-Memory Controller
+Memory Resource Controller
+
+NOTE: The Memory Resource Controller has been generically been referred
+to as the memory controller in this document. Do not confuse memory controller
+used here with the memory controller that is used in hardware.
Salient features
2.2.1 Accounting details
-All mapped pages (RSS) and unmapped user pages (Page Cache) are accounted.
-RSS pages are accounted at the time of page_add_*_rmap() unless they've already
-been accounted for earlier. A file page will be accounted for as Page Cache;
-it's mapped into the page tables of a process, duplicate accounting is carefully
-avoided. Page Cache pages are accounted at the time of add_to_page_cache().
-The corresponding routines that remove a page from the page tables or removes
-a page from Page Cache is used to decrement the accounting counters of the
-cgroup.
+All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
+(some pages which never be reclaimable and will not be on global LRU
+ are not accounted. we just accounts pages under usual vm management.)
+
+RSS pages are accounted at page_fault unless they've already been accounted
+for earlier. A file page will be accounted for as Page Cache when it's
+inserted into inode (radix-tree). While it's mapped into the page tables of
+processes, duplicate accounting is carefully avoided.
+
+A RSS page is unaccounted when it's fully unmapped. A PageCache page is
+unaccounted when it's removed from radix-tree.
+
+At page migration, accounting information is kept.
+
+Note: we just account pages-on-lru because our purpose is to control amount
+of used pages. not-on-lru pages are tend to be out-of-control from vm view.
2.3 Shared Page Accounting
a. Enable CONFIG_CGROUPS
b. Enable CONFIG_RESOURCE_COUNTERS
-c. Enable CONFIG_CGROUP_MEM_CONT
+c. Enable CONFIG_CGROUP_MEM_RES_CTLR
1. Prepare the cgroups
# mkdir -p /cgroups
Since now we're in the 0 cgroup,
We can alter the memory limit:
-# echo -n 4M > /cgroups/0/memory.limit_in_bytes
+# echo 4M > /cgroups/0/memory.limit_in_bytes
NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
mega or gigabytes.
# cat /cgroups/0/memory.limit_in_bytes
-4194304 Bytes
+4194304
NOTE: The interface has now changed to display the usage in bytes
instead of pages
We can check the usage:
# cat /cgroups/0/memory.usage_in_bytes
-1216512 Bytes
+1216512
A successful write to this file does not guarantee a successful set of
this limit to the value written into the file. This can be due to a
availability of memory on the system. The user is required to re-read
this file after a write to guarantee the value committed by the kernel.
-# echo -n 1 > memory.limit_in_bytes
+# echo 1 > memory.limit_in_bytes
# cat memory.limit_in_bytes
-4096 Bytes
+4096
The memory.failcnt field gives the number of times that the cgroup limit was
exceeded.
The memory.force_empty gives an interface to drop *all* charges by force.
-# echo -n 1 > memory.force_empty
+# echo 1 > memory.force_empty
will drop all charges in cgroup. Currently, this is maintained for test.
tasks have migrated away from it. Such charges are automatically dropped at
rmdir() if there are no tasks.
-4.4 Choosing what to account -- Page Cache (unmapped) vs RSS (mapped)?
-
-The type of memory accounted by the cgroup can be limited to just
-mapped pages by writing "1" to memory.control_type field
-
-echo -n 1 > memory.control_type
-
5. TODO
1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first
3. Teach controller to account for shared-pages
-4. Start reclamation when the limit is lowered
-5. Start reclamation in the background when the limit is
+4. Start reclamation in the background when the limit is
not yet hit but the usage is getting closer
Summary
3. Emelianov, Pavel. Resource controllers based on process cgroups
http://lkml.org/lkml/2007/3/6/198
4. Emelianov, Pavel. RSS controller based on process cgroups (v2)
- http://lkml.org/lkml/2007/4/9/74
+ http://lkml.org/lkml/2007/4/9/78
5. Emelianov, Pavel. RSS controller based on process cgroups (v3)
http://lkml.org/lkml/2007/5/30/244
6. Menage, Paul. Control Groups v10, http://lwn.net/Articles/236032/
7. Vaidyanathan, Srinivasan, Control Groups: Pagecache accounting and control
subsystem (v3), http://lwn.net/Articles/235534/
-8. Singh, Balbir. RSS controller V2 test results (lmbench),
+8. Singh, Balbir. RSS controller v2 test results (lmbench),
http://lkml.org/lkml/2007/5/17/232
-9. Singh, Balbir. RSS controller V2 AIM9 results
+9. Singh, Balbir. RSS controller v2 AIM9 results
http://lkml.org/lkml/2007/5/18/1
-10. Singh, Balbir. Memory controller v6 results,
+10. Singh, Balbir. Memory controller v6 test results,
http://lkml.org/lkml/2007/8/19/36
-11. Singh, Balbir. Memory controller v6, http://lkml.org/lkml/2007/8/17/69
+11. Singh, Balbir. Memory controller introduction (v6),
+ http://lkml.org/lkml/2007/8/17/69
12. Corbet, Jonathan, Controlling memory use in cgroups,
http://lwn.net/Articles/243795/
projects / linux-2.6-omap-h63xx.git / blobdiff