.TH DMSTATS 8 "Jul 25 2015" "Linux" "MAINTENANCE COMMANDS"
.SH NAME
dmstats \(em device-mapper statistics management
.SH SYNOPSIS
.ad l
.B dmsetup stats
.I command
.RB [ options ]
.br

.B dmstats <command>
.RB [[
.IR device_name ]
.RB |[ \-\-uuid
.IR uuid ]
.RB |[ \-\-major
.IR major
.RB \-\-minor
.IR minor ]]
.br

.B dmstats clear
.I device_name
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.br
.B dmstats create
.I device_name
.RB [ \-\-alldevices ]
.RB [[ \-\-areas
.IR nr_areas ]
.RB |[ \-\-areasize
.IR area_size ]]
.RB [ \-\-bounds
.IR histogram_boundaries ]
.RB [ \-\-precise ]
.RB [[ \-\-start
.IR start_sector ]
.RB [ \-\-length
.IR length ]
.RB |[ \-\-segments ]]
.RB [ \-\-auxdata
.IR data ]
.RB [ \-\-programid
.IR id ]
.br
.B dmstats delete
.I device_name
.RB [ \-\-alldevices ]
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.br
.B dmstats help
.RB [ \-c | \-C | \-\-columns ]
.br
.B dmstats list
.RI [ device_name ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.RB [ \-\-histogram ]
.RB [ \-\-units
.IR units ]
.RB [ \-\-nosuffix ]
.RB [ \-\-notimesuffix ]
.RB [ \-v | \-\-verbose \ [ \-v | \-\-verbose ]
.br
.B dmstats print
.RI [ device_name ]
.RB [ \-\-clear ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.br
.B dmstats report
.RI [ device_name ]
.RB [ \-\-interval
.IR seconds ]
.RB [ \-\-count
.IR count ]
.RB [ \-\-units
.IR units ]
.RB [ \-\-histogram ]
.RB [ \-\-allprograms ]
.RB [ \-\-programid
.IR id ]
.RB [ \-\-regionid
.IR id ]
.RB [ \-O | \-\-sort
.IR sort_fields ]
.RB [ \-S | \-\-select
.IR Selection ]
.RB [ \-\-units
.IR units ]
.RB [ \-\-nosuffix ]
.RB [ \-\-notimesuffix ]
.br
.ad b
.SH 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 behaviour.

When the program is run using the 'dmstats' alias, the command
\fBmust\fP be the first argument and any switches and options should be
specified following the command itself. This limitation is not present
when run as 'dmsetup stats'.

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

.SH OPTIONS
.TP
.B \-\-alldevices
If no device arguments are given allow operation on all devices when
creating or deleting regions.
.TP
.B \-\-allprograms
Include regions from all program IDs for list and report operations.
.TP
.B \-\-allregions
Include all present regions for commands that normally accept a single
region identifier.
.TP
.B \-\-areas \fInr_areas
Specify the number of statistics areas to create within a new region.
.TP
.B \-\-areasize \fIarea_size
Specify the size of areas into which a new region should be divided. An
optional suffix selects units of bBsSkKmMgGtTpPeE: (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.
.TP
.B \-\-auxdata \fIaux_data
Specify auxilliary data (a string) to be stored with a new region.
.TP
.B \-\-clear
When printing statistics counters, also atomically reset them to zero.
.TP
.B \-\-count \fIcount
Specify the iteration count for repeating reports. If the count
argument is zero reports will continue to repeat until interrupted.
.TP
.B \-\-bounds \fIhistogram_boundaries
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.
.TP
.B \-\-histogram
When used with the \fBreport\fP and \fBlist\fP commands select default
fields that emphasize latency histogram data.
.TP
.B \-\-interval \fIseconds
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.
.TP
.B \-\-length \fIlength
Specify the length of a new statistics region in sectors. An optional
suffix selects units of bBsSkKmMgGtTpPeE: (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.
.TP
.BR \-j | \-\-major\ \fImajor
Specify the major number.
.TP
.BR \-m | \-\-minor\ \fIminor
Specify the minor number.
.TP
.B \-\-nosuffix
Suppress the suffix on output sizes.  Use with \fB\-\-units\fP
(except h and H) if processing the output.
.TP
.B \-\-notimesuffix
Suppress the suffix on output time values. Histogram boundary values
will be reported in units of nanoseconds.
.TP
.BR \-o | \-\-options
Specify which report fields to display.
.TP
.BR \-O | \-\-sort\ \fIsort_fields
Sort output according to the list of fields given. Precede any
sort_field with - for a reverse sort on that column.
.TP
.BR \-\-precise
Attempt to use nanosecond precision counters when creating new
statistics regions.
.TP
.B \-\-programid \fIid
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".
.TP
.BR \-\-regionid \fIid
Specify the region to operate on.
.TP
.BR \-\-relative
If displaying the histogram report show relative (percentage) values
instead of absolute counts.
.TP
.BR \-S | \-\-select \ \fIselection
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.
.TP
.B \-\-start \fIstart
Specify the start offset of a new statistics region in sectors. An
optional suffix selects units of bBsSkKmMgGtTpPeE: (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.
.TP
.B \-\-segments
Create a new statistics region for each target contained in the target
device. This causes a separate region to be allocated for each segment
of the device.
.TP
.BR \-\-units \ hHbBsSkKmMgGtTpPeE
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. \fB\-\-units 3M\fP
.TP
.BR \-u | \-\-uuid
Specify the uuid.
.TP
.BR \-v | \-\-verbose \ [ \-v | \-\-verbose ]
Produce additional output.
.br
.SH COMMANDS
.TP
.B clear
.I device_name
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.br
Instructs the kernel to clear statistics counters for the speficied
regions (with the exception of in-flight IO counters).
.br
.TP
.B create
.I device_name
.RB [ \-\-areas
.IR nr_areas ]
.RB [ \-\-areasize
.IR area_size ]
.RB [ --bounds
.IR histogram_boundaries ]
.RB [ \-\-precise ]
.RB [[ \-\-start
.IR start_sector ]
.RB [ \-\-length
.IR length ]
.RB |[ \-\-segments ]]
.RB [ \-\-auxdata
.IR data ]
.RB [ \-\-programid
.IR id ]
.br
Creates one or more new statistics regions on the specified device(s).

