NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | REGIONS, AREAS, AND GROUPS | FILE MAPPING | REPORT FIELDS | EXAMPLES | AUTHORS | SEE ALSO | COLOPHON

DMSTATS(8)                  MAINTENANCE COMMANDS                  DMSTATS(8)

NAME         top

       dmstats — device-mapper statistics management

SYNOPSIS         top

       dmsetup stats command [OPTIONS]

       dmstats command device_name | --major major --minor minor | -u|--uuid
              uuid [-v|--verbose]
       dmstats clear device_name [--allprograms|--programid id]
              [--allregions|--regionid id]
       dmstats create device_name...|file_path...|--alldevices [--areas
              nr_areas|--areasize area_size] [--bounds histogram_boundaries]
              [--filemap] [--follow follow_mode] [--foreground]
              [--nomonitor] [--nogroup] [--precise] [--start start_sector
              --length length|--segments] [--userdata user_data]
              [--programid id]
       dmstats delete device_name|--alldevices [--allprograms|--programid
              id] [--allregions|--regionid id]
       dmstats group [device_name|--alldevices] [--alias name] [--regions
              regions]
       dmstats help [-c|-C|--columns]
       dmstats list [device_name] [--histogram] [--allprograms|--programid
              id] [--units units] [--area] [--region] [--group] [--nosuffix]
              [--notimesuffix] [-v|--verbose]
       dmstats print [device_name] [--clear] [--allprograms|--programid id]
              [--allregions|--regionid id]
       dmstats report [device_name] [--interval seconds] [--count count]
              [--units units] [--histogram] [--allprograms|--programid id]
              [--allregions|--regionid id] [--area] [--region] [--group]
              [-O|--sort sort_fields] [-S|--select selection] [--units
              units] [--nosuffix] [--notimesuffix]
       dmstats ungroup [device_name|--alldevices] [--groupid id]
       dmstats update_filemap file_path [--groupid id] [--follow
              follow_mode] [--foreground]

DESCRIPTION         top

       The dmstats program manages IO statistics regions for devices that
       use the device-mapper driver. Statistics regions may be created,
       deleted, listed and reported on using the tool.

       The first argument to dmstats is a command.

       The second argument is the device name, uuid or major and minor
       numbers.

       Further options permit the selection of regions, output format
       control, and reporting behaviour.

       When no device argument is given dmstats will by default operate on
       all device-mapper devices present. The create and delete commands
       require the use of --alldevices when used in this way.

OPTIONS         top

       --alias name
              Specify an alias name for a group.

       --alldevices
              If no device arguments are given allow operation on all
              devices when creating or deleting regions.

       --allprograms
              Include regions from all program IDs for list and report
              operations.

       --allregions
              Include all present regions for commands that normally accept
              a single region identifier.

       --area
              When peforming a list or report, include objects of type area
              in the results.

       --areas nr_areas
              Specify the number of statistics areas to create within a new
              region.

       --areasize area_size[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
              Specify the size of areas into which a new region should be
              divided. An optional suffix selects units of: (b)ytes,
              (s)ectors, (k)ilobytes, (m)egabytes, (g)igabytes, (t)erabytes,
              (p)etabytes, (e)xabytes.  Capitalise to use multiples of 1000
              (S.I.) instead of 1024.

       --clear
              When printing statistics counters, also atomically reset them
              to zero.

       --count count
              Specify the iteration count for repeating reports. If the
              count argument is zero reports will continue to repeat until
              interrupted.

       --group
              When peforming a list or report, include objects of type group
              in the results.

       --filemap
              Instead of creating regions on a device as specified by
              command line options, open the file found at each file_path
              argument, and create regions corresponding to the locations of
              the on-disk extents allocated to the file(s).

       --nomonitor
              Disable the dmfilemapd daemon when creating new file mapped
              groups. Normally the device-mapper filemap monitoring daemon,
              dmfilemapd, is started for each file mapped group to update
              the set of regions as the file changes on-disk: use of this
              option disables this behaviour.

              Regions in the group may still be updated with the
              update_filemap command, or by starting the daemon manually.

