.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 .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 [[ \-\-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 [ \-\-units .IR units ] .RB [ \-\-nosuffix ] .RB [ \-\-nosuffix ] .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 [ \-\-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 ] .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 \-\-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 .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 .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 \-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 [[ \-\-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. 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 "DMSTATS1". 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 [ \-\-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. .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. .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 rrqm .br Read requests merged per second. .HP .B wrqm .br Write requests merged per second. .HP .B rs .br Read requests per second. .HP .B ws .br Write requests per second. .HP .B rsec .br Sectors read per second. .HP .B wsec .br Sectors written per second. .HP .B arqsz .br The average size of requests submitted to the area. .HP .B qusz .br The average queue length. .HP .B await .br The average wait time for read and write requests. .HP .B r_await .br The average wait time for read requests. .HP .B w_await .br The average wait time for write requests. .HP .B tput .br The device throughput in requests per second. .HP .B svctm .br The average service time (in milliseconds) for I/O requests that were 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 sector in units of 512 byte sectors. .HP .B region_len .br The length of the region in units of 512 byte sectors. .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 region and no gaps in the sequence of identifiers exist. Sorting a report by device, region start, and area ID (the default) will then produce rows in order of ascending region and area address. .HP .B area_start .br The area start sector in units of 512 byte sectors. .HP .B area_len .br The length of the area in units of 512 byte sectors. .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 vaulue 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 reads .br The number of reads successfully completed this interval. .HP .B read_merges .br The number of read requests merged this interval. This field is incremented every time a pair of requests are merged to create a single request to be issued to the device. .HP .B read_sectors .br The number of 512 byte sectors read this interval. .HP .B read_nsecs .br The number of nanoseconds spent reading during this interval. .HP .B writes .br The number of writes successfully completed this interval. .HP .B write_merges .br The number of write requests merged this interval. This field is incremented every time a pair of requests are merged to create a single request to be issued to the device. .HP .B write_sectors .br The number of 512 byte sectors written this interval. .HP .B write_nsecs .br The number of nanoseconds spent writing during this interval. .HP .B in_progress .br The number of reads and writes currently in progress. .HP .B io_nsecs .br The number of nanoseconds spent reading and writing. .HP .B weighted_io_nsecs .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. .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 Created new region with 1 area(s) as region ID 0 .br Created new region with 1 area(s) as region ID 1 .br Created new region with 1 area(s) as region ID 2 .br .br Print raw counters for region 4 on device d0 .br .br # dmstats print --regionid 4 d0 .br 2097152+65536 0 0 0 0 29 0 264 701 0 41 701 0 41 .br .br .SH AUTHORS Bryn M. Reeves .SH SEE ALSO LVM2 resource page https://www.sourceware.org/lvm2/ .br Device-mapper resource page: http://sources.redhat.com/dm/ .br Device-mapper statistics kernel documentation .br Documentation/device-mapper/statistics.txt