Here is the document of dm-ioband.
Based on 2.6.24
Signed-off-by: Ryo Tsuruta <ryov@xxxxxxxxxxxxx>
Signed-off-by: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
diff -uprN linux-2.6.24.orig/Documentation/device-mapper/ioband.txt
linux-2.6.24/Documentation/device-mapper/ioband.txt
--- linux-2.6.24.orig/Documentation/device-mapper/ioband.txt 1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.24/Documentation/device-mapper/ioband.txt 2008-02-05
19:09:41.000000000 +0900
@@ -0,0 +1,728 @@
+======================
+Document for dm-ioband
+======================
+
+Contents:
+ What's dm-ioband all about?
+ Differences from the CFQ I/O scheduler
+ How dm-ioband works
+ Setup and Installation
+ Getting started
+ Command Reference
+ Examples
+ TODO
+
+
+What's dm-ioband all about?
+===========================
+dm-ioband is an I/O bandwidth controller implemented as a device-mapper driver.
+Several jobs using the same physical device have to share the bandwidth of
+the device. dm-ioband gives bandwidth to each job according to its weight,
+which each job can set its own value to.
+
+At this time, a job is a group of processes with the same pid or pgrp or uid.
+There is also a plan to make it support cgroup. A job can also be a virtual
+machine such as KVM or Xen.
+
+ +------+ +------+ +------+ +------+ +------+ +------+
+ |cgroup| |cgroup| | the | | pid | | pid | | the | jobs
+ | A | | B | |others| | X | | Y | |others|
+ +--|---+ +--|---+ +--|---+ +--|---+ +--|---+ +--|---+
+ +--V----+---V---+----V---+ +--V----+---V---+----V---+
+ | group | group | default| | group | group | default| ioband groups
+ | | | group | | | | group |
+ +-------+-------+--------+ +-------+-------+--------+
+ | ioband1 | | ioband2 | ioband devices
+ +-----------|------------+ +-----------|------------+
+ +-----------V--------------+-------------V------------+
+ | | |
+ | sdb1 | sdb2 | physical devices
+ +--------------------------+--------------------------+
+
+
+Differences from the CFQ I/O scheduler
+======================================
+
+Dm-ioband is flexible to configure the bandwidth settings.
+
+Dm-ioband can work with any type of I/O scheduler such as the NOOP scheduler,
+which is often chosen for high-end storages, since it is implemented outside
+the I/O scheduling layer. It allows both of partition based bandwidth control
+and job --- a group of processes --- based control. In addition, it can
+set different configuration on each physical device to control its bandwidth.
+
+Meanwhile the current implementation of the CFQ scheduler has seven IO priority
+levels and all jobs whose processes have the same IO priority share the
+bandwidth assigned to this level between them. And IO priority is an attribute
+of a process so that it equally effects to all block devices.
+
+
+How dm-ioband works.
+====================
+Every ioband device has one ioband group, which by default is called the
+default group.
+
+Ioband devices can also have extra ioband groups in them. Each ioband group
+has a job to support and a weight. Proportional to the weight, dm-ioband gives
+tokens to the group.
+
+A group passes on I/O requests that its job issues to the underlying
+layer so long as it has tokens left, while requests are blocked
+if there aren't any tokens left in the group. One token is consumed each
+time the group passes on a request. dm-ioband will refill groups with tokens
+once all of groups that have requests on a given physical device use up their
+tokens.
+
+With this approach, a job running on an ioband group with large weight is
+guaranteed to be able to issue a large number of I/O requests.
+
+
+Setup and Installation
+======================
+
+Build a kernel with these options enabled:
+
+ CONFIG_MD
+ CONFIG_BLK_DEV_DM
+ CONFIG_DM_IOBAND
+
+If compiled as module, use modprobe to load dm-ioband.
+
+ # make modules
+ # make modules_install
+ # depmod -a
+ # modprobe dm-ioband
+
+"dmsetup targets" command shows all available device-mapper targets.
+"ioband" is displayed if dm-ioband has been loaded.
+
+ # dmsetup targets
+ ioband v0.0.3
+
+
+Getting started
+===============
+The following is a brief description how to control the I/O bandwidth of
+disks. In this description, we'll take one disk with two partitions as an
+example target.
