This patch adds documentation for virtual address space control.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
Documentation/controllers/memory.txt | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff -puN Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation Documentation/controllers/memory.txt
--- linux-2.6.25-rc5/Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation 2008-03-16 22:57:44.000000000 +0530
+++ linux-2.6.25-rc5-balbir/Documentation/controllers/memory.txt 2008-03-16 22:57:44.000000000 +0530
@@ -237,7 +237,31 @@ cgroup might have some charge associated
tasks have migrated away from it. Such charges are automatically dropped at
rmdir() if there are no tasks.
-5. TODO
+5. Virtual address space accounting
+
+A new resource counter controls the address space expansion of the tasks in
+the cgroup. Address space control is provided along the same lines as
+RLIMIT_AS control, which is available via getrlimit(2)/setrlimit(2).
+The interface for controlling address space is provided through
+"as_limit_in_bytes". The file is similar to "limit_in_bytes" w.r.t the user
+interface. Please see section 3 for more details on how to use the user
+interface to get and set values.
+
+The "as_usage_in_bytes" file provides information about the total address
+space usage of the cgroup in bytes.
+
+5.1 Advantages of providing this feature
+
+1. Control over virtual address space allows for a cgroup to fail gracefully
+ i.e, via a malloc or mmap failure as compared to OOM kill when no
+ pages can be reclaimed
+2. It provides better control over how many pages can be swapped out when
+ the cgroup goes over it's limit. A badly setup cgroup can cause excessive
+ swapping. Providing control over the address space allocations ensures
+ that the system administrator has control over the total swapping that
+ can take place.
+
+6. TODO
1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first
_
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
--