       --follow follow_mode
              Specify the dmfilemapd file following mode. The file map
              monitoring daemon can monitor files in two distinct ways: the
              mode affects the behaviour of the daemon when a file under
              monitoring is renamed or unlinked, and the conditions which
              cause the daemon to terminate.

              The follow_mode argument is either "inode", for follow-inode
              mode, or "path", for follow-path.

              If follow-inode mode is used, the daemon will hold the file
              open, and continue to update regions from the same file
              descriptor. This means that the mapping will follow rename,
              move (within the same file system), and unlink operations.
              This mode is useful if the file is expected to be moved,
              renamed, or unlinked while it is being monitored.

              In follow-inode mode, the daemon will exit once it detects
              that the file has been unlinked and it is the last holder of a
              reference to it.

              If follow-path is used, the daemon will re-open the provided
              path on each monitoring iteration. This means that the group
              will be updated to reflect a new file being moved to the same
              path as the original file. This mode is useful for files that
              are expected to be updated via unlink and rename.

              In follow-path mode, the daemon will exit if the file is
              removed and not replaced within a brief tolerance interval.

              In either mode, the daemon exits automatically if the
              monitored group is removed.

       --foreground
              Specify that the dmfilemapd daemon should run in the
              foreground.  The daemon will not fork into the background, and
              will replace the dmstats command that started it.

       --groupid id
              Specify the group to operate on.

       --bounds histogram_boundaries[ns|us|ms|s]
              Specify the boundaries of a latency histogram to be tracked
              for the region as a comma separated list of latency values.
              Latency values are given in nanoseconds. An optional unit
              suffix of ns, us, ms, or s may be given after each value to
              specify units of nanoseconds, microseconds, miliseconds or
              seconds respectively.

       --histogram
              When used with the report and list commands select default
              fields that emphasize latency histogram data.

       --interval seconds
              Specify the interval in seconds between successive iterations
              for repeating reports. If --interval is specified but --count
              is not, reports will continue to repeat until interrupted.

       --length length[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
              Specify the length of a new statistics region in sectors. An
              optional suffix selects units of: (b)ytes, (s)ectors,
              (k)ilobytes, (m)egabytes, (g)igabytes, (t)erabytes,
              (p)etabytes, (e)xabytes.  Capitalise to use multiples of 1000
              (S.I.) instead of 1024.

       -j|--major major
              Specify the major number.

       -m|--minor minor
              Specify the minor number.

       --nogroup
              When creating regions mapping the extents of a file in the
              file system, do not create a group or set an alias.

       --nosuffix
              Suppress the suffix on output sizes.  Use with --units (except
              h and H) if processing the output.

       --notimesuffix
              Suppress the suffix on output time values. Histogram boundary
              values will be reported in units of nanoseconds.

       -o|--options
              Specify which report fields to display.

       -O|--sort sort_fields
              Sort output according to the list of fields given. Precede any
              sort field with '-' for a reverse sort on that column.

       --precise
              Attempt to use nanosecond precision counters when creating new
              statistics regions.

       --programid id
              Specify a program ID string. When creating new statistics
              regions this string is stored with the region. Subsequent
              operations may supply a program ID in order to select only
              regions with a matching value. The default program ID for
              dmstats-managed regions is "dmstats".

       --region
              When peforming a list or report, include objects of type
              region in the results.

       --regionid id
              Specify the region to operate on.

       --regions region_list
              Specify a list of regions to group. The group list is a comma-
              separated list of region identifiers. Continuous sequences of
              identifiers may be expressed as a hyphen separated range, for
              example: '1-10'.

       --relative
              If displaying the histogram report show relative (percentage)
              values instead of absolute counts.

       -S|--select selection
              Display only rows that match selection criteria. All rows with
              the additional "selected" column (-o selected) showing 1 if
              the row matches the selection and 0 otherwise. The selection
              criteria are defined by specifying column names and their
              valid values while making use of supported comparison
              operators.