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

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

If \fB--bounds\fP 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
\fB\-\-precise\fP is not given and values less than one milisecond are
used it will be enabled automatically.

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

By default dmstats creates regions with a \fBprogram_id\fP of
"dmstats".

On success the \fBregion_id\fP of the newly created region is printed to
stdout.
.br
.TP
.B delete
.I [ device_name ]
.RB [ \-\-alldevices ]
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.br
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
\fB\-\-allregions\fP.

To remove all regions on all devices both \fB--allregions\fP and
\fB\-\-alldevices\fP must be used.
.br
.TP
.B help
.RB [ \-c | \-C | \-\-columns ]
.br
Outputs a summary of the commands available, optionally including
the list of report fields.
.br
.TP
.B list
.RI [ device_name ]
.RB [ \-\-histogram ]
.RB [ \-\-allprograms ]
.RB [ \-\-programid
.RB [ \-v | \-\-verbose \ [ \-v | \-\-verbose ]]
.IR id ]
.br
List the statistics regions registered on the device. If the
\fB\-\-allprograms\fP switch is given all regions will be listed
regardless of region program ID values.

If \fB\-v\fP or \fB\-\-verbose\fP is given the report will include
a row of information for each area contained in each region displayed.

If \fB\-\-histogram\fP is given the report will include the bin count
and latency boundary values for any configured histograms.
.br
.TP
.B print
.RB [ \-\-clear ]
.IR
.RB [ \-\-allregions
.RB | \-\-regionid
.IR id ]
.RB [ \-\-allprograms
.RB | \-\-programid
.IR id ]
.br
Print raw statistics counters for the specified region or for all
present regions.
.br
.TP
.B report
.RB [ \-\-allprograms ]
.RB [ \-\-interval
.IR seconds ]
.RB [ \-\-count
.IR count ]
.RB [ \-\-units
.IR unit ]
.RB [ \-\-regionid
.IR id ]
.RB [ \-\-programid
.IR id ]
.RB [ \-O | \-\-sort
.IR sort_fields ]
.RB [ \-S | \-\-select
.IR Selection ]
.RB [ \-\-units
.IR units ]
.br
Start a report for the specified region or for all present regions. If
the count argument is specified, the report will repeat at a fixed
interval set by the \fB\-\-interval\fP option. The default interval is
one second.

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

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

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

.br
.SH REGIONS AND AREAS
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.

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

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
\fB\-\-areas\fP or \fB\-\-areasize\fP when creating a region with the
\fBcreate\fP command. Depending on the size of the areas and the device
region the final area within the region may be smaller than requested.

.SS 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 \fBprogram_id\fP
values).
.br
Depending on the sequence of create and delete operations, gaps may
exist in the sequence of \fBregion_id\fP values for a particular device.

