dmstats(8)
NAME
dmstats --- device-mapper statistics management
SYNOPSIS
dmsetup stats command [options]
dmstats command [device_name |--uuid uuid|--major major --minor minor]
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] [--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] [--alias name] [--alldevices] [--regions
regions]
dmstats help [-c|-C|--columns]
dmstats list [device_name] [--histogram] [--allprograms|--programid id]
[--units units] [--area] [--region] [--group] [--nosuffix]
[--notimesuffix] [-v|--verbose[-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]
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 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 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).
--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
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] [--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.
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] [--alias name] [--alldevices] [--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[-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.
REGIONS, AREAS, AND GROUPS
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.
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 (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_nsecs
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
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@redhat.com>
SEE ALSO
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
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