From: Balbir Singh The goal of this patch is to implement a virtual address space controller using cgroups. The documentation describes the controller, its goal and usage in further detail. This patch: Documentation patch - describes the goals and usage of the memrlimit controller. Signed-off-by: Balbir Singh Cc: Sudhir Kumar Cc: YAMAMOTO Takashi Cc: Paul Menage Cc: Li Zefan Cc: Pavel Emelianov Cc: Balbir Singh Cc: KAMEZAWA Hiroyuki Cc: David Rientjes Cc: Vivek Goyal Signed-off-by: Andrew Morton --- Documentation/controllers/memrlimit.txt | 29 ++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff -puN /dev/null Documentation/controllers/memrlimit.txt --- /dev/null +++ a/Documentation/controllers/memrlimit.txt @@ -0,0 +1,29 @@ +This controller is enabled by the CONFIG_CGROUP_MEMRLIMIT_CTLR option. Prior +to reading this documentation please read Documentation/cgroups.txt and +Documentation/controllers/memory.txt. Several of the principles of this +controller are similar to the memory resource controller. + +This controller framework is designed to be extensible to control any +memory resource limit with little effort. + +This new controller, controls the address space expansion of the tasks +belonging to a 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 +"rlimit.limit_in_bytes". The file is similar to "limit_in_bytes" w.r.t. the user +interface. Please see section 3 of the memory resource controller documentation +for more details on how to use the user interface to get and set values. + +The "memrlimit.usage_in_bytes" file provides information about the total address +space usage of the tasks in the cgroup, in bytes. + +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 its 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. _