Re: [-mm][PATCH 1/4] Add memrlimit controller documentation (v4)

[Li Zefan <lizf@cn.fujitsu.com>]

Balbir Singh wrote:
> Documentation patch - describes the goals and usage of the memrlimit
> controller.
> 
> 
> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
> 
>  Documentation/controllers/memrlimit.txt |   29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff -puN /dev/null Documentation/controllers/memrlimit.txt
> --- /dev/null	2008-05-14 04:27:30.032276540 +0530
> +++ linux-2.6.26-rc2-balbir/Documentation/controllers/memrlimit.txt	2008-05-14 18:35:55.000000000 +0530
> @@ -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

    memrlimit.limit_in_bytes

> +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.
> _
> 

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