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-rw-r--r--Documentation/controllers/memory.txt29
1 files changed, 27 insertions, 2 deletions
diff --git a/Documentation/controllers/memory.txt b/Documentation/controllers/memory.txt
index 9fe2d0e..05fe29a 100644
--- a/Documentation/controllers/memory.txt
+++ b/Documentation/controllers/memory.txt
@@ -137,12 +137,32 @@ 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).
-Exception: When you do swapoff and make swapped-out pages of shmem(tmpfs) to
+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 Reclaim
+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.
+
+When swap is accounted, following files are added.
+ - memory.memsw.usage_in_bytes.
+ - memory.memsw.limit_in_bytes.
+
+usage of mem+swap is limited by memsw.limit_in_bytes.
+
+Note: why 'mem+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 OS point
+of view.
+
+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
@@ -246,6 +266,11 @@ 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.
+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.
+
+
5. Misc. interfaces.
5.1 force_empty
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