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