tunnels: fix netns vs proto registration ordering

[safe/jmp/linux-2.6] / Documentation / cgroups / memory.txt

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 1a60887..b871f25 100644 (file)
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -152,14 +152,19 @@ When swap is accounted, following files are added.
 
 usage of mem+swap is limited by memsw.limit_in_bytes.
 
 
 usage of mem+swap is limited by memsw.limit_in_bytes.
 

-Note: why 'mem+swap' rather than swap.
+* 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
 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.
+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.

 
 

-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.
+* What happens when a cgroup hits memory.memsw.limit_in_bytes
+When a cgroup his memory.memsw.limit_in_bytes, it's useless to do swap-out
+in this cgroup. Then, swap-out will not be done by cgroup routine and file
+caches are dropped. But as mentioned above, global LRU can do swapout memory
+from it for sanity of the system's memory management state. You can't forbid
+it by cgroup.

 
 2.5 Reclaim
 
 
 2.5 Reclaim
 


@@ -174,6 +179,9 @@ The reclaim algorithm has not been modified for cgroups, except that
 pages that are selected for reclaiming come from the per cgroup LRU
 list.
 
 pages that are selected for reclaiming come from the per cgroup LRU
 list.
 

+NOTE: Reclaim does not work for the root cgroup, since we cannot set any
+limits on the root cgroup.
+

 2. Locking
 
 The memory controller uses the following hierarchy
 2. Locking
 
 The memory controller uses the following hierarchy


@@ -204,6 +212,8 @@ We can alter the memory limit:
 
 NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
 mega or gigabytes.
 
 NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
 mega or gigabytes.

+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
 
 # cat /cgroups/0/memory.limit_in_bytes
 4194304


@@ -369,7 +379,42 @@ cgroups created below it.
 
 NOTE2: This feature can be enabled/disabled per subtree.
 
 
 NOTE2: This feature can be enabled/disabled per subtree.
 

-7. TODO
+7. Soft limits
+
+Soft limits allow for greater sharing of memory. The idea behind soft limits
+is to allow control groups to use as much of the memory as needed, provided
+
+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
+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.
+
+Please note that soft limits is a best effort feature, it comes with
+no guarantees, but it does its best to make sure that when memory is
+heavily contended for, memory is allocated based on the soft limit
+hints/setup. Currently soft limit based reclaim is setup such that
+it gets invoked from balance_pgdat (kswapd).
+
+7.1 Interface
+
+Soft limits can be setup by using the following commands (in this example we
+assume a soft limit of 256 megabytes)
+
+# echo 256M > memory.soft_limit_in_bytes
+
+If we want to change this to 1G, we can at any time use
+
+# 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
+NOTE2: It is recommended to set the soft limit always below the hard limit,
+       otherwise the hard limit will take precedence.
+
+8. TODO

 
 1. Add support for accounting huge pages (as a separate controller)
 2. Make per-cgroup scanner reclaim not-shared pages first
 
 1. Add support for accounting huge pages (as a separate controller)
 2. Make per-cgroup scanner reclaim not-shared pages first