This patch is the documentation of dm-ioband, design overview, installation, command, reference and examples. Based on 2.6.27-rc5-mm1 Signed-off-by: Ryo Tsuruta <ryov@xxxxxxxxxxxxx> Signed-off-by: Hirokazu Takahashi <taka@xxxxxxxxxxxxx> diff -uprN linux-2.6.27-rc5-mm1.orig/Documentation/device-mapper/ioband.txt linux-2.6.27-rc5-mm1/Documentation/device-mapper/ioband.txt --- linux-2.6.27-rc5-mm1.orig/Documentation/device-mapper/ioband.txt 1970-01-01 09:00:00.000000000 +0900 +++ linux-2.6.27-rc5-mm1/Documentation/device-mapper/ioband.txt 2008-10-02 19:56:48.000000000 +0900 @@ -0,0 +1,938 @@ + Block I/O bandwidth control: dm-ioband + + ------------------------------------------------------- + + Table of Contents + + [1]What's dm-ioband all about? + + [2]Differences from the CFQ I/O scheduler + + [3]How dm-ioband works. + + [4]Setup and Installation + + [5]Getting started + + [6]Command Reference + + [7]Examples + +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. + + A job is a group of processes with the same pid or pgrp or uid or a + virtual machine such as KVM or Xen. A job can also be a cgroup by applying + the bio-cgroup patch, which can be found at + [8]http://people.valinux.co.jp/~ryov/bio-cgroup/. + + +------+ +------+ +------+ +------+ +------+ +------+ + |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 8 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. Tokens are refilled once all of + groups that have requests on a given physical device use up their tokens. + + There are two policies for token consumption. One is that a token is + consumed for each I/O request. The other is that a token is consumed for + each I/O sector, for example, one I/O request which consists of + 4Kbytes(512bytes * 8 sectors) read consumes 8 tokens. A user can choose + either policy. + + With this approach, a job running on an ioband group with large weight + is guaranteed a wide I/O bandwidth. + + -------------------------------------------------------------------------- + +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" and the version number are displayed when dm-ioband has been + loaded. + + # dmsetup targets | grep ioband + ioband v1.7.0 + + + -------------------------------------------------------------------------- + +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". "ioband1" is mapped + to "/dev/sda1" and has a weight of 40. "ioband2" is mapped to "/dev/sda2" + and has a weight of 10. "ioband1" can use 80% --- 40/(40+10)*100 --- of + the bandwidth of the physical disk "/dev/sda" while "ioband2" can use 20%. + + # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 0 0 none" \ + "weight 0 :40" | dmsetup create ioband1 + # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1 0 0 none" \ + "weight 0 :10" | dmsetup create ioband2 + + + If the commands are successful then the device files + "/dev/mapper/ioband1" and "/dev/mapper/ioband2" will have been created. + + -------------------------------------------------------------------------- + + 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. + + Table 1. Weight assignments + + +----------------------------------------------------------------+ + | ioband device | ioband group | ioband 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. + Generally, dmsetup reads a table from standard input. Each line of + the table specifies a single target and is of the form: + + start_sector num_sectors "ioband" device_file ioband_device_id \ + io_throttle io_limit ioband_group_type policy token_base \ + :weight [ioband_group_id:weight...] + + + start_sector, num_sectors + + The sector range of the underlying device where + dm-ioband maps. + + ioband + + Specify the string "ioband" as a target type. + + device_file + + Underlying device name. + + ioband_device_id + + The ID number for an ioband device. The same ID + must be set among the ioband devices that share the + same bandwidth, which means they work on the same + physical disk. + + io_throttle + + Dm-ioband starts to control the bandwidth when the + number of BIOs in progress exceeds this value. If 0 + is specified, dm-ioband uses the default value. + + io_limit + + Dm-ioband blocks all I/O requests for the + IOBAND_DEVICE when the number of BIOs in progress + exceeds this value. If 0 is specified, dm-ioband uses + the default value. + + ioband_group_type + + Specify how to evaluate the ioband group ID. The + type must be one of "none", "user", "gid", "pid" or + "pgrp." The type "cgroup" is enabled by applying the + bio-cgroup patch. Specify "none" if you don't need + any ioband groups other than the default ioband + group. + + policy + + Specify bandwidth control