On Tue, 13 Apr 2010 11:34:06 +0530 Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-04-13 13:45:53]: > > > Thank you very much for your kindly helps!. > > -Kame > > = > > Documentation update. > > > > Some information are old, and I think current document doesn't work > > as "a guide for users". > > We need summary of all of our controls, at least. > > > > Changelog: 2010/04/12 > > * applied feedback > > > > Changelog: 2010/04/09 > > * replace 'lru' with 'LRU' and 'oom' with 'OOM' > > * fixed double-space breakage > > * applied all comments and fixed wrong parts pointed out. > > * fixed cgroup.procs > > > > Changelog: 2009/04/07 > > * fixed tons of typos. > > * replaced "memcg" with "memory cgroup" AMAP. > > * replaced "mem+swap" with "memory+swap" > > > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > --- > > Documentation/cgroups/memory.txt | 276 ++++++++++++++++++++++++++------------- > > 1 file changed, 188 insertions(+), 88 deletions(-) > > > > Index: mmotm-temp/Documentation/cgroups/memory.txt > > =================================================================== > > --- mmotm-temp.orig/Documentation/cgroups/memory.txt > > +++ mmotm-temp/Documentation/cgroups/memory.txt > > @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has > > to as the memory controller in this document. Do not confuse memory controller > > used here with the memory controller that is used in hardware. > > > > -Salient features > > - > > -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and > > - Swap Cache memory pages. > > -b. The infrastructure allows easy addition of other types of memory to control > > -c. Provides *zero overhead* for non memory controller users > > -d. Provides a double LRU: global memory pressure causes reclaim from the > > - global LRU; a cgroup on hitting a limit, reclaims from the per > > - cgroup LRU > > - > > Benefits and Purpose of the memory controller > > > > The memory controller isolates the memory behaviour of a group of tasks > > @@ -33,6 +23,45 @@ d. A CD/DVD burner could control the amo > > e. There are several other use cases, find one or use the controller just > > for fun (to learn and hack on the VM subsystem). > > > > +Current Status: linux-2.6.34-mmotm(development version of 2010/April) > > + > > +Features: > > + - accounting anonymous pages, file caches, swap caches usage and limit them. > > + - private LRU and reclaim routine. (system's global LRU and private LRU > > + work independently from each other) > > + - optionally, memory+swap usage can be accounted and limited. > > + - hierarchical accounting > > + - soft limit > > + - moving(recharging) account at moving a task is selectable. > > + - usage threshold notifier > > + - oom-killer disable knob and oom-notifier > > + - Root cgroup has no limit controls. > > + > > + Kernel memory and Hugepages are not under control yet. We just manage > > + pages on LRU. To add more controls, we have to take care of performance. > > + > > +Brief summary of control files. > > + > > + tasks # attach a task(thread) and show list of threads > > + cgroup.procs # show list of processes > > + cgroup.event_control # an interface for event_fd() > > + memory.usage_in_bytes # show current memory(RSS+Cache) usage. > > + memory.memsw.usage_in_bytes # show current memory+Swap usage > > + memory.limit_in_bytes # set/show limit of memory usage > > + memory.memsw.limit_in_bytes # set/show limit of memory+Swap usage > > + memory.failcnt # show the number of memory usage hits limits > > + memory.memsw.failcnt # show the number of memory+Swap hits limits > > + memory.max_usage_in_bytes # show max memory usage recorded > > + memory.memsw.usage_in_bytes # show max memory+Swap usage recorded > > + memory.soft_limit_in_bytes # set/show soft limit of memory usage > > + memory.stat # show various statistics > > + memory.use_hierarchy # set/show hierarchical account enabled > > + memory.force_empty # trigger forced move charge to parent > > + memory.swappiness # set/show swappiness parameter of vmscan > > + (See sysctl's vm.swappiness) > > + memory.move_charge_at_immigrate # set/show controls of moving charges > > + memory.oom_control # set/show oom controls. > > + > > Can we align the "#" comments, please! > It's aligned. > > 1. History > > > > The memory controller has a long history. A request for comments for the memory > > @@ -106,14 +135,14 @@ the necessary data structures and check > > is over its limit. If it is then reclaim is invoked on the cgroup. > > More details can be found in the reclaim section of this document. > > If everything goes well, a page meta-data-structure called page_cgroup is > > -allocated and associated with the page. This routine also adds the page to > > -the per cgroup LRU. > > +updated. page_cgroup has