+
+
+Create and map ioband devices
+-----------------------------
+Create two ioband devices "ioband1" and "ioband2" and map them to "/dev/sda1"
+and "/dev/sda2" respectively.
+
+ # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1" | \
+ dmsetup create ioband1
+ # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1" | \
+ dmsetup create ioband2
+
+If the commands are successful then the device files "/dev/mapper/ioband1"
+and "/dev/mapper/ioband2" will have been created.
+
+
+Bandwidth control
+-----------------
+In this example, weights of 40 and 10 will be assigned to "ioband1" and
+"ioband2" respectively. This is done using the following commands:
+
+ # dmsetup message ioband1 0 weight 40
+ # dmsetup message ioband2 0 weight 10
+
+After these commands, "ioband1" can use 80% --- 40/(40+10)*100 --- of the
+bandwidth of the physical disk "/dev/sda" while "ioband2" can use 20%.
+
+
+Additional bandwidth control
+----------------------------
+In this example two extra ioband groups are created on "ioband1".
+The first group consists of all the processes with user-id 1000 and the
+second group consists of all the processes with user-id 2000. Their
+weights are 30 and 20 respectively.
+
+ # dmsetup message ioband1 0 type user
+ # dmsetup message ioband1 0 attach 1000
+ # dmsetup message ioband1 0 attach 2000
+ # dmsetup message ioband1 0 weight 1000:30
+ # dmsetup message ioband1 0 weight 2000:20
+
+Now the processes in the user-id 1000 group can use 30% ---
+30/(30+20+40+10)*100 --- of the bandwidth of the physical disk.
+
+ ioband device ioband group weight
+ ioband1 user id 1000 30
+ ioband1 user id 2000 20
+ ioband1 default group(the other users) 40
+ ioband2 default group 10
+
+
+Remove the ioband devices
+-------------------------
+Remove the ioband devices when no longer used.
+
+ # dmsetup remove ioband1
+ # dmsetup remove ioband2
+
+
+Command Reference
+=================
+
+
+Create an ioband device
+-----------------------
+SYNOPSIS
+ dmsetup create IOBAND_DEVICE
+
+DESCRIPTION
+ Create an ioband device with the given name IOBAND_DEVICE. The following
+ arguments, which dmsetup command reads from standard input, are also
+ required.
+
+ Logical starting sector. This must be "0."
+ The number of sectors to use.
+ "ioband" as a target type.
+ The path name of the physical device.
+ Device group ID.
+ I/O throttling value (optional)
+ I/O limiting value (optional)
+
+ The same device group ID must be set among the ioband devices that share
+ the same bandwidth, which means they work on the same physical disk.
+ "The number of sectors to use" should be "the number of sectors the physical
+ device." I/O throttling value and I/O limiting value, which are described
+ later in this document, are optional.
+
+ If the command is successful, the device file
+ "/dev/device-mapper/IOBAND_DEVICE" will have been created.
+ An ioband group is also created and attached to IOBAND_DEVICE as the default
+ ioband group.
+
+EXAMPLE
+ Create an ioband device with the following parameters:
+ physical device = "/dev/sda1"
+ ioband device name = "ioband1"
+ device group ID = "1"
+ I/O throttling value = "10"
+ I/O limiting value = "200"
+
+ # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 10 200" | \
+ dmsetup create ioband1
+
+ Create two device groups (ID=1,2). The bandwidths of these device groups
+ will be individually controlled.
+
+ # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1" | \
+ dmsetup create ioband1
+ # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1" | \
+ dmsetup create ioband2
+ # echo "0 $(blockdev --getsize /dev/sdb3) ioband /dev/sdb3 2" | \
+ dmsetup create ioband3
+ # echo "0 $(blockdev --getsize /dev/sdb4) ioband /dev/sdb4 2" | \
+ dmsetup create ioband4
+
+
+Remove the ioband device
+------------------------
+SYNOPSIS
+ dmsetup remove IOBAND_DEVICE
+
+DESCRIPTION
+ Remove the specified ioband device IOBAND_DEVICE. All the band groups
+ attached to the ioband device are also removed automatically.
