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    Subject[PATCH 12/12] Documentation for Resource Groups
    12/12 - res_groups_docs

    Documentation describing important Resource Groups components such as
    resource group, shares, controllers, and the configfs based user interface.
    --

    Signed-Off-By: Chandra Seetharaman <sekharan@us.ibm.com>
    Signed-Off-By: Hubertus Franke <frankeh@us.ibm.com>
    Signed-Off-By: Shailabh Nagar <nagar@watson.ibm.com>
    Signed-Off-By: Gerrit Huizenga <gh@us.ibm.com>
    Signed-Off-By: Vivek Kashyap <kashyapv@us.ibm.com>
    Signed-Off-By: Matt Helsley <matthltc@us.ibm.com>

    res_groups_basics | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++
    res_groups_install | 29 +++++++++++++++++++++
    res_groups_usage | 53 +++++++++++++++++++++++++++++++++++++++
    3 files changed, 153 insertions(+)

    Index: linux-2617-rc3/Documentation/res_groups/res_groups_basics
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2617-rc3/Documentation/res_groups/res_groups_basics 2006-04-27 10:18:48.000000000 -0700
    @@ -0,0 +1,71 @@
    +Resource Groups Basics
    +-------------
    +A brief review of Resoruce Groups concepts and terminology will help make
    +installation and testing easier. For more details, please visit
    +http://ckrm.sf.net.
    +
    +Concept:
    +User defines a resource group, attaches some amount of resources to
    +the resource group, and associates tasks with that resource group. Tasks
    +belonging to that resource group will be bound by the amount of resource
    +that is assigned to that group.
    +
    +User interface for the Resource Groups is through configfs. Resource group
    +is depicted as as a directory. Hierarchy of resource groups can be
    +created in which children of a resource group share resources allotted to
    +the parent. Tasks can be attached to any resource group which is at any level.
    +There is no correlation between parent-child relationship of tasks and
    +the parent-child relationship of the resource groups they belong to.
    +
    +During fork(), resource group is inherited by a task. A privileged user can
    +reassign a task to any resource group.
    +
    +Characteristics of a resource group can be accessed/changed through the
    +following files under the directory representing the resource group:
    +
    +shares: allows changing shares of different resources managed by the
    + resource group
    +stats: shows statistics associated with each resources managed by the
    + resource group
    +members: allows assignment of tasks to a resource group and shows tasks
    + that are assigned to a resource group.
    +
    +Resource allocations of a resource group is resource group to the amount
    +of resources available to the resource group's parent.
    +Resource allocations for a resource group is controlled by the parameters:
    +
    +min_shares: Minimum amount shares that can be allocated by a resource group. A
    + special value of DONT_CARE(-3) means that there is no minimum
    + shares of a resource is specified. This resource group may not get
    + any resource if the system is running short on resources.
    +max_shares: Specifies the maximum amount of resource that is allowed to be
    + allocated by a resource group. A special value DONT_CARE(-3) mean
    + that there is no specific limit is specified, this resource group
    + can get all the resources available.
    +child_shares_divisor: total guarantee that is allowed among the children of
    + this resource group. In other words, the sum of "guarantee"s of all
    + children of this resource group cannot exit this number.
    +
    +Any of these parameter can have a special value, UNSUPPORTED(-2) meaning
    +that the specific controller does not support this parameter. User's
    +request to change the value will be ignored.
    +
    +None of this parameters neither absolute nor have any units associated with
    +them. These are just numbers that are used to calculate the absolute number
    +of resource available for a specific resource group.
    +
    +Absolute amount of minimum shares available for a resource group is
    +calculuated as:
    +
    + absolute minimum shares = (parent's absolute amount of resource) *
    + (resource group's min_shares / parent's child_shares_divisor)
    +
    +Maximum shares is also calculated in the same way.
    +
    +Root resource group is allocated all the resources available in the system.
    +In other words absolute amount of resource available for the root resource
    +group is same as that of what is available in the system.
    +
    +min_shares and max_shares are related to the parent, these values on
    +the root resource group have no effect. Similarly, child_shares_divisor
    +is related to children, and hence it has no effect on leaf resource groups.
    Index: linux-2617-rc3/Documentation/res_groups/res_groups_install
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2617-rc3/Documentation/res_groups/res_groups_install 2006-04-27 10:18:48.000000000 -0700
    @@ -0,0 +1,29 @@
    +1. Configure
    +
    +Select appropriate configuration options:
    +
    + Enable configfs filesystem:
    + File systems --->
    + Pseudo filesystems --->
    + <M> Userspace-driven configuration filesystem (EXPERIMENTAL)
    +
    + Enable Resource Group components:
    + General Setup --->
    + Resource Groups --->
    + [*] Resource Groups
    + <M> Resource Groups Configfs Subsystem (User API)
    + [*] Number of Tasks Resource Manager
    +
    +
    +2. Build, boot the kernel
    +
    +3. Enable rgcs
    +
    + # insmod <patchestree>/fs/configfs/configfs.ko # if compiled as module
    + # insmod <patchedtree>/kernel/res_config/rgcs.ko # if compiled in as module
    + # mount -t configfs none /config
    +
    + This will create the directory /config/res_groups which is the root of
    + classes.
    +
    +4. Work with class hierarchy as explained in the file res_groups_usage
    Index: linux-2617-rc3/Documentation/res_groups/res_groups_usage
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-2617-rc3/Documentation/res_groups/res_groups_usage 2006-04-27 10:18:48.000000000 -0700
    @@ -0,0 +1,53 @@
    +Usage of Resoruce Groups
    +------------------------
    +
    +1. Create a resource group
    +
    + # mkdir /config/res_groups/c1
    + creates a resource group named c1, while
    +
    +The newly created directory is automatically populated by magic files
    +shares, stats, members, and attrib.
    +
    +2. View default shares of a resource group
    +
    + # cat /config/res_groups/c1/shares
    + res=numtasks,min_shares=-3,max_shares=-3,child_total_divisor=100
    +
    + Above is the default value set for resources that have controllers
    + registered with Resource Groups framework.
    +
    +3. change shares of a specific resource in a resource group
    +
    + One or more of the following fields can/must be specified
    + res=<res_name> #mandatory
    + min_shares=<number>
    + max_shares=<number>
    + child_total_divisor=<number>
    + e.g.
    + # echo "res=numtasks,max_shares=20" > /config/res_groups/c1/shares
    +
    + If any of these parameters are not specified, the current value will be
    + retained.
    +
    +4. Move a task to a different resource group
    +
    + write the pid of the process to the destination resource group's members
    + file
    + # echo 1004 > /config/res_groups/c1/members
    +
    +5. Get a list of tasks assigned to a resource group
    +
    + # cat /config/res_groups/c1/members
    + lists pids of tasks belonging to c1
    +
    +6. Get statictics of different resources of a resource group
    +
    + # cat /config/res_groups/c1/stats
    + shows c1's statistics for each registered resource controller.
    +
    +7. Configuration settings for controllers
    + Configuration values for controller are available through module
    + parameter interfaces. Consult the controller specific documents for
    + details. For example, numtasks has it available through
    + /sys/module/numtasks/parameters.
    --

    ----------------------------------------------------------------------
    Chandra Seetharaman | Be careful what you choose....
    - sekharan@us.ibm.com | .......you may get it.
    ----------------------------------------------------------------------
    -
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