dmstats(8) — Linux manual page

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, see ⟨https://github.com/lvmteam/lvm2/issues⟩.
       This page was obtained from the tarball
       https://github.com/lvmteam/lvm2/archive/refs/tags/v2_03_11.tar.gz
       fetched from ⟨https://github.com/lvmteam/lvm2/releases⟩ on
       2021-04-01.  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)