       --start start[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
              Specify the start offset of a new statistics region in
              sectors. An optional suffix selects units of: (b)ytes,
              (s)ectors, (k)ilobytes, (m)egabytes, (g)igabytes, (t)erabytes,
              (p)etabytes, (e)xabytes.  Capitalise to use multiples of 1000
              (S.I.) instead of 1024.

       --segments
              When used with create, create a new statistics region for each
              target contained in the given device(s). This causes a
              separate region to be allocated for each segment of the
              device.

              The newly created regions are automatically placed into a
              group unless the --nogroup option is given. When grouping is
              enabled a group alias may be specified using the --alias
              option.

       --units [units][h|H|b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E]
              Set the display units for report output.  All sizes are output
              in these units: (h)uman-readable, (b)ytes, (s)ectors,
              (k)ilobytes, (m)egabytes, (g)igabytes, (t)erabytes,
              (p)etabytes, (e)xabytes.  Capitalise to use multiples of 1000
              (S.I.) instead of 1024.  Can also specify custom units e.g.
              --units 3M.

       --userdata user_data
              Specify user data (a word) to be stored with a new region. The
              value is added to any internal auxilliary data (for example,
              group information), and stored with the region in the aux_data
              field provided by the kernel. Whitespace is not permitted.

       -u|--uuid
              Specify the uuid.

       -v|--verbose [-v|--verbose]
              Produce additional output.

COMMANDS         top

       clear device_name [--allprograms|--programid id]
              [--allregions|--regionid id]
              Instructs  the  kernel  to  clear  statistics counters for the
              speficied  regions  (with  the  exception  of   in-flight   IO
              counters).

       create device_name...|file_path...|--alldevices [--areas
              nr_areas|--areasize area_size] [--bounds histogram_boundaries]
              [--filemap] [--follow follow_mode] [--foreground]
              [--nomonitor] [--nogroup] [--precise] [--start start_sector
              --length length|--segments] [--userdata user_data]
              [--programid id]
              Creates one or more new statistics regions  on  the  specified
              device(s).

              The  region  will  span  the  entire device unless --start and
              --length or --segments are  given.  The  --start  an  --length
              options  allow a region of arbitrary length to be placed at an
              arbitrary offset into the device. The --segments option causes
              a   new   region   to  be  created  for  each  target  in  the
              corresponding device-mapper device's table.

              If the --precise option is used the command  will  attempt  to
              create a region using nanosecond precision counters.

              If  --bounds  is given a latency histogram will be tracked for
              the new region. The boundaries of the histogram bins are given
              as  a  comma  separated  list  of  latency values. There is an
              implicit lower bound of zero on the first bin and an  implicit
              upper  bound of infinity (or the configured interval duration)
              on the final bin.

              Latencies are given in nanoseconds. An optional unit suffix of
              ns,  us,  ms,  or  s  may be given after each value to specify
              units of nanoseconds,  microseconds,  miliseconds  or  seconds
              respectively,  so for example, 10ms is equivalent to 10000000.
              Latency values with a precision of less  than  one  milisecond
              can  only  be  used  when  precise  timestamps are enabled: if
              --precise is not given and values less than one milisecond are
              used it will be enabled automatically.

              An  optional  program_id or user_data string may be associated
              with the region. A program_id  may  then  be  used  to  select
              regions for subsequent list, print, and report operations. The
              user_data stores an  arbitrary  string  and  is  not  used  by
              dmstats or the device-mapper kernel statistics subsystem.

              By  default  dmstats  creates  regions  with  a  program_id of
              "dmstats".

              On success the  region_id  of  the  newly  created  region  is
              printed to stdout.

              If  the --filemap option is given with a regular file, or list
              of files, as  the  file_path  argument,  instead  of  creating
              regions with parameters specified on the command line, dmstats
              will open the files located at file_path  and  create  regions
              corresponding  to  the physical extents allocated to the file.
              This can be used to monitor statistics for individual files in
              the  file  system,  for  example, virtual machine images, swap
              areas, or large database files.

              To work with the --filemap option, files must be located on  a
              local  file  system,  backed  by  a device-mapper device, that
              supports physical extent data using the FIEMAP ioctl (Ext4 and
              XFS for e.g.).