+
+EXAMPLE
+ Remove ioband device "ioband1."
+
+ # dmsetup remove ioband1
+
+
+Set an ioband group type
+--------------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 type TYPE
+
+DESCRIPTION
+ Set the ioband group type of the specified ioband device IOBAND_DEVICE. TYPE
+ must be one of "user", "gid", "pid" or "pgrp." Once the type is set, new
+ ioband groups can be created on IOBAND_DEVICE.
+
+EXAMPLE
+ Set the ioband group type of ioband device "ioband1" to "user."
+
+ # dmsetup message ioband1 0 type user
+
+
+Create an ioband group
+----------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 attach ID
+
+DESCRIPTION
+ Create an ioband group and attach it to IOBAND_DEVICE.
+ ID specifies user-id, group-id, process-id or process-group-id depending
+ the ioband group type of IOBAND_DEVICE.
+
+EXAMPLE
+ Create an ioband group which consists of all processes with user-id 1000 and
+ attach it to ioband device "ioband1."
+
+ # dmsetup message ioband1 0 type user
+ # dmsetup message ioband1 0 attach 1000
+
+
+Detach the ioband group
+-----------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 detach ID
+
+DESCRIPTION
+ Detach the ioband group specified by ID from ioband device IOBAND_DEVICE.
+
+EXAMPLE
+ Detach the ioband group with ID "2000" from ioband device "ioband2."
+
+ # dmsetup message ioband2 0 detach 1000
+
+
+Set the weight of an ioband group
+---------------------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 weight VAL
+ dmsetup message IOBAND_DEVICE 0 weight ID:VAL
+
+DESCRIPTION
+ Set the weight of the ioband group specified by ID. Set the weight of the
+ default ioband group of IOBAND_DEVICE if ID isn't specified.
+ The following example means that "ioband1" can use 80% --- 40/(40+10)*100
+ --- of the bandwidth of the physical disk while "ioband2" can use 20%.
+
+ # dmsetup message ioband1 0 weight 40
+ # dmsetup message ioband2 0 weight 10
+
+ The following lines have the same effect as the above:
+
+ # dmsetup message ioband1 0 weight 4
+ # dmsetup message ioband2 0 weight 1
+
+ VAL must be an integer larger than 0. The default value, which is assigned
+ to newly created ioband groups, is 100.
+
+EXAMPLE
+ Set the weight of the default ioband group of "ioband1" to 40.
+
+ # dmsetup message ioband1 0 weight 40
+
+ Set the weight of the ioband group of "ioband1" with ID "1000" to 10.
+
+ # dmsetup message ioband1 0 weight 1000:10
+
+
+Set the number of tokens
+------------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 token VAL
+
+DESCRIPTION
+ Set the number of tokens to VAL. According to their weight, this number of
+ tokens will be distributed to all the ioband groups on the physical device
+ to which ioband device IOBAND_DEVICE belongs when they use up their tokens.
+
+ VAL must be an integer greater than 0. The default is 2048.
+
+EXAMPLE
+ Set the number of tokens of the physical device to which "ioband1" belongs
+ to 256.
+
+ # dmsetup message ioband1 0 token 256
+
+
+Set I/O throttling
+------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 io_throttle VAL
+
+DESCRIPTION
+ Set the I/O throttling value of the physical disk to which ioband device
+ IOBAND_DEVICE belongs to VAL. Dm-ioband start to control the bandwidth
+ when the number of BIOs in progress on the physical disk exceeds this value.
+
+EXAMPLE
+ Set the I/O throttling value of "ioband1" to 16.
+
+ # dmsetup message ioband1 0 io_throttle 16
+
+
+Set I/O limiting
+----------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 io_limit VAL
+
+DESCRIPTION
+ Set the I/O limiting value of the physical disk to which ioband device
+ IOBAND_DEVICE belongs to VAL. Dm-ioband will block all I/O requests for
+ the physical device if the number of BIOs in progress on the physical disk
+ exceeds this value.
+
+EXAMPLE
+ Set the I/O limiting value of "ioband1" to 128.