its own LRU on cgroup. > > +(*) page_cgroup structure is allocated at boot/memory-hotplug time. > > > > 2.2.1 Accounting details > > > > All mapped anon pages (RSS) and cache pages (Page Cache) are accounted. > > -(some pages which never be reclaimable and will not be on global LRU > > - are not accounted. we just accounts pages under usual vm management.) > > +Some pages which are never reclaimable and will not be on the global LRU > > +are not accounted. We just account pages under usual VM management. > > > > RSS pages are accounted at page_fault unless they've already been accounted > > for earlier. A file page will be accounted for as Page Cache when it's > > @@ -121,12 +150,19 @@ inserted into inode (radix-tree). While > > processes, duplicate accounting is carefully avoided. > > > > A RSS page is unaccounted when it's fully unmapped. A PageCache page is > > -unaccounted when it's removed from radix-tree. > > +unaccounted when it's removed from radix-tree. Even if RSS pages are fully > > +unmapped (by kswapd), they may exist as SwapCache in the system until they > > +are really freed. Such SwapCaches also also accounted. > > +A swapped-in page is not accounted until it's mapped. > > + > > +Note: The kernel does swapin-readahead and read multiple swaps at once. > > +This means swapped-in pages may contain pages for other tasks than a task > > +causing page fault. So, we avoid accounting at swap-in I/O. > > > > At page migration, accounting information is kept. > > > > -Note: we just account pages-on-lru because our purpose is to control amount > > -of used pages. not-on-lru pages are tend to be out-of-control from vm view. > > +Note: we just account pages-on-LRU because our purpose is to control amount > > +of used pages. not-on-LRU pages tend to be out-of-control from VM view. > > ^^ period might not be appropriate, if it is, n (not) should > be caps replaced with , > > > > 2.3 Shared Page Accounting > > > > @@ -143,6 +179,7 @@ caller of swapoff rather than the users > > > > > > 2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP) > > + > > Swap Extension allows you to record charge for swap. A swapped-in page is > > charged back to original page allocator if possible. > > > > @@ -150,13 +187,20 @@ When swap is accounted, following files > > - memory.memsw.usage_in_bytes. > > - memory.memsw.limit_in_bytes. > > > > -usage of mem+swap is limited by memsw.limit_in_bytes. > > +memsw means memory+swap. Usage of memory+swap is limited by > > +memsw.limit_in_bytes. > > > > -* why 'mem+swap' rather than swap. > > +Example: Assume a system with 4G of swap. A task which allocates 6G of memory > > +(by mistake) under 2G memory limitation will use all swap. > > +In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap. > > +By using memsw limit, you can avoid system OOM which can be caused by swap > > +shortage. > > + > > +* why 'memory+swap' rather than swap. > > The global LRU(kswapd) can swap out arbitrary pages. Swap-out means > > to move account from memory to swap...there is no change in usage of > > -mem+swap. In other words, when we want to limit the usage of swap without > > -affecting global LRU, mem+swap limit is better than just limiting swap from > > +memory+swap. In other words, when we want to limit the usage of swap without > > +affecting global LRU, memory+swap limit is better than just limiting swap from > > OS point of view. > > > > * What happens when a cgroup hits memory.memsw.limit_in_bytes > > @@ -168,12 +212,12 @@ it by cgroup. > > > > 2.5 Reclaim > > > > -Each cgroup maintains a per cgroup LRU that consists of an active > > -and inactive list. When a cgroup goes over its limit, we first try > > +Each cgroup maintains a per cgroup LRU which has the same structure as > > +global VM. When a cgroup goes over its limit, we first try > > to reclaim memory from the cgroup so as to make space for the new > > pages that the cgroup has touched. If the reclaim is unsuccessful, > > an OOM routine is invoked to select and kill the bulkiest task in the > > -cgroup. > > +cgroup. (See 10. OOM Control below.) > > > > The reclaim algorithm has not been modified for cgroups, except that > > pages that are selected for reclaiming come from the per cgroup LRU > > @@ -187,13 +231,19 @@ Note2: When panic_on_oom is set to "2", > > When oom event notifier is registered, event will be delivered. > > (See oom_control section) > > > > -2. Locking > > +2.6 Locking > > > > -The memory controller uses the following hierarchy > > + lock_page_cgroup()/unlock_page_cgroup() should not be called under > > + mapping->tree_lock. > > > > -1. zone->lru_lock is used for selecting pages to be isolated > > -2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone) > > -3. lock_page_cgroup() is used to protect