              By default regions that map a file are placed into a group and
              the group alias is set to  the  basename  of  the  file.  This
              behaviour  can  be  overridden  with the --alias and --nogroup
              options.

              Creating a group that  maps  a  file  automatically  starts  a
              daemon,  dmfilemapd to monitor the file and update the mapping
              as the extents allocated to the file  change.  This  behaviour
              can be disabled using the --nomonitor option.

              Use  the --group option to only display information for groups
              when listing and reporting.

       delete device_name|--alldevices [--allprograms|--programid id]
              [--allregions|--regionid id]
              Delete  the  specified  statistics  region.  All  counters and
              resources used by the region are released and the region  will
              not  appear in the output of subsequent list, print, or report
              operations.

              All regions registered  on  a  device  may  be  removed  using
              --allregions.

              To  remove  all  regions  on all devices both --allregions and
              --alldevices must be used.

              If a --groupid is given instead of a  --regionid  the  command
              will  attempt  to  delete  the  group  and all regions that it
              contains.

              If a deleted region is the first member of a group of  regions
              the group will also be removed.

       group [device_name|--alldevices] [--alias name] [--regions regions]
              Combine one or more statistics regions on the specified device
              into a group.

              The list of regions to be grouped is specified with  --regions
              and an optional alias may be assigned with --alias. The set of
              regions  is  given  as  a  comma-separated  list   of   region
              identifiers. A continuous range of identifers spanning from R1
              to R2 may be expressed as 'R1-R2'.

              Regions that have a histogram configured can  be  grouped:  in
              this  case  the number of histogram bins and their bounds must
              match exactly.

              On success the group  list  and  newly  created  group_id  are
              printed to stdout.

              The  group metadata is stored with the first (lowest numbered)
              region_id in the group: deleting this region will also  delete
              the  group  and  other group members will be returned to their
              prior state.

       help [-c|-C|--columns]
              Outputs  a  summary  of  the  commands  available,  optionally
              including the list of report fields.

       list [device_name] [--histogram] [--allprograms|--programid id]
              [--units units] [--area] [--region] [--group] [--nosuffix]
              [--notimesuffix] [-v|--verbose]
              List  the  statistics  regions, areas, or groups registered on
              the device.  If the --allprograms switch is given all  regions
              will be listed regardless of region program ID values.

              By  default  only  regions  and  groups  are  included in list
              output. If -v or --verbose  is  given  the  report  will  also
              include a row of information for each configured group and for
              each area contained in each region displayed.

              Regions that contain a single area are by default omitted from
              the  verbose  list since their properties are identical to the
              area that they contain - to view all regions regardless of the
              number  of areas present use --region). To also view the areas
              contained within regions use --area.

              If --histogram is given the report will include the bin  count
              and latency boundary values for any configured histograms.

       print [device_name] [--clear] [--allprograms|--programid id]
              [--allregions|--regionid id]
              Print raw statistics counters for the specified region or  for
              all present regions.

       report [device_name] [--interval seconds] [--count count] [--units
              units] [--histogram] [--allprograms|--programid id]
              [--allregions|--regionid id] [--area] [--region] [--group]
              [-O|--sort sort_fields] [-S|--select selection] [--units
              units] [--nosuffix] [--notimesuffix]
              Start  a  report  for  the specified object or for all present
              objects. If the count argument is specified, the  report  will
              repeat  at  a fixed interval set by the --interval option. The
              default interval is one second.

              If the --allprograms switch is  given,  all  regions  will  be
              listed, regardless of region program ID values.

              If  the  --histogram  is  given  the  report  will include the
              histogram values and latency boundaries.

              If the --relative is used the default histogram field displays
              bin values as a percentage of the total number of I/Os.

              Object  types  (areas,  regions  and groups) to include in the
              report are selected using the --area,  --region,  and  --group
              options.

       ungroup [device_name|--alldevices] [--groupid id]
              Remove an existing group and return all the group's regions to
              their original state.

              The group to be removed is specified using --groupid.

       update_filemap file_path [--groupid id] [--follow follow_mode]
              [--foreground]
              Update  a group of dmstats regions specified by group_id, that
              were previously created with --filemap, either directly, or by
              starting the monitoring daemon, dmfilemapd.