+
+ # dmsetup message ioband1 0 io_limit 128
+
+
+Display settings
+----------------
+SYNOPSIS
+ dmsetup table --target ioband
+
+DESCRIPTION
+ Display the settings of all the ioband devices whose target type is "ioband."
+
+ The output format is as below:
+ ioband device name
+ starting sector of partition
+ partition size in sectors
+ target type
+ device number (major:minor)
+ device group ID
+ I/O throttle
+ I/O limit
+
+EXAMPLE
+ Display the setting of an ioband device configured such as:
+ device name = "ioband1"
+ starting sector of partition = "0"
+ partition size in sectors = "44371467"
+ target type = "ioband"
+ device number (major:minor) = "202:33"
+ device group ID = "128"
+ I/O throttle = "10"
+ I/O limit = "400"
+
+ # dmsetup table --target ioband
+ ioband1: 0 44371467 ioband 202:33 128 10 400
+
+Display Statistics
+------------------
+SYNOPSIS
+ dmsetup status --target ioband
+
+DESCRIPTION
+ Display the statistics of all the ioband devices whose target type is
+ "ioband."
+
+ The output format is as below. the first five columns shows:
+ ioband device name
+ logical start sector of the device (must be 0)
+ device size in sectors
+ target type (must be "ioband")
+ device group ID
+
+ The remaining columns show the statistics of each ioband group on the
+ band device. Each group uses seven columns for its statistics.
+ ioband group ID (-1 means default)
+ total read requests
+ delayed read requests
+ total read sectors
+ total write requests
+ delayed write requests
+ total write sectors
+
+EXAMPLE
+ The following output shows the statistics of two ioband devices. Ioband2 only
+ has the default ioband group and ioband1 has three (default, 1001, 1002)
+ ioband groups.
+
+ # dmsetup status
+ ioband2: 0 44371467 ioband 128 -1 143 90 424 122 78 352
+ ioband1: 0 44371467 ioband 128 -1 223 172 408 211 136 600 1001 166 107 \
+ 472 139 95 352 1002 211 146 520 210 147 504
+
+Reset status counter
+--------------------
+SYNOPSIS
+ dmsetup message IOBAND_DEVICE 0 reset
+
+DESCRIPTION
+ Reset the statistics of ioband device IOBAND_DEVICE.
+
+EXAMPLE
+ Reset the statistics of "ioband1."
+
+ # dmsetup message ioband1 0 reset
+
+
+Examples
+========
+
+
+Example #1: Bandwidth control on Partitions
+-------------------------------------------
+This example describes how to control the bandwidth with disk partitions.
+The following diagram illustrates the configuration of this example.
+You may want to run a database on /dev/mapper/ioband1 and web applications
+on /dev/mapper/ioband2.
+
+ /mnt1 /mnt2 mount points
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/mapper/ioband1 | | /dev/mapper/ioband2 | ioband devices
+ +--------------------------+ +--------------------------+
+ | default group | | default group | ioband groups
+ | (80) | | (40) | (weight)
+ +-------------|------------+ +-------------|------------+
+ | |
+ +-------------V--------------+---------------V------------+
+ | /dev/sda1 | /dev/sda2 | physical devices
+ +----------------------------+----------------------------+
+
+To setup the above configuration, follow these steps:
+
+ 1) Create ioband devices with the same device group ID.
+
+ # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1" | \
+ dmsetup create ioband1
+ # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1" | \
+ dmsetup create ioband2
+
+ 2) Assign weights of 80 and 40 to the default ioband groups respectively.
+
+ # dmsetup message ioband1 0 weight 80
+ # dmsetup message ioband2 0 weight 40
+
+ 3) Create filesystems on the ioband devices and mount them.
+
+ # mkfs.ext3 /dev/mapper/ioband1
+ # mount /dev/mapper/ioband1 /mnt1
+
+ # mkfs.ext3 /dev/mapper/ioband2
+ # mount /dev/mapper/ioband2 /mnt2
+
+
+
+Example #2: Bandwidth control on Logical Volumes
+------------------------------------------------
+This example is similar to the example #1 but it uses LVM logical volumes
+instead of disk partitions. This example shows how to configure ioband devices
+on two striped logical volumes.
