cgroup: rename Documentation/cgroups/ to Documentation/cgroup-legacy/

In preparation for adding cgroup2 documentation, rename
Documentation/cgroups/ to Documentation/cgroup-legacy/.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 0 insertions, 280 deletions

diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt
deleted file mode 100644
index 8870b0212150..000000000000
--- a/Documentation/cgroups/memcg_test.txt
+++ /dev/null
@@ -1,280 +0,0 @@
-Memory Resource Controller(Memcg)  Implementation Memo.
-Last Updated: 2010/2
-Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34).
-
-Because VM is getting complex (one of reasons is memcg...), memcg's behavior
-is complex. This is a document for memcg's internal behavior.
-Please note that implementation details can be changed.
-
-(*) Topics on API should be in Documentation/cgroups/memory.txt)
-
-0. How to record usage ?
-   2 objects are used.
-
-   page_cgroup ....an object per page.
-	Allocated at boot or memory hotplug. Freed at memory hot removal.
-
-   swap_cgroup ... an entry per swp_entry.
-	Allocated at swapon(). Freed at swapoff().
-
-   The page_cgroup has USED bit and double count against a page_cgroup never
-   occurs. swap_cgroup is used only when a charged page is swapped-out.
-
-1. Charge
-
-   a page/swp_entry may be charged (usage += PAGE_SIZE) at
-
-	mem_cgroup_try_charge()
-
-2. Uncharge
-  a page/swp_entry may be uncharged (usage -= PAGE_SIZE) by
-
-	mem_cgroup_uncharge()
-	  Called when a page's refcount goes down to 0.
-
-	mem_cgroup_uncharge_swap()
-	  Called when swp_entry's refcnt goes down to 0. A charge against swap
-	  disappears.
-
-3. charge-commit-cancel
-	Memcg pages are charged in two steps:
-		mem_cgroup_try_charge()
-		mem_cgroup_commit_charge() or mem_cgroup_cancel_charge()
-
-	At try_charge(), there are no flags to say "this page is charged".
-	at this point, usage += PAGE_SIZE.
-
-	At commit(), the page is associated with the memcg.
-
-	At cancel(), simply usage -= PAGE_SIZE.
-
-Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
-
-4. Anonymous
-	Anonymous page is newly allocated at
-		  - page fault into MAP_ANONYMOUS mapping.
-		  - Copy-On-Write.
-
-	4.1 Swap-in.
-	At swap-in, the page is taken from swap-cache. There are 2 cases.
-
-	(a) If the SwapCache is newly allocated and read, it has no charges.
-	(b) If the SwapCache has been mapped by processes, it has been
-	    charged already.
-
-	4.2 Swap-out.
-	At swap-out, typical state transition is below.
-
-	(a) add to swap cache. (marked as SwapCache)
-	    swp_entry's refcnt += 1.
-	(b) fully unmapped.
-	    swp_entry's refcnt += # of ptes.
-	(c) write back to swap.
-	(d) delete from swap cache. (remove from SwapCache)
-	    swp_entry's refcnt -= 1.
-
-
-	Finally, at task exit,
-	(e) zap_pte() is called and swp_entry's refcnt -=1 -> 0.
-
-5. Page Cache
-   	Page Cache is charged at
-	- add_to_page_cache_locked().
-
-	The logic is very clear. (About migration, see below)
-	Note: __remove_from_page_cache() is called by remove_from_page_cache()
-	and __remove_mapping().
-
-6. Shmem(tmpfs) Page Cache
-	The best way to understand shmem's page state transition is to read
-	mm/shmem.c.
-	But brief explanation of the behavior of memcg around shmem will be
-	helpful to understand the logic.
-
-	Shmem's page (just leaf page, not direct/indirect block) can be on
-		- radix-tree of shmem's inode.
-		- SwapCache.
-		- Both on radix-tree and SwapCache. This happens at swap-in
-		  and swap-out,
-
-	It's charged when...
-	- A new page is added to shmem's radix-tree.
-	- A swp page is read. (move a charge from swap_cgroup to page_cgroup)
-
-7. Page Migration
-
-	mem_cgroup_migrate()
-
-8. LRU
-        Each memcg has its own private LRU. Now, its handling is under global
-	VM's control (means that it's handled under global zone->lru_lock).
-	Almost all routines around memcg's LRU is called by global LRU's
-	list management functions under zone->lru_lock().
-
-	A special function is mem_cgroup_isolate_pages(). This scans
-	memcg's private LRU and call __isolate_lru_page() to extract a page
-	from LRU.
-	(By __isolate_lru_page(), the page is removed from both of global and
-	 private LRU.)
-
-
-9. Typical Tests.
-
- Tests for racy cases.
-
- 9.1 Small limit to memcg.
-	When you do test to do racy case, it's good test to set memcg's limit
-	to be very small rather than GB. Many races found in the test under
-	xKB or xxMB limits.
-	(Memory behavior under GB and Memory behavior under MB shows very
-	 different situation.)
-
- 9.2 Shmem
-	Historically, memcg's shmem handling was poor and we saw some amount
-	of troubles here. This is because shmem is page-cache but can be
-	SwapCache. Test with shmem/tmpfs is always good test.
-
- 9.3 Migration
-	For NUMA, migration is an another special case. To do easy test, cpuset
-	is useful. Following is a sample script to do migration.
