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-rw-r--r--Documentation/cgroups/memory.txt37
1 files changed, 32 insertions, 5 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index cc0ebc5241b..4c95c0034a4 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -44,8 +44,8 @@ Features:
- oom-killer disable knob and oom-notifier
- Root cgroup has no limit controls.
- Kernel memory and Hugepages are not under control yet. We just manage
- pages on LRU. To add more controls, we have to take care of performance.
+ Kernel memory support is work in progress, and the current version provides
+ basically functionality. (See Section 2.7)
Brief summary of control files.
@@ -61,7 +61,7 @@ Brief summary of control files.
memory.failcnt # show the number of memory usage hits limits
memory.memsw.failcnt # show the number of memory+Swap hits limits
memory.max_usage_in_bytes # show max memory usage recorded
- memory.memsw.usage_in_bytes # show max memory+Swap usage recorded
+ memory.memsw.max_usage_in_bytes # show max memory+Swap usage recorded
memory.soft_limit_in_bytes # set/show soft limit of memory usage
memory.stat # show various statistics
memory.use_hierarchy # set/show hierarchical account enabled
@@ -72,6 +72,9 @@ Brief summary of control files.
memory.oom_control # set/show oom controls.
memory.numa_stat # show the number of memory usage per numa node
+ memory.kmem.tcp.limit_in_bytes # set/show hard limit for tcp buf memory
+ memory.kmem.tcp.usage_in_bytes # show current tcp buf memory allocation
+
1. History
The memory controller has a long history. A request for comments for the memory
@@ -255,6 +258,27 @@ When oom event notifier is registered, event will be delivered.
per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
zone->lru_lock, it has no lock of its own.
+2.7 Kernel Memory Extension (CONFIG_CGROUP_MEM_RES_CTLR_KMEM)
+
+With the Kernel memory extension, the Memory Controller is able to limit
+the amount of kernel memory used by the system. Kernel memory is fundamentally
+different than user memory, since it can't be swapped out, which makes it
+possible to DoS the system by consuming too much of this precious resource.
+
+Kernel memory limits are not imposed for the root cgroup. Usage for the root
+cgroup may or may not be accounted.
+
+Currently no soft limit is implemented for kernel memory. It is future work
+to trigger slab reclaim when those limits are reached.
+
+2.7.1 Current Kernel Memory resources accounted
+
+* sockets memory pressure: some sockets protocols have memory pressure
+thresholds. The Memory Controller allows them to be controlled individually
+per cgroup, instead of globally.
+
+* tcp memory pressure: sockets memory pressure for the tcp protocol.
+
3. User Interface
0. Configuration
@@ -386,8 +410,11 @@ memory.stat file includes following statistics
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).
+pgpgin - # of charging events to the memory cgroup. The charging
+ event happens each time a page is accounted as either mapped
+ anon page(RSS) or cache page(Page Cache) to the cgroup.
+pgpgout - # of uncharging events to the memory cgroup. The uncharging
+ event happens each time a page is unaccounted from the cgroup.
swap - # of bytes of swap usage
inactive_anon - # of bytes of anonymous memory and swap cache memory on
LRU list.