+
+ /mnt1 /mnt2 mount points
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/mapper/ioband1 | | /dev/mapper/ioband2 | ioband devices
+ +--------------------------+ +--------------------------+
+ | default group | | default group | ioband groups
+ | (80) | | (40) | (weight)
+ +-------------|------------+ +-------------|------------+
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/mapper/lv0 | | /dev/mapper/lv1 | striped logical
+ | | | | volumes
+ +---------------------------------------------------------+
+ | vg0 | volume group
+ +-------------|------------------------------|------------+
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/sdb | | /dev/sdc | physical devices
+ +--------------------------+ +--------------------------+
+
+To setup the above configuration, follow these steps:
+
+ 1) Initialize the partitions for use by LVM.
+
+ # pvcreate /dev/sdb
+ # pvcreate /dev/sdc
+
+ 2) Create a new volume group named "vg0" with /dev/sdb and /dev/sdc.
+
+ # vgcreate vg0 /dev/sdb /dev/sdc
+
+ 3) Create two logical volumes in "vg0." The volumes have to be striped.
+
+ # lvcreate -n lv0 -i 2 -l 64 vg0 -L 1024M
+ # lvcreate -n lv1 -i 2 -l 64 vg0 -L 1024M
+
+The rest is the same as the example #1.
+
+ 4) Create ioband devices corresponding to each logical volume.
+
+ # echo "0 $(blockdev --getsize /dev/mapper/lv0) ioband /dev/mapper/lv0 1"\
+ | dmsetup create ioband1
+ # echo "0 $(blockdev --getsize /dev/mapper/lv1) ioband /dev/mapper/lv1 1"\
+ | dmsetup create ioband2
+
+ 5) Assign weights of 80 and 40 to the default ioband groups respectively.
+
+ # dmsetup message ioband1 0 weight 80
+ # dmsetup message ioband2 0 weight 40
+
+ 6) Create filesystems on the ioband devices and mount them.
+
+ # mkfs.ext3 /dev/mapper/ioband1
+ # mount /dev/mapper/ioband1 /mnt1
+
+ # mkfs.ext3 /dev/mapper/ioband2
+ # mount /dev/mapper/ioband2 /mnt2
+
+
+
+Example #3: Bandwidth control on processes
+------------------------------------------
+This example describes how to control the bandwidth with groups of processes.
+You may also want to run an additional application on the same machine
+described in the example #1. This example shows how to add a new ioband group
+for this application.
+
+
+ /mnt1 /mnt2 mount points
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/mapper/ioband1 | | /dev/mapper/ioband2 | ioband devices
+ +-------------+------------+ +-------------+------------+
+ | default | | user=1000 | default | ioband groups
+ | (80) | | (20) | (40) | (weight)
+ +-------------+------------+ +-------------+------------+
+ | |
+ +-------------V--------------+---------------V------------+
+ | /dev/sda1 | /dev/sda2 | physical device
+ +----------------------------+----------------------------+
+
+The following shows to set up a new ioband group on the machine that is already
+configured as the example #1. The application will have a weight of 20 and run
+with user-id 1000 on /dev/mapper/ioband2.
+
+
+ 1) Set the type of ioband2 to "user."
+ # dmsetup message ioband2 0 type user.
+
+ 2) Create a new ioband group on ioband2.
+ # dmsetup message ioband2 0 attach 1000
+
+ 3) Assign weight of 10 to this newly created ioband group.
+ # dmsetup message ioband2 0 weight 1000:20
+
+
+
+Example #4: Bandwidth control for Xen virtual block devices
+-----------------------------------------------------------
+
+This example describes how to control the bandwidth for Xen virtual
+block devices. The following diagram illustrates the configuration of
+this example.
+
+ Virtual Machine 1 Virtual Machine 2 virtual machines
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/xvda1 | | /dev/xvda1 | virtual block
+ +-------------|------------+ +-------------|------------+ devices
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/mapper/ioband1 | | /dev/mapper/ioband2 | ioband devices
+ +--------------------------+ +--------------------------+
+ | default group | | default group | ioband groups
+ | (80) | | (40) | (weight)
+ +-------------|------------+ +-------------|------------+
+ | |
+ +-------------V--------------+---------------V------------+
+ | /dev/sda1 | /dev/sda2 | physical device
+ +----------------------------+----------------------------+
+
+The followings shows how to map ioband device "ioband1" and "ioband2" to
+virtual block device "/dev/xvda1 on Virtual Machine 1" and "/dev/xvda1 on
+Virtual Machine 2" respectively on the machine configured as the example #1.