page->page_cgroup > > + Other lock order is following: > > + PG_locked. > > + mm->page_table_lock > > + zone->lru_lock > > + lock_page_cgroup. > > + In many cases, just lock_page_cgroup() is called. > > + per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by > > + zone->lru_lock, it has no lock of its own. > > > > 3. User Interface > > > > @@ -202,6 +252,7 @@ The memory controller uses the following > > a. Enable CONFIG_CGROUPS > > b. Enable CONFIG_RESOURCE_COUNTERS > > c. Enable CONFIG_CGROUP_MEM_RES_CTLR > > +d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension) > > > > 1. Prepare the cgroups > > # mkdir -p /cgroups > > @@ -209,31 +260,29 @@ c. Enable CONFIG_CGROUP_MEM_RES_CTLR > > > > 2. Make the new group and move bash into it > > # mkdir /cgroups/0 > > -# echo $$ > /cgroups/0/tasks > > +# echo $$ > /cgroups/0/tasks > > > > Since now we're in the 0 cgroup, > > We can alter the memory limit: > > # echo 4M > /cgroups/0/memory.limit_in_bytes > > > > NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo, > > -mega or gigabytes. > > +mega or gigabytes. (Here, Kilo, Mega, Giga are Kibibytes, Mebibytes, Gibibytes.) > > + > > NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited). > > NOTE: We cannot set limits on the root cgroup any more. > > > > # cat /cgroups/0/memory.limit_in_bytes > > 4194304 > > > > -NOTE: The interface has now changed to display the usage in bytes > > -instead of pages > > - > > We can check the usage: > > # cat /cgroups/0/memory.usage_in_bytes > > 1216512 > > > > A successful write to this file does not guarantee a successful set of > > -this limit to the value written into the file. This can be due to a > > +this limit to the value written into the file. This can be due to a > > number of factors, such as rounding up to page boundaries or the total > > -availability of memory on the system. The user is required to re-read > > +availability of memory on the system. The user is required to re-read > > this file after a write to guarantee the value committed by the kernel. > > > > # echo 1 > memory.limit_in_bytes > > @@ -248,15 +297,25 @@ caches, RSS and Active pages/Inactive pa > > > > 4. Testing > > > > -Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11]. > > -Apart from that v6 has been tested with several applications and regular > > -daily use. The controller has also been tested on the PPC64, x86_64 and > > -UML platforms. > > +For testing features and implementation, see memcg_test.txt. > > + > > +Performance test is also important. To see pure memory cgroup's overhead, > > +testing on tmpfs will give you good numbers of small overheads. > > +Example: do kernel make on tmpfs. > > + > > +Page-fault scalability is also important. At measuring parallel > > +page fault test, multi-process test may be better than multi-thread > > +test because it has noise of shared objects/status. > > + > > +But the above two are testing extreme situations. > > +Trying usual test under memory cgroup is always helpful. > > + > > + > > Extra newline. > will remove > > > > 4.1 Troubleshooting > > > > Sometimes a user might find that the application under a cgroup is > > -terminated. There are several causes for this: > > +terminated by OOM killer. There are several causes for this: > > > > 1. The cgroup limit is too low (just too low to do anything useful) > > 2. The user is using anonymous memory and swap is turned off or too low > > @@ -264,6 +323,9 @@ terminated. There are several causes for > > A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of > > some of the pages cached in the cgroup (page cache pages). > > > > +To know what happens, disable OOM_Kill by 10. OOM Control(see below) and > > +seeing what happens will be helpful. > > + > > 4.2 Task migration > > > > When a task migrates from one cgroup to another, it's charge is not > > @@ -271,16 +333,19 @@ carried forward by default. The pages al > > remain charged to it, the charge is dropped when the page is freed or > > reclaimed. > > > > -Note: You can move charges of a task along with task migration. See 8. > > +You can move charges of a task along with task migration. > > +See 8. "Move charges at task migration" > > > > 4.3 Removing a cgroup > > > > A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a > > cgroup might have some charge associated with it, even though all > > -tasks have migrated away from it. > > -Such charges are freed(at default) or moved to its parent. When moved, > > -both of RSS and CACHES are moved to parent. > > -If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also. > > +tasks have migrated away from it. (because we charge against pages, not > > +against tasks.) > > + > > +Such charges are freed or moved to their parent. At moving, both of RSS > > +and CACHES are