Diffstat (limited to 'Documentation/cgroups/memory.txt')
1 files changed, 16 insertions, 21 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 9b1067afb22..dd88540bb99 100644
@@ -184,12 +184,14 @@ behind this approach is that a cgroup that aggressively uses a shared
page will eventually get charged for it (once it is uncharged from
the cgroup that brought it in -- this will happen on memory pressure).
+But see section 8.2: when moving a task to another cgroup, its pages may
+be recharged to the new cgroup, if move_charge_at_immigrate has been chosen.
Exception: If CONFIG_CGROUP_CGROUP_MEM_RES_CTLR_SWAP is not used.
When you do swapoff and make swapped-out pages of shmem(tmpfs) to
be backed into memory in force, charges for pages are accounted against the
caller of swapoff rather than the users of shmem.
2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
Swap Extension allows you to record charge for swap. A swapped-in page is
@@ -374,14 +376,15 @@ cgroup might have some charge associated with it, even though all
tasks have migrated away from it. (because we charge against pages, not
-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.
+We move the stats to root (if use_hierarchy==0) or parent (if
+use_hierarchy==1), and no change on the charge except uncharging
+from the child.
Charges recorded in swap information is not updated at removal of cgroup.
Recorded information is discarded and a cgroup which uses swap (swapcache)
will be charged as a new owner of it.
+About use_hierarchy, see Section 6.
5. Misc. interfaces.
@@ -394,13 +397,15 @@ will be charged as a new owner of it.
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.
+ moved to parent(if use_hierarchy==1) or root (if use_hierarchy==0) and this
+ cgroup will be empty.
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
moved to the parent. If you want to avoid that, force_empty will be useful.
+ About use_hierarchy, see Section 6.
5.2 stat file
memory.stat file includes following statistics
@@ -430,17 +435,10 @@ hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
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"
+total_<counter> - # hierarchical version of <counter>, which in
+ addition to the cgroup's own value includes the
+ sum of all hierarchical children's values of
+ <counter>, i.e. total_cache
# The following additional stats are dependent on CONFIG_DEBUG_VM.
@@ -622,8 +620,7 @@ memory cgroup.
bit | what type of charges would be moved ?
0 | A charge of an anonymous page(or swap of it) used by the target task.
- | Those pages and swaps must be used only by the target task. You must
- | enable Swap Extension(see 2.4) to enable move of swap charges.
+ | You must enable Swap Extension(see 2.4) to enable move of swap charges.
1 | A charge of file pages(normal file, tmpfs file(e.g. ipc shared memory)
| and swaps of tmpfs file) mmapped by the target task. Unlike the case of
@@ -636,8 +633,6 @@ memory cgroup.
-- Implement madvise(2) to let users decide the vma to be moved or not to be
- All of moving charge operations are done under cgroup_mutex. It's not good
behavior to hold the mutex too long, so we may need some trick.