+Add the following lines to the configuration files that are referenced when
+creating "Virtual Machine 1" and "Virtual Machine 2."
+
+ For "Virtual Machine 1"
+ disk = [ 'phy:/dev/mapper/ioband1,xvda,w' ]
+
+ For "Virtual Machine 2"
+ disk = [ 'phy:/dev/mapper/ioband2,xvda,w' ]
+
+
+
+Example #5: Bandwidth control for Xen blktap devices
+----------------------------------------------------
+This example describes how to control the bandwidth for Xen virtual
+block devices when Xen blktap devices are used. The following diagram
+illustrates the configuration of this example.
+
+ Virtual Machine 1 Virtual Machine 2 virtual machines
+ | |
+ +-------------V------------+ +-------------V------------+
+ | /dev/xvda1 | | /dev/xvda1 | virtual block
+ +-------------|------------+ +-------------|------------+ devices
+ | |
+ +-------------V------------------------------V------------+
+ | /dev/mapper/ioband1 | ioband device
+ +----------------------------+----------------------------+
+ | default group | default group | ioband groups
+ | (80) | (40) | (weight)
+ +-------------|--------------+---------------|------------+
+ | |
+ +-------------|------------------------------|------------+
+ | +----------V----------+ +----------V---------+ |
+ | | vm1.img | | vm2.img | | disk image files
+ | +---------------------+ +--------------------+ |
+ | /vmdisk | mount point
+ +----------------------------|----------------------------+
+ |
+ +----------------------------V----------------------------+
+ | /dev/sda1 | physical device
+ +---------------------------------------------------------+
+
+To setup the above configuration, follow these steps:
+
+ 1) Create an ioband device.
+
+ # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1" | \
+ dmsetup create ioband1
+
+ 2) Add the following lines to the configuration files that are referenced
+ when creating "Virtual Machine 1" and "Virtual Machine 2."
+ Disk image files "/vmdisk/vm1.img" and "/vmdisk/vm2.img" will be used.
+
+ For "Virtual Machine 1"
+ disk = [ 'tap:aio:/vmdisk/vm1.img,xvda,w', ]
+
+ For "Virtual Machine 1"
+ disk = [ 'tap:aio:/vmdisk/vm2.img,xvda,w', ]
+
+ 3) Run the virtual machines.
+
+ # xm create vm1
+ # xm create vm2
+
+ 4) Find out the process IDs of the daemons which control the blktap devices.
+
+ # lsof /vmdisk/disk[12].img
+ COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
+ tapdisk 15011 root 11u REG 253,0 2147483648 48961 /vmdisk/vm1.img
+ tapdisk 15276 root 13u REG 253,0 2147483648 48962 /vmdisk/vm2.img
+
+ 5) Create new ioband groups of pid 15011 and pid 15276, which are process
+ IDs of the tapdisks, and assign weight of 80 and 40 to the groups
+ respectively.
+
+ # dmsetup message ioband1 0 type pid
+ # dmsetup message ioband1 0 attach 15011
+ # dmsetup message ioband1 0 weight 15011:80
+ # dmsetup message ioband1 0 attach 15276
+ # dmsetup message ioband1 0 weight 15276:40
+
+
+
+
+TODO
+====
+ - Cgroup support.
+ - Create a mechanism to track down which I/O is originally issued by which
+ process or cgroup.
+ - Control read and write requests separately.
+ - Support WRITE_BARRIER.
+ - Hierarchical ioband groups support.
+ - Optimization.
+ - More configuration tools. Or is the dmsetup command sufficient?
+ - Other policies to schedule BIOs. Or is the weight policy sufficient?
+ Is a new policy for LUNs, which may partially shared the bandwidth, needed?
+ - Other accounting policies to determine the bandwidths. Or is the number
+ of BIOs sufficient?
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