-
-	mount -t cgroup -o cpuset none /opt/cpuset
-
-	mkdir /opt/cpuset/01
-	echo 1 > /opt/cpuset/01/cpuset.cpus
-	echo 0 > /opt/cpuset/01/cpuset.mems
-	echo 1 > /opt/cpuset/01/cpuset.memory_migrate
-	mkdir /opt/cpuset/02
-	echo 1 > /opt/cpuset/02/cpuset.cpus
-	echo 1 > /opt/cpuset/02/cpuset.mems
-	echo 1 > /opt/cpuset/02/cpuset.memory_migrate
-
-	In above set, when you moves a task from 01 to 02, page migration to
-	node 0 to node 1 will occur. Following is a script to migrate all
-	under cpuset.
-	--
-	move_task()
-	{
-	for pid in $1
-        do
-                /bin/echo $pid >$2/tasks 2>/dev/null
-		echo -n $pid
-		echo -n " "
-        done
-	echo END
-	}
-
-	G1_TASK=`cat ${G1}/tasks`
-	G2_TASK=`cat ${G2}/tasks`
-	move_task "${G1_TASK}" ${G2} &
-	--
- 9.4 Memory hotplug.
-	memory hotplug test is one of good test.
-	to offline memory, do following.
-	# echo offline > /sys/devices/system/memory/memoryXXX/state
-	(XXX is the place of memory)
-	This is an easy way to test page migration, too.
-
- 9.5 mkdir/rmdir
-	When using hierarchy, mkdir/rmdir test should be done.
-	Use tests like the following.
-
-	echo 1 >/opt/cgroup/01/memory/use_hierarchy
-	mkdir /opt/cgroup/01/child_a
-	mkdir /opt/cgroup/01/child_b
-
-	set limit to 01.
-	add limit to 01/child_b
-	run jobs under child_a and child_b
-
-	create/delete following groups at random while jobs are running.
-	/opt/cgroup/01/child_a/child_aa
-	/opt/cgroup/01/child_b/child_bb
-	/opt/cgroup/01/child_c
-
-	running new jobs in new group is also good.
-
- 9.6 Mount with other subsystems.
-	Mounting with other subsystems is a good test because there is a
-	race and lock dependency with other cgroup subsystems.
-
-	example)
-	# mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices
-
-	and do task move, mkdir, rmdir etc...under this.
-
- 9.7 swapoff.
-	Besides management of swap is one of complicated parts of memcg,
-	call path of swap-in at swapoff is not same as usual swap-in path..
-	It's worth to be tested explicitly.
-
-	For example, test like following is good.
-	(Shell-A)
-	# mount -t cgroup none /cgroup -o memory
-	# mkdir /cgroup/test
-	# echo 40M > /cgroup/test/memory.limit_in_bytes
-	# echo 0 > /cgroup/test/tasks
-	Run malloc(100M) program under this. You'll see 60M of swaps.
-	(Shell-B)
-	# move all tasks in /cgroup/test to /cgroup
-	# /sbin/swapoff -a
-	# rmdir /cgroup/test
-	# kill malloc task.
-
-	Of course, tmpfs v.s. swapoff test should be tested, too.
-
- 9.8 OOM-Killer
-	Out-of-memory caused by memcg's limit will kill tasks under
-	the memcg. When hierarchy is used, a task under hierarchy
-	will be killed by the kernel.
-	In this case, panic_on_oom shouldn't be invoked and tasks
-	in other groups shouldn't be killed.
-
-	It's not difficult to cause OOM under memcg as following.
-	Case A) when you can swapoff
-	#swapoff -a
-	#echo 50M > /memory.limit_in_bytes
-	run 51M of malloc
-
-	Case B) when you use mem+swap limitation.
-	#echo 50M > memory.limit_in_bytes
-	#echo 50M > memory.memsw.limit_in_bytes
-	run 51M of malloc
-
- 9.9 Move charges at task migration
-	Charges associated with a task can be moved along with task migration.
-
-	(Shell-A)
-	#mkdir /cgroup/A
-	#echo $$ >/cgroup/A/tasks
-	run some programs which uses some amount of memory in /cgroup/A.
-
-	(Shell-B)
-	#mkdir /cgroup/B
-	#echo 1 >/cgroup/B/memory.move_charge_at_immigrate
-	#echo "pid of the program running in group A" >/cgroup/B/tasks
-
-	You can see charges have been moved by reading *.usage_in_bytes or
-	memory.stat of both A and B.
-	See 8.2 of Documentation/cgroups/memory.txt to see what value should be
-	written to move_charge_at_immigrate.
-
- 9.10 Memory thresholds
-	Memory controller implements memory thresholds using cgroups notification
-	API. You can use tools/cgroup/cgroup_event_listener.c to test it.
-
-	(Shell-A) Create cgroup and run event listener
-	# mkdir /cgroup/A
-	# ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M
-
-	(Shell-B) Add task to cgroup and try to allocate and free memory
-	# echo $$ >/cgroup/A/tasks
-	# a="$(dd if=/dev/zero bs=1M count=10)"
-	# a=
-
-	You will see message from cgroup_event_listener every time you cross
-	the thresholds.
-
-	Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds.
-
-	It's good idea to test root cgroup as well.