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The cmk configuration directory

CMK checkpoints state in a directory structure on disk. The checkpoint describes all configured "pools" and their options, the "CPU lists" for those pools, and the "tasks" currently assigned to each CPU list. The directory format is described below.

CMK filesystem configuration format

Example:

etc
└── cmk
    ├── lock
    └── pools
        ├── controlplane
        │   ├── 3,11
        │   │   └── tasks
        │   └── exclusive
        ├── dataplane
        │   ├── 4,12
        │   │   └── tasks
        │   ├── 5,13
        │   │   └── tasks
        │   ├── 6,14
        │   │   └── tasks
        │   ├── 7,15
        │   │   └── tasks
        │   └── exclusive
        └── infra
            ├── 0-2,8-10
            │   └── tasks
            └── exclusive

Where:

Path Meaning
/etc/cmk/lock A lock file to protect against conflicting concurrent modification.
/etc/cmk/pools/<pool> Directories, one per pool.
/etc/cmk/pools/<pool>/exclusive Determines whether each CPU list in the pool can be shared (value 0) or not (value 1). Shared CPU lists can accomodate multiple tasks simultaneously, while exclusive CPU lists may only be allocated to one task at a time.
/etc/cmk/pools/<pool>/<cpulist> Directories whose names conform to the Linux cpuset CPU list format.
/etc/cmk/pools/<pool>/<cpulist>/tasks A file containing a comma-separated list of the root Linux process IDs of containers to which the CPUset has been allocated.

Creating a new configuration

CMK can set up its own initial state. See cmk init doc for more information.

Configuration changes over time

cmk updates the configuration as follows:

  • The operator creates the initial configuration on each host, either manually or by using the cmk init helper program.
  • When tasks are launched via cmk isolate, an available CPU list for the requested pool is chosen. That CPU list's tasks file is updated to include the cmk isolate process ID.
  • After a task launched via cmk isolate dies, the associated CPU list's tasks file is updated to remove the cmk isolate process ID.
  • cmk reconcile asks the operating system about all process IDs in all pools. Process IDs that are no longer valid are removed from the tasks file. cmk reconcile should be configured to execute periodically on each host).