moved to parent. > > +rmdir() may return -EBUSY if freeing/moving fails. See 5.1 also. > > > > Charges recorded in swap information is not updated at removal of cgroup. > > Recorded information is discarded and a cgroup which uses swap (swapcache) > > @@ -296,10 +361,10 @@ will be charged as a new owner of it. > > > > # echo 0 > memory.force_empty > > > > - Almost all pages tracked by this memcg will be unmapped and freed. Some of > > - pages cannot be freed because it's locked or in-use. Such pages are moved > > - to parent and this cgroup will be empty. But this may return -EBUSY in > > - some too busy case. > > + Almost all pages tracked by this memory cgroup will be unmapped and freed. > > + Some pages cannot be freed because they are locked or in-use. Such pages are > > + moved to parent and this cgroup will be empty. This may return -EBUSY if > > + VM is too busy to free/move all pages immediately. > > > > Typical use case of this interface is that calling this before rmdir(). > > Because rmdir() moves all pages to parent, some out-of-use page caches can be > > @@ -309,19 +374,41 @@ will be charged as a new owner of it. > > > > memory.stat file includes following statistics > > > > +# per-memory cgroup local status > > cache - # of bytes of page cache memory. > > rss - # of bytes of anonymous and swap cache memory. > > +mapped_file - # of bytes of mapped file (includes tmpfs/shmem) > > pgpgin - # of pages paged in (equivalent to # of charging events). > > pgpgout - # of pages paged out (equivalent to # of uncharging events). > > -active_anon - # of bytes of anonymous and swap cache memory on active > > - lru list. > > +swap - # of bytes of swap usage > > inactive_anon - # of bytes of anonymous memory and swap cache memory on > > - inactive lru list. > > -active_file - # of bytes of file-backed memory on active lru list. > > -inactive_file - # of bytes of file-backed memory on inactive lru list. > > + LRU list. > > +active_anon - # of bytes of anonymous and swap cache memory on active > > + inactive LRU list. > > +inactive_file - # of bytes of file-backed memory on inactive LRU list. > > +active_file - # of bytes of file-backed memory on active LRU list. > > unevictable - # of bytes of memory that cannot be reclaimed (mlocked etc). > > > > -The following additional stats are dependent on CONFIG_DEBUG_VM. > > +# status considering hierarchy (see memory.use_hierarchy settings) > > + > > +hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy > > + under which the memory cgroup is > > +hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to > > + hierarchy under which memory cgroup is. > > + > > +total_cache - sum of all children's "cache" > > +total_rss - sum of all children's "rss" > > +total_mapped_file - sum of all children's "cache" > > +total_pgpgin - sum of all children's "pgpgin" > > +total_pgpgout - sum of all children's "pgpgout" > > +total_swap - sum of all children's "swap" > > +total_inactive_anon - sum of all children's "inactive_anon" > > +total_active_anon - sum of all children's "active_anon" > > +total_inactive_file - sum of all children's "inactive_file" > > +total_active_file - sum of all children's "active_file" > > +total_unevictable - sum of all children's "unevictable" > > + > > +# The following additional stats are dependent on CONFIG_DEBUG_VM. > > > > inactive_ratio - VM internal parameter. (see mm/page_alloc.c) > > recent_rotated_anon - VM internal parameter. (see mm/vmscan.c) > > @@ -330,24 +417,37 @@ recent_scanned_anon - VM internal parame > > recent_scanned_file - VM internal parameter. (see mm/vmscan.c) > > > > Can we align the data on the right, like for total_* data earlier. > It's aligned. > > Memo: > > - recent_rotated means recent frequency of lru rotation. > > - recent_scanned means recent # of scans to lru. > > + recent_rotated means recent frequency of LRU rotation. > > + recent_scanned means recent # of scans to LRU. > > showing for better debug please see the code for meanings. > > > > Note: > > Only anonymous and swap cache memory is listed as part of 'rss' stat. > > This should not be confused with the true 'resident set size' or the > > - amount of physical memory used by the cgroup. Per-cgroup rss > > - accounting is not done yet. > > + amount of physical memory used by the cgroup. > > + 'rss + file_mapped" will give you resident set size of cgroup. > > + (Note: file and shmem may be shared among other cgroups. In that case, > > + file_mapped is accounted only when the memory cgroup is owner of page > > + cache.) > > > > 5.3 swappiness > > - Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. > > > > - Following cgroups' swappiness can't be changed. > > - - root cgroup (uses /proc/sys/vm/swappiness). > > - - a cgroup which uses hierarchy