.SH 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.
.br
All performance counters and metrics are calculated per-area.
.br
.SS 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.
.br
.HP
.B reads_merged_per_sec
.br
Reads merged per second.
.HP
.B writes_merged_per_sec
.br
Writes merged per second.
.HP
.B reads_per_sec
.br
Reads completed per second.
.HP
.B writes_per_sec
.br
Writes completed per second.
.HP
.B read_size_per_sec
.br
Size of data read per second.
.HP
.B write_size_per_sec
.br
Size of data written per second.
.HP
.B avg_request_size
.br
Average request size.
.HP
.B queue_size
.br
Average queue size.
.HP
.B await
.br
The average wait time for read and write operations.
.HP
.B r_await
.br
The average wait time for read operations.
.HP
.B w_await
.br
The average wait time for write operations.
.HP
.B throughput
.br
The device throughput in operations per second.
.HP
.B service_time
.br
The  average  service  time  (in milliseconds) for operations issued
to the device.
.HP
.B util
.br
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%.
.br
.SS Region and area meta fields
Meta fields provide information about the region or area that the
statistics values relate to. This includes the region and area
identifier, start, length, and counts, as well as the program ID and
auxiliary data values.
.br
.HP
.B region_id
.br
Region identifier. This is a non-negative integer returned by the kernel
when a statistics region is created.
.HP
.B region_start
.br
.br
The region start location. Display units are selected by the
\fB--units\fP option.
.HP
.B region_len
.br
The length of the region. Display units are selected by the
\fB--units\fP option.
.HP
.B area_id
.br
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.
.HP
.B area_start
.br
The area start location. Display units are selected by the
\fB--units\fP option.
.HP
.B area_len
.br
The length of the area. Display units are selected by the
\fB--units\fP option.
.HP
.B area_count
.br
The number of areas in this region.
.HP
.B program_id
.br
The program ID value associated with this region.
.HP
.B aux_data
.br
The auxiliary data value associated with this region.
.br
.HP
.B interval_ns
.br
The estimated interval over which the current counter values have
accumulated. The value is reported as an interger expressed in units
of nanoseconds.
.br
.HP
.B interval
.br
The estimated interval over which the current counter values have
accumulated. The value is reported as a real number in units of
seconds.
.br
.SS 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.
.P
.HP
.B read_count
.br
Count of reads completed this interval.
.HP
.B reads_merged_count
.br
Count of reads merged this interval.
.HP
.B read_sector_count
.br
Count of 512 byte sectors read this interval.
.HP
.B read_time
.br
Accumulated duration of all read requests (ns).
.HP
.B write_count
.br
Count of writes completed this interval.
.HP
.B writes_merged_count
.br
Count of writes merged this interval.
.HP
.B write_sector_count
.br
Count of 512 byte sectors written this interval.
.HP
.B write_nsecs
.br
Accumulated duration of all write requests (ns).
.HP
.B in_progress_count
.br
Count of requests currently in progress.
.HP
.B io_ticks
.br
Nanoseconds spent servicing requests.
.HP
.B queue_ticks
.br
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.
.HP
.B read_ticks
.br
Nanoseconds spent servicing reads.
.HP
.B write_ticks
.br
Nanoseconds spent servicing writes.
.br
.SS 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.
.P
.HP
.B hist_count
.br
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.
.HP
.B hist_count_bounds
.br
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.
.HP
.B hist_count_ranges
.br
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.
.HP
.B hist_percent
.br
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.
.HP
.B hist_percent_bounds
.br
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.
.HP
.B hist_percent_ranges
.br
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.
.HP
.B hist_bounds
.br
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.
.HP
.B hist_ranges
.br
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.
.HP
.B hist_bins
.br
The number of latency histogram bins configured for the area.
.br
.br
.P
.SH EXAMPLES
Create a whole-device region with one area on vg00/lvol1
.br
.br
# dmstats create vg00/lvol1
.br
vg00/lvol1: Created new region with 1 area(s) as region ID 0
.br
.br


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


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

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

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

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

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

Display five statistics reports for vg00/lvol1 at an interval of one second
.br
.br
# dmstats report --interval 1 --count 5 vg00/lvol1
.br
# dmstats report
.br
Name             RgID  ArID  AStart ASize  RRqM/s   WRqM/s   R/s   W/s    RSz/s WSz/s   AvRqSz  QSize Util%      AWait RdAWa WrAWa
.br
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
.br
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
.br
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
.br
.br

Create one region for reach target contained in device vg00/lvol1
.br
.br
# dmstats create --segments vg00/lvol1
.br
vg00-lvol1: Created new region with 1 area(s) as region ID 0
.br
vg00-lvol1: Created new region with 1 area(s) as region ID 1
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vg00-lvol1: Created new region with 1 area(s) as region ID 2
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Print raw counters for region 4 on device d0
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# dmstats print --regionid 4 d0
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2097152+65536 0 0 0 0 29 0 264 701 0 41 701 0 41
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.SH AUTHORS
Bryn M. Reeves <bmr@redhat.com>

.SH SEE ALSO
LVM2 resource page https://www.sourceware.org/lvm2/
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Device-mapper resource page: http://sources.redhat.com/dm/
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Device-mapper statistics kernel documentation
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   Documentation/device-mapper/statistics.txt