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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/2] dm-ioband v0.0.3: The I/O bandwidth controller: Document
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? _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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