              This  will  add  and  remove regions to reflect changes in the
              allocated extents of the file on-disk, since the time that  it
              was crated or last updated.

              Use   of  this  command  is  not  normally  needed  since  the
              dmfilemapd daemon will automatically  monitor  filemap  groups
              and perform these updates when required.

              If  a  filemapped  group  was created with --nomonitor, or the
              daemon has been killed, the  update_filemap  can  be  used  to
              manually force an update or start a new daemon.

              Use  --nomonitor to force a direct update and disable starting
              the monitoring daemon.

REGIONS, AREAS, AND GROUPS         top

       The device-mapper statistics facility allows separate performance
       counters to be maintained for arbitrary regions of devices. A region
       may span any range: from a single sector to the whole device. A
       region may be further sub-divided into a number of distinct areas
       (one or more), each with its own counter set. In this case a summary
       value for the entire region is also available for use in reports.

       In addition, one or more regions on one device can be combined into a
       statistics group. Groups allow several regions to be aggregated and
       reported as a single entity; counters for all regions and areas are
       summed and used to report totals for all group members. Groups also
       permit the assignment of an optional alias, allowing meaningful names
       to be associated with sets of regions.

       The group metadata is stored with the first (lowest numbered)
       region_id in the group: deleting this region will also delete the
       group and other group members will be returned to their prior state.

       By default new regions span the entire device. The --start and
       --length options allows a region of any size to be placed at any
       location on the device.

       Using offsets it is possible to create regions that map individual
       objects within a block device (for example: partitions, files in a
       file system, or stripes or other structures in a RAID volume). Groups
       allow several non-contiguous regions to be assembled together for
       reporting and data aggregation.

       A region may be either divided into the specified number of equal-
       sized areas, or into areas of the given size by specifying one of
       --areas or --areasize when creating a region with the create command.
       Depending on the size of the areas and the device region the final
       area within the region may be smaller than requested.

       Region identifiers

       Each region is assigned an identifier when it is created that is used
       to reference the region in subsequent operations. Region identifiers
       are unique within a given device (including across different
       program_id values).

       Depending on the sequence of create and delete operations, gaps may
       exist in the sequence of region_id values for a particular device.

       The region_id should be treated as an opaque identifier used to
       reference the region.

       Group identifiers

       Groups are also assigned an integer identifier at creation time; like
       region identifiers, group identifiers are unique within the
       containing device.

       The group_id should be treated as an opaque identifier used to
       reference the group.

FILE MAPPING         top

       Using --filemap, it is possible to create regions that correspond to
       the extents of a file in the file system. This allows IO statistics
       to be monitored on a per-file basis, for example to observe large
       database files, virtual machine images, or other files of interest.

       To be able to use file mapping, the file must be backed by a device-
       mapper device, and in a file system that supports the FIEMAP ioctl
       (and which returns data describing the physical location of extents).
       This currently includes xfs(5) and ext4(5).

       By default the regions making up a file are placed together in a
       group, and the group alias is set to the basename(3) of the file.
       This allows statistics to be reported for the file as a whole,
       aggregating values for the regions making up the group. To see only
       the whole file (group) when using the list and report commands, use
       --group.

       Since it is possible for the file to change after the initial group
       of regions is created, the update_filemap command, and dmfilemapd
       daemon are provided to update file mapped groups either manually or
       automatically.

       File follow modes

       The file map monitoring daemon can monitor files in two distinct
       ways: follow-inode mode, and follow-path mode.

       The mode affects the behaviour of the daemon when a file under
       monitoring is renamed or unlinked, and the conditions which cause the
       daemon to terminate.

       If follow-inode mode is used, the daemon will hold the file open, and
       continue to update regions from the same file descriptor. This means
       that the mapping will follow rename, move (within the same file
       system), and unlink operations. This mode is useful if the file is
       expected to be moved, renamed, or unlinked while it is being
       monitored.

       In follow-inode mode, the daemon will exit once it detects that the
       file has been unlinked and it is the last holder of a reference to
       it.