policy. A user can choose + either policy "weight" or "weight-iosize." + + weight + + This policy controls bandwidth + according to the proportional to the + weight of each ioband group based on the + number of I/O requests. + + weight-iosize + + This policy controls bandwidth + according to the proportional to the + weight of each ioband group based on the + number of I/O sectors. + + token_base + + The number of tokens which specified by token_base + will be distributed to all ioband groups according to + the proportional to the weight of each ioband group. + If 0 is specified, dm-ioband uses the default value. + + ioband_group_id:weight + + Set the weight of the ioband group specified by + ioband_group_id. If ioband_group_id is omitted, the + weight is assigned to the default ioband group. + + EXAMPLE + + Create an ioband device with the following parameters: + + * Starting sector = "0" + + * The number of sectors = "$(blockdev --getsize /dev/sda1)" + + * Target type = "ioband" + + * Underlying device name = "/dev/sda1" + + * Ioband device ID = "128" + + * I/O throttle = "10" + + * I/O limit = "400" + + * Ioband group type = "user" + + * Bandwidth control policy = "weight" + + * Token base = "2048" + + * Weight for the default ioband group = "100" + + * Weight for the ioband group 1000 = "80" + + * Weight for the ioband group 2000 = "20" + + * Ioband device name = "ioband1" + + # echo "0 $(blockdev --getsize /dev/sda1) ioband" \ + "/dev/sda1 128 10 400 user weight 2048 :100 1000:80 2000:20" \ + | 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" \ + "0 0 none weight 0 :80" | dmsetup create ioband1 + # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1" \ + "0 0 none weight 0 :20" | dmsetup create ioband2 + # echo "0 $(blockdev --getsize /dev/sdb3) ioband /dev/sdb3 2" \ + "0 0 none weight 0 :60" | dmsetup create ioband3 + # echo "0 $(blockdev --getsize /dev/sdb4) ioband /dev/sdb4 2" \ + "0 0 none weight 0 :40" | 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 "none", "user", "gid", "pid" or + "pgrp." The type "cgroup" is enabled by applying the bio-cgroup + patch. 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 bandwidth control policy + + SYNOPSIS + + dmsetup message IOBAND_DEVICE 0 policy policy + + DESCRIPTION + + Set bandwidth control policy. This command applies to all ioband + devices which have the same ioband device ID as IOBAND_DEVICE. A + user can choose either policy "weight" or "weight-iosize." + + weight + + This policy controls bandwidth according to the + proportional to the weight of each ioband group based + on the number of I/O requests. + + weight-iosize + + This policy controls bandwidth according to the + proportional to the weight of each ioband group based + on the number of I/O sectors. + + EXAMPLE + + Set bandwidth control policy of ioband devices which have the + same ioband device ID as "ioband1" to "weight-iosize." + + # dmsetup message ioband1 0 policy weight-iosize + + + -------------------------------------------------------------------------- + + 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 current table for the ioband device in a format. See + "dmsetup create" command for information on the table format. + + EXAMPLE + + The following output shows the current table of "ioband1." + + # dmsetup table --target ioband + ioband: 0 32129937 ioband1 8:29 128 10 400 user weight \ + 2048 :100 1000:80 2000:20 + + + -------------------------------------------------------------------------- + + 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 and assign + weights of 80 and 40 to the default ioband groups respectively. + + # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 0 0" \ + "none weight 0 :80" | dmsetup create ioband1 + # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1 0 0" \ + "none weight 0 :40" | dmsetup create ioband2 + + + 2. 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 -I 64 vg0 -L 1024M + # lvcreate -n lv1 -i 2 -I 64 vg0 -L 1024M + + + The rest is the same as the example #1. + + 4. Create ioband devices corresponding to each logical volume and + assign weights of 80 and 40 to the default ioband groups respectively. + + # echo "0 $(blockdev --getsize /dev/mapper/vg0-lv0)" \ + "ioband /dev/mapper/vg0-lv0 1 0 0 none weight 0 :80" | \ + dmsetup create ioband1 + # echo "0 $(blockdev --getsize /dev/mapper/vg0-lv1)" \ + "ioband /dev/mapper/vg0-lv1 1 0 0 none weight 0 :40" | \ + dmsetup create ioband2 + + + 5. 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 0 0 none weight 0 :100" | 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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
