1-memory-movable-charges>` for details.
773 try to make space by reclaiming memory. Task migration may fail if we
781 # echo 0 > memory.move_charge_at_immigrate
783 .. _cgroup-v1-memory-movable-charges:
791 (old) memory cgroup.
799 | 1 | A charge of file pages (normal file, tmpfs file (e.g. ipc shared memory) |
818 Memory cgroup implements memory thresholds using the cgroups notification
819 API (see cgroups.txt). It allows to register multiple memory and memsw
825 - open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
826 - write string like "<event_fd> <fd of memory.usage_in_bytes> <threshold>" to
829 Application will be notified through eventfd when memory usage crosses
834 .. _cgroup-v1-memory-oom-control:
839 memory.oom_control file is for OOM notification and other controls.
848 - open memory.oom_control file
849 - write string like "<event_fd> <fd of memory.oom_control>" to
855 You can disable the OOM-killer by writing "1" to memory.oom_control file, as:
857 #echo 1 > memory.oom_control
860 in memory cgroup's OOM-waitqueue when they request accountable memory.
862 For running them, you have to relax the memory cgroup's OOM status by
879 (if 1, the memory cgroup is under OOM, tasks may be stopped.)
887 The pressure level notifications can be used to monitor the memory
889 different strategies of managing their memory resources. The pressure
892 The "low" level means that the system is reclaiming memory for new
898 The "medium" level means that the system is experiencing medium memory
901 vmstat/zoneinfo/memcg or internal memory usage statistics and free any
905 about to out of memory (OOM) or even the in-kernel OOM killer is on its
916 especially bad if we are low on memory or thrashing. Group B, will receive
928 example, groups A, B, and C will receive notification of memory pressure.
931 memory pressure is experienced in the memcg for which the notification is
933 registered for "local" notification and the group experiences memory
944 The file memory.pressure_level is only used to setup an eventfd. To
948 - open memory.pressure_level;
949 - write string as "<event_fd> <fd of memory.pressure_level> <level[,mode]>"
952 Application will be notified through eventfd when memory pressure is at
954 memory.pressure_level are no implemented.
959 memory limit, sets up a notification in the cgroup and then makes child
962 # cd /sys/fs/cgroup/memory/
965 # cgroup_event_listener memory.pressure_level low,hierarchy &
966 # echo 8000000 > memory.limit_in_bytes
967 # echo 8000000 > memory.memsw.limit_in_bytes
985 Overall, the memory controller has been a stable controller and has been
1013 .. [12] Corbet, Jonathan, Controlling memory use in cgroups,