       If follow-path is used, the daemon will re-open the provided path on
       each monitoring iteration. This means that the group will be updated
       to reflect a new file being moved to the same path as the original
       file. This mode is useful for files that are expected to be updated
       via unlink and rename.

       In follow-path mode, the daemon will exit if the file is removed and
       not replaced within a brief tolerance interval (one second).

       To stop the daemon, delete the group containing the mapped regions:
       the daemon will automatically shut down.

       The daemon can also be safely killed at any time and the group kept:
       if the file is still being allocated the mapping will become
       progressively out-of-date as extents are added and removed (in this
       case the daemon can be re-started or the group updated manually with
       the update_filemap command).

       See the create command and --filemap, --follow, and --nomonitor
       options for further information.

       Limitations

       The daemon attempts to maintain good synchronisation between the file
       extents and the regions contained in the group, however, since it can
       only react to new allocations once they have been written, there are
       inevitably some IO events that cannot be counted when a file is
       growing, particularly if the file is being extended by a single
       thread writing beyond end-of-file (for example, the dd program).

       There is a further loss of events in that there is currently no way
       to atomically resize a dmstats region and preserve its current
       counter values. This affects files when they grow by extending the
       final extent, rather than allocating a new extent: any events that
       had accumulated in the region between any prior operation and the
       resize are lost.

       File mapping is currently most effective in cases where the majority
       of IO does not trigger extent allocation. Future updates may address
       these limitations when kernel support is available.

REPORT FIELDS         top

       The dmstats report provides several types of field that may be added
       to the default field set, or used to create custom reports.

       All performance counters and metrics are calculated per-area.

   Derived metrics
       A number of metrics fields are included that provide high level
       performance indicators. These are based on the fields provided by the
       conventional Linux iostat program and are derived from the basic
       counter values provided by the kernel for each area.

       reads_merged_per_sec
              Reads merged per second.

       writes_merged_per_sec
              Writes merged per second.

       reads_per_sec
              Reads completed per second.

       writes_per_sec
              Writes completed per second.

       read_size_per_sec
              Size of data read per second.

       write_size_per_sec
              Size of data written per second.

       avg_request_size
              Average request size.

       queue_size
              Average queue size.

       await  The average wait time for read and write operations.

       r_await
              The average wait time for read operations.

       w_await
              The average wait time for write operations.

       throughput
              The device throughput in operations per second.

       service_time
              The average service time (in milliseconds) for operations
              issued to the device.

       util   Percentage of CPU time during which I/O requests were issued
              to the device (bandwidth utilization for the device). Device
              saturation occurs when this value is close to 100%.

   Group, region and area meta fields
       Meta fields provide information about the groups, regions, or areas
       that the statistics values relate to. This includes the region and
       area identifier, start, length, and counts, as well as the program ID
       and user data values.

       region_id
              Region identifier. This is a non-negative integer returned by
              the kernel when a statistics region is created.

       region_start
              The region start location. Display units are selected by the
              --units option.

       region_len
              The length of the region. Display units are selected by the
              --units option.

       area_id
              Area identifier. Area identifiers are assigned by the device-
              mapper statistics library and uniquely identify each area
              within a region. Each ID corresponds to a distinct set of
              performance counters for that area of the statistics region.
              Area identifiers are always monotonically increasing within a
              region so that higher ID values correspond to greater sector
              addresses within the area and no gaps in the sequence of
              identifiers exist.

       area_start
              The area start location. Display units are selected by the
              --units option.

       area_len
              The length of the area. Display units are selected by the
              --units option.

       area_count
              The number of areas in this region.

       program_id
              The program ID value associated with this region.

       user_data
              The user data value associated with this region.

       group_id
              Group identifier. This is a non-negative integer returned by
              the dmstats group command when a statistics group is created.

       interval_ns
              The estimated interval over which the current counter values
              have accumulated. The value is reported as an interger
              expressed in units of nanoseconds.

       interval
              The estimated interval over which the current counter values
              have accumulated. The value is reported as a real number in
              units of seconds.

