Messages in this thread Patch in this message | | | From | Balbir Singh <> | Date | Sun, 04 May 2008 03:08:25 +0530 | Subject | [-mm][PATCH 4/4] Add rlimit controller documentation |
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This is the documentation patch. It describes the rlimit controller and how to build and use it.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> ---
Documentation/controllers/rlimit.txt | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
diff -puN /dev/null Documentation/controllers/rlimit.txt --- /dev/null 2008-05-03 22:12:13.033285313 +0530 +++ linux-2.6.25-balbir/Documentation/controllers/rlimit.txt 2008-05-04 03:06:06.000000000 +0530 @@ -0,0 +1,29 @@ +This controller is enabled by the CONFIG_CGROUP_RLIMIT_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 +resource limit (memory related) 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 "rlimit.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. _ -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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