and it has child cgroup. > > - - a cgroup which uses hierarchy and not the root of hierarchy. > > +Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. > > + > > +Following cgroups' swappiness can't be changed. > > +- root cgroup (uses /proc/sys/vm/swappiness). > > +- a cgroup which uses hierarchy and it has other cgroup(s) below it. > > +- a cgroup which uses hierarchy and not the root of hierarchy. > > + > > +5.4 failcnt > > + > > +A memory cgroup provides memory.failcnt and memory.memsw.failcnt files. > > +This failcnt(== failure count) shows the number of times that a usage counter > > +hit its limit. When a memory cgroup hits a limit, failcnt increases and > > +memory under it will be reclaimed. > > > > +You can reset failcnt by writing 0 to failcnt file. > > +# echo 0 > .../memory.failcnt > > > > 6. Hierarchy support > > > > @@ -366,13 +466,13 @@ hierarchy > > > > In the diagram above, with hierarchical accounting enabled, all memory > > usage of e, is accounted to its ancestors up until the root (i.e, c and root), > > -that has memory.use_hierarchy enabled. If one of the ancestors goes over its > > +that has memory.use_hierarchy enabled. If one of the ancestors goes over its > > limit, the reclaim algorithm reclaims from the tasks in the ancestor and the > > children of the ancestor. > > > > 6.1 Enabling hierarchical accounting and reclaim > > > > -The memory controller by default disables the hierarchy feature. Support > > +A memory cgroup by default disables the hierarchy feature. Support > > can be enabled by writing 1 to memory.use_hierarchy file of the root cgroup > > > > # echo 1 > memory.use_hierarchy > > @@ -382,10 +482,10 @@ The feature can be disabled by > > # echo 0 > memory.use_hierarchy > > > > NOTE1: Enabling/disabling will fail if the cgroup already has other > > -cgroups created below it. > > + cgroups created below it. > > > > NOTE2: When panic_on_oom is set to "2", the whole system will panic in > > -case of an oom event in any cgroup. > > + case of an OOM event in any cgroup. > > > > 7. Soft limits > > > > @@ -395,7 +495,7 @@ is to allow control groups to use as muc > > a. There is no memory contention > > b. They do not exceed their hard limit > > > > -When the system detects memory contention or low memory control groups > > +When the system detects memory contention or low memory, control groups > > are pushed back to their soft limits. If the soft limit of each control > > group is very high, they are pushed back as much as possible to make > > sure that one control group does not starve the others of memory. > > @@ -409,7 +509,7 @@ it gets invoked from balance_pgdat (kswa > > 7.1 Interface > > > > Soft limits can be setup by using the following commands (in this example we > > -assume a soft limit of 256 megabytes) > > +assume a soft limit of 256 MiB) > > > > # echo 256M > memory.soft_limit_in_bytes > > > > @@ -418,7 +518,7 @@ If we want to change this to 1G, we can > > # echo 1G > memory.soft_limit_in_bytes > > > > NOTE1: Soft limits take effect over a long period of time, since they involve > > - reclaiming memory for balancing between memory cgroups > > +reclaiming memory for balancing between memory cgroups > > NOTE2: It is recommended to set the soft limit always below the hard limit, > > otherwise the hard limit will take precedence. > > > > @@ -445,7 +545,7 @@ Note: Charges are moved only when you mo > > Note: If we cannot find enough space for the task in the destination cgroup, we > > try to make space by reclaiming memory. Task migration may fail if we > > cannot make enough space. > > -Note: It can take several seconds if you move charges in giga bytes order. > > +Note: It can take several seconds if you move charges much. > > > > And if you want disable it again: > > > > @@ -476,15 +576,15 @@ Note: More type of pages(e.g. file cache > > > > 9. Memory thresholds > > > > -Memory controler implements memory thresholds using cgroups notification > > +Memory cgroup implements memory thresholds using cgroups notification > > API (see cgroups.txt). It allows to register multiple memory and memsw > > thresholds and gets notifications when it crosses. > > > > To register a threshold application need: > > - - create an eventfd using eventfd(2); > > - - open memory.usage_in_bytes or memory.memsw.usage_in_bytes; > > - - write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to > > - cgroup.event_control. > > +- create an eventfd using eventfd(2); > > +- open memory.usage_in_bytes or memory.memsw.usage_in_bytes; > > +- write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to > > Do we need the <> around memory.usage_in_bytes > Hmm ? I'm not sure. Could you explain why you think removing <> is better ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>