   Basic counters
       Basic counters provide access to the raw counter data from the
       kernel, allowing further processing to be carried out by another
       program.

       The kernel provides thirteen separate counters for each statistics
       area. The first eleven of these match the counters provided in
       /proc/diskstats or /sys/block/*/*/stat. The final pair provide
       separate counters for read and write time.

       read_count
              Count of reads completed this interval.

       reads_merged_count
              Count of reads merged this interval.

       read_sector_count
              Count of 512 byte sectors read this interval.

       read_time
              Accumulated duration of all read requests (ns).

       write_count
              Count of writes completed this interval.

       writes_merged_count
              Count of writes merged this interval.

       write_sector_count
              Count of 512 byte sectors written this interval.

       write_time
              Accumulated duration of all write requests (ns).

       in_progress_count
              Count of requests currently in progress.

       io_ticks
              Nanoseconds spent servicing requests.

       queue_ticks
              This field is incremented at each I/O start, I/O completion,
              I/O merge, or read of these stats by the number of I/Os in
              progress multiplied by the number of milliseconds spent doing
              I/O since the last update of this field.  This can provide an
              easy measure of both I/O completion time and the backlog that
              may be accumulating.

       read_ticks
              Nanoseconds spent servicing reads.

       write_ticks
              Nanoseconds spent servicing writes.

   Histogram fields
       Histograms measure the frequency distribution of user specified I/O
       latency intervals. Histogram bin boundaries are specified when a
       region is created.

       A brief representation of the histogram values and latency intervals
       can be included in the report using these fields.

       hist_count
              A list of the histogram counts for the current statistics area
              in order of ascending latency value. Each value represents the
              number of I/Os with latency times falling into that bin's time
              range during the sample period.

       hist_count_bounds
              A list of the histogram counts for the current statistics area
              in order of ascending latency value including bin boundaries:
              each count is prefixed by the lower bound of the corresponding
              histogram bin.

       hist_count_ranges
              A list of the histogram counts for the current statistics area
              in order of ascending latency value including bin boundaries:
              each count is prefixed by both the lower and upper bounds of
              the corresponding histogram bin.

       hist_percent
              A list of the relative histogram values for the current
              statistics area in order of ascending latency value, expressed
              as a percentage. Each value represents the proportion of I/Os
              with latency times falling into that bin's time range during
              the sample period.

       hist_percent_bounds
              A list of the relative histogram values for the current
              statistics area in order of ascending latency value, expressed
              as a percentage and including bin boundaries. Each value
              represents the proportion of I/Os with latency times falling
              into that bin's time range during the sample period and is
              prefixed with the corresponding bin's lower bound.

       hist_percent_ranges
              A list of the relative histogram values for the current
              statistics area in order of ascending latency value, expressed
              as a percentage and including bin boundaries. Each value
              represents the proportion of I/Os with latency times falling
              into that bin's time range during the sample period and is
              prefixed with the corresponding bin's lower and upper bounds.

       hist_bounds
              A list of the histogram boundary values for the current
              statistics area in order of ascending latency value.  The
              values are expressed in whole units of seconds, miliseconds,
              microseconds or nanoseconds with a suffix indicating the unit.

       hist_ranges
              A list of the histogram bin ranges for the current statistics
              area in order of ascending latency value.  The values are
              expressed as "LOWER-UPPER" in whole units of seconds,
              miliseconds, microseconds or nanoseconds with a suffix
              indicating the unit.

       hist_bins
              The number of latency histogram bins configured for the area.

EXAMPLES         top

       Create a whole-device region with one area on vg00/lvol1
       # dmstats create vg00/lvol1
       vg00/lvol1: Created new region with 1 area(s) as region ID 0

       Create a 32M region 1G into device d0
       # dmstats create --start 1G --length 32M d0
       d0: Created new region with 1 area(s) as region ID 0

       Create a whole-device region with 8 areas on every device
       # dmstats create --areas 8
       vg00-lvol1: Created new region with 8 area(s) as region ID 0
       vg00-lvol2: Created new region with 8 area(s) as region ID 0
       vg00-lvol3: Created new region with 8 area(s) as region ID 0
       vg01-lvol0: Created new region with 8 area(s) as region ID 2
       vg01-lvol1: Created new region with 8 area(s) as region ID 0
       vg00-lvol2: Created new region with 8 area(s) as region ID 1

