blockio

Overview ¶

Package blockio implements class-based cgroup blockio controller management for containers.

Input: configuration of classes with blockio controller parameters (weights, throttling) for sets of block devices.

Outputs: Option 1: Write blockio parameters of a class to a cgroup directory. Option 2: Return blockio parameters of a class in a OCI LinuxBlockIO

structure, that can be passed to OCI-compliant container
runtime.

Notes:

• Using Weight requires bfq or cfq I/O scheduler to be effective for the block devices where Weight is used.

Configuration example:

Classes:

  # Define a blockio class "LowPrioThrottled".
  # Containers in this class will be throttled and handled as
  # low priority in the I/O scheduler.

  LowPrioThrottled:

    # Weight without a Devices list specifies the default
    # I/O scheduler weight for all devices
    # that are not explicitly mentioned in following items.
    # This will be written to cgroups(.bfq).weight.
    # Weights range from 10 to 1000, the default is 100.

    - Weight: 80

    # Set all parameters for all /dev/sd* and /dev/vd* block
    # devices.

    - Devices:
        - /dev/sd[a-z]
        - /dev/vd[a-z]
      ThrottleReadBps: 50M   # max read bytes per second
      ThrottleWriteBps: 10M  # max write bytes per second
      ThrottleReadIOPS: 10k  # max read io operations per second
      ThrottleWriteIOPS: 5k  # max write io operations per second
      Weight: 50             # I/O scheduler (cfq/bfq) weight for
                             # these devices will be written to
                             # cgroups(.bfq).weight_device

    # Set parameters particularly for SSD devices.
    # This configuration overrides above configurations for those
    # /dev/sd* and /dev/vd* devices whose disk id contains "SSD".

    - Devices:
        - /dev/disk/by-id/*SSD*
      ThrottleReadBps: 100M
      ThrottleWriteBps: 40M
      # Not mentioning Throttle*IOPS means no I/O operations
      # throttling on matching devices.
      Weight: 50

  # Define a blockio class "HighPrioFullSpeed".
  # There is no throttling on these containers, and
  # they will be prioritized by the I/O scheduler.

  HighPrioFullSpeed:
    - Weight: 400

Usage example:

blockio.SetLogger(logrus.New())
if err := blockio.SetConfigFromFile("/etc/containers/blockio.yaml", false); err != nil {
    return err
}
// Output option 1: write directly to cgroup "/mytestgroup"
if err := blockio.SetCgroupClass("/mytestgroup", "LowPrioThrottled"); err != nil {
    return err
}
// Output option 2: OCI LinuxBlockIO of a blockio class
if lbio, err := blockio.OciLinuxBlockIO("LowPrioThrottled"); err != nil {
    return err
} else {
    fmt.Printf("OCI LinuxBlockIO for LowPrioThrottled:\n%+v\n", lbio)
}