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Date: Fri, 9 Apr 2010 08:50:32 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Randy Dunlap <randy.dunlap@...cle.com> Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>, "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] memcg: update documentation v3 On Thu, 8 Apr 2010 10:32:09 -0700 Randy Dunlap <randy.dunlap@...cle.com> wrote: > On Thu, 8 Apr 2010 14:58:00 +0900 KAMEZAWA Hiroyuki wrote: > > > > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> > > Documentation update for memory cgroup > > > > Some informations 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. > > > > This patch updates information for current implementations and add a > > summary of interfaces. etc... > > I found some more... (below) > Thank you. > > > Changelog: > > - fixed tons of typos. > > - replaced "memcg" with "memory cgroup" AMAP. > > - replaced "mem+swap" with "memory+swap" > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> > > --- > > Documentation/cgroups/memory.txt | 210 ++++++++++++++++++++++++++++----------- > > 1 file changed, 152 insertions(+), 58 deletions(-) > > > > Index: mmotm-temp/Documentation/cgroups/memory.txt > > =================================================================== > > --- mmotm-temp.orig/Documentation/cgroups/memory.txt > > +++ mmotm-temp/Documentation/cgroups/memory.txt > > > @@ -121,12 +150,18 @@ 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. It's bacause we can't > > This is because > ok. > > +know a page will be finaly mapped at swapin-readahead happens. > > finally mapped until > > > + > > +A Cache pages is unaccounted when it's removed from inode (radix-tree). > > page > Ouch, again.. > > > > 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. > > +of used pages. not-on-lru pages are tend to be out-of-control from VM view. > > drop: are > Sure. > > > > 2.3 Shared Page Accounting > > > > > @@ -248,15 +296,24 @@ 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. > > Example: > ok. > > + > > +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 above 2 is testing extreme situation. Trying usual test under memory cgroup > > are testing extreme situations. > I always do this kind of mistake, Hm... > > +is always helpful. > > + > > > > 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 > > > @@ -296,10 +359,10 @@ 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 of pages cannot be freed because it's locked or in-use. Such pages are > > Some pages they are locked > Sure. > > + 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 +372,41 @@ 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 > > + lru list. > > +active_anon - # of bytes of anonymous and swap cache memory on active > > drop one space between: and swap > ok. > > inactive lru list. > > It would be better to use LRU throughout the file instead of using LRU in some > places and lru in others (except when referring to variable names, of course). > Ah, I'll use LRU. > > -active_file - # of bytes of file-backed memory on active 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) > > @@ -337,17 +422,26 @@ Memo: > > 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 amoung 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 it has other cgroup(s) below it. > > - a cgroup which uses hierarchy and not the root of hierarchy. > > > > +5.4 failcnt > > + > > +The memory controller 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 controller hit a limit, failcnt increases and > > hits > ok. > > +memory under it will be reclaimed. > > > > 6. Hierarchy support > > > > > @@ -513,9 +607,9 @@ As. > > > > This operation is only allowed to the top cgroup of subhierarchy. > > If oom-killer is disabled, tasks under cgroup will hang/sleep > > -in memcg's oom-waitq when they request accountable memory. > > +in memory cgroup's oom-waitq when they request accountable memory. > > > > -For running them, you have to relax the memcg's oom sitaution by > > +For running them, you have to relax the memory cgroup's oom sitaution by > > It would be better to use OOM instead of oom throughout the file... > yes, I'll rewrite. > > * enlarge limit or reduce usage. > > To reduce usage, > > * kill some tasks. > > @@ -526,7 +620,7 @@ Then, stopped tasks will work again. > > > > At reading, current status of OOM is shown. > > oom_kill_disable 0 or 1 (if 1, oom-killer is disabled) > > - under_oom 0 or 1 (if 1, the memcg is under OOM,tasks may > > + under_oom 0 or 1 (if 1, the memory cgroup is under OOM,tasks may > > space after: OOM, tasks may > Ragards. -Kame > > be stopped.) > > > > 11. TODO > > > > -- > > > --- > ~Randy > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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