       Delete all regions on all devices
       # dmstats delete --alldevices --allregions

       Create a whole-device region with areas 10GiB in size on vg00/lvol1
       using dmsetup
       # dmsetup stats create --areasize 10G vg00/lvol1
       vg00-lvol1: Created new region with 5 area(s) as region ID 1

       Create a 1GiB region with 16 areas at the start of vg00/lvol1
       # dmstats create --start 0 --len 1G --areas=16 vg00/lvol1
       vg00-lvol1: Created new region with 16 area(s) as region ID 0

       List the statistics regions registered on vg00/lvol1
       # dmstats list vg00/lvol1
       Name             RgID  RStart RSize  #Areas ASize  ProgID
       vg00-lvol1           0      0 61.00g      1 61.00g dmstats
       vg00-lvol1           1 61.00g 19.20g      1 19.20g dmstats
       vg00-lvol1           2 80.20g  2.14g      1  2.14g dmstats

       Display five statistics reports for vg00/lvol1 at an interval of one
       second
       # dmstats report --interval 1 --count 5 vg00/lvol1
       # dmstats report
       Name             RgID  ArID  AStart ASize  RRqM/s   WRqM/s   R/s
       W/s    RSz/s WSz/s   AvRqSz  QSize Util%      AWait RdAWa WrAWa
       vg_hex-lv_home       0     0      0 61.00g     0.00     0.00  0.00
       218.00     0   1.04m   4.50k  2.97      81.70 13.62  0.00 13.62
       vg_hex-lv_home       1     0 61.00g 19.20g     0.00     0.00  0.00
       5.00     0 548.00k 109.50k  0.14      11.00 27.40  0.00 27.40
       vg_hex-lv_home       2     0 80.20g  2.14g     0.00     0.00  0.00
       14.00     0   1.15m  84.00k  0.39      18.70 27.71  0.00 27.71

       Create one region for reach target contained in device vg00/lvol1
       # dmstats create --segments vg00/lvol1
       vg00-lvol1: Created new region with 1 area(s) as region ID 0
       vg00-lvol1: Created new region with 1 area(s) as region ID 1
       vg00-lvol1: Created new region with 1 area(s) as region ID 2

       Create regions mapping each file in the directory images/ and place
       them into separate groups, each named after the corresponding file
       # dmstats create --filemap images/*
       images/vm1.qcow2: Created new group with 87 region(s) as group ID 0.
       images/vm1-1.qcow2: Created new group with 8 region(s) as group ID
       87.
       images/vm2.qcow2: Created new group with 11 region(s) as group ID 95.
       images/vm2-1.qcow2: Created new group with 1454 region(s) as group ID
       106.
       images/vm3.img: Created new group with 2 region(s) as group ID 1560.

       Print raw counters for region 4 on device d0
       # dmstats print --regionid 4 d0
       2097152+65536 0 0 0 0 29 0 264 701 0 41 701 0 41

AUTHORS         top

       Bryn M. Reeves <bmr@redhat.com>

SEE ALSO         top

       dmsetup(8)

       LVM2 resource page: https://www.sourceware.org/lvm2/
       Device-mapper resource page: http://sources.redhat.com/dm/

       Device-mapper statistics kernel documentation
       Documentation/device-mapper/statistics.txt

COLOPHON         top

       This page is part of the lvm2 (Logical Volume Manager 2) project.
       Information about the project can be found at 
       ⟨http://www.sourceware.org/lvm2/⟩.  If you have a bug report for this
       manual page, send it to linux-lvm@redhat.com.  This page was obtained
       from the project's upstream Git repository 
       ⟨git://sourceware.org/git/lvm2.git⟩ on 2017-09-15.  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

Linux                            Jun 23 2016                      DMSTATS(8)

Pages that refer to this page: pmdadm(1)dmsetup(8)lvm(8)lvmsadc(8)lvmsar(8)