dmstats(8) - phpMan

DMSTATS(8) MAINTENANCE COMMANDS DMSTATS(8)

NAME
dmstats -- device-mapper statistics management

SYNOPSIS
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] [--his-
togram] [--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
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 be-
haviour.

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
--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 iden-
tifier.

--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 mon-
itor 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 fol-
low 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 monitor-
ing 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 cre-
ate a group or set an alias.

--nosuffix
Suppress the suffix on output sizes. Use with --units (except h and H) if process-
ing 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-man-
aged 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
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|--seg-
ments] [--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, milisec-
onds 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 mon-
itor 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 pro-
gram 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] [--nosuf-
fix] [--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 per-
centage 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 cre-
ated 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 auto-
matically 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 dae-
mon.

REGIONS, AREAS, AND GROUPS
The device-mapper statistics facility allows separate performance counters to be main-
tained 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
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 inter-
est.

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 physi-
cal 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 iter-
ation. 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 auto-
matically 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 infor-
mation.

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 trig-
ger extent allocation. Future updates may address these limitations when kernel support is
available.

REPORT FIELDS
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 (band-
width 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 com-
mand 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 millisec-
onds 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 ascend-
ing 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 ascend-
ing 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 ascend-
ing 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 pro-
portion 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
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
Bryn M. Reeves <bmr AT redhat.com>