DMSTATS(8) (MAINTENANCE COMMANDS) (NAME) dmstats - (Device-Mapper) (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] [--nogroup] [--nomonitor] [--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] [--allprograms|--programid id] [--area] [--group] [--region] [--histogram] [--nosuffix] [--notimesuffix] [--units units] dmstats print [device_name] [--clear] [--allprograms|--programid id] [--allregions|--regionid id] dmstats report [device_name] [--interval seconds] [--count count] [--units units] [--allprograms|--programid id] [--allregions| --regionid id] [--area] [--group] [--region] [--histogram] [--nosuffix] [--notimesuffix] [--units units] [-O|--sort sort_fields] [-S|--select selection] dmstats ungroup [device_name|--alldevices] [--groupid id] dmstats update_filemap file_path [--follow follow_mode] [--foreground] [--groupid id] [--nomonitor] (DESCRIPTION) dmstats / (device-mapper) . . dmstats command () . device_name ( ) uuid major minor . . dmstats . create delete --alldevices . (OPTIONS) --alias name (alias) . --alldevices . --allprograms (program ID) . --allregions . --area (area) . --areas nr_areas . --areasize area_size[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E] . : (b) (s) (k) (m) (g) (t) (p) (e) . (S.I.) . --bounds histogram_boundaries[ns|us|ms|s] . . ns us ms s . --clear . --count count . . --group (group) . --filemap file_path () . --follow follow_mode dmfilemapd(8) . : (unlink) . follow_mode "inode" inode "path" (follow-path). follow-inode . ( ) unlink . unlink . follow-inode unlink . follow-path . . unlink rename . follow-path . . --foreground dmfilemapd(8) . dmstats . --groupid id . --histogram report list . --interval seconds . --interval --count . --length length[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E] . : (b) (s) (k) (m) (g) (t) (p) (e) . (S.I.) . -j|--major major major . -m|--minor minor minor . --nogroup . --nomonitor dmfilemapd(8) . dmfilemapd(8) . update_filemap . --nosuffix . --units ( h H) . --notimesuffix . . -o|--options . --precise . --programid id (program ID) . . . dmstats "dmstats" . --region (region) . --regionid id . --regions region_list . . : '1-10'. --relative () . --segments create (target) () . (segment) . --nogroup . --alias . -S|--select selection selection . "selected" (-o selected) selection . . -O|--sort sort_fields . . --start start[b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E] . : (b) (s) (k) (m) (g) (t) (p) (e) . (S.I.) . --units [units][h|H|b|B|s|S|k|K|m|M|g|G|t|T|p|P|e|E] . : (h) (human-readable) (b) (s) (k) (m) (g) (t) (p) (e) . (S.I.) . --units 3M. --userdata user_data ( ) . ( ) aux_data . (whitespace) . -u|--uuid uuid . -v|--verbose [-v|--verbose] . (COMMANDS) clear device_name [--allprograms|--programid id] [--allregions| --regionid id] ( / [in-flight IO]). create device_name ...|file_path ...|--alldevices [--areas nr_areas| --areasize area_size] [--bounds histogram_boundaries] [--filemap] [--follow follow_mode] [--foreground] [--nogroup] [--nomonitor] [--precise] [--start start_sector --length length| --segments] [--userdata user_data] [--programid id] () . --start --length --segments . --start --length . --segments . --precise . --bounds . (bins) . ( ) . . ns us ms s 10 ms 10,000,000 . : --precise . program_id user_data . program_id list print report . user_data dmstats . dmstats program_id "dmstats" . region_id stdout . --filemap file_path dmstats file_path . swap . --filemap ioctl FIEMAP ( Ext4 XFS). (basename) . --alias --nogroup . dmfilemapd(8) . --nomonitor . --group . delete device_name|--alldevices [--allprograms|--programid id] [--allregions|--regionid id] . list print report . --allregions . --allregions --alldevices . --groupid --regionid . . group [device_name|--alldevices] [--alias name] [--regions regions] . --regions --alias . . R1 R2 . : . group_id stdout . ( ) region_id : . help [-c|-C|--columns] . list [device_name] [--allprograms|--programid id] [--area] [--group] [--region] [--histogram] [--nosuffix] [--notimesuffix] [--units units] . --allprograms . . -v --verbose . - --region . --area . --histogram . print [device_name] [--clear] [--allprograms|--programid id] [--allregions|--regionid id] . report [device_name] [--interval seconds] [--count count] [--units units] [--allprograms|--programid id] [--allregions| --regionid id] [--area] [--group] [--region] [--histogram] [--nosuffix] [--notimesuffix] [--units units] [-O|--sort sort_fields] [-S|--select selection] . count --interval . . --allprograms . --histogram . --relative / . ( ) --area --region --group . ungroup [device_name|--alldevices] [--groupid id] . --groupid . update_filemap file_path [--follow follow_mode] [--foreground] [--groupid id] [--nomonitor] dmstats group_id --filemap dmfilemapd(8) . . dmfilemapd(8) filemap . --nomonitor (kill) update_filemap . --nomonitor . (REGIONS, AREAS, AND GROUPS) . : . (area) ( ) . . . . . ( ) region_id : . . --start --length . ( : [stripes] RAID). . --areas --areasize create . . (Region identifiers) . ( program_id). region_id . region_id (opaque) . (Group identifiers) . group_id (opaque) . (FILE MAPPING) --filemap . / . ioctl FIEMAP ( ). xfs(5) ext4(5) . basename(3) . . () list report --group . update_filemap dmfilemapd(8) . (File follow modes) : follow-inode follow-path. (unlink) . follow-inode . ( ) unlink . unlink . follow-inode unlink . follow-path . . unlink rename . follow-path ( ) . : . (kill) : ( update_filemap ). create --filemap --follow --nomonitor . (Limitations) / (thread) ( dd(1)). dmstats . : . / . . (REPORT FIELDS) dmstats . (per-area) . (Derived metrics) . iostat . reads_merged_per_sec . writes_merged_per_sec . reads_per_sec . writes_per_sec . read_size_per_sec . write_size_per_sec . avg_request_size . queue_size . await . r_await . w_await . throughput (throughput) . service_time ( ) . util (CPU) / ( ). . (Group, region and area meta fields) . . region_id . . region_start . --units . region_len . --units . area_id . . . . area_start . --units . area_len . --units . area_count . program_id . user_data . group_id . group dmstats . interval_ns . . interval . . (Basic counters) . . /proc/diskstats /sys/block/*/*/stat . . read_count . reads_merged_count . read_sector_count . read_time (). write_count . writes_merged_count . write_sector_count . write_time (). in_progress_count . io_ticks . queue_ticks / / / / / . / (backlog) . read_ticks . write_ticks . (Histogram fields) / . . . hist_count . / . hist_count_bounds : . hist_count_ranges : . hist_percent . / . hist_percent_bounds . / . hist_percent_ranges . / . hist_bounds . . hist_ranges . "LOWER-UPPER" . hist_bins . (EXAMPLES) vg00/lvol1 # dmstats create vg00/lvol1 vg00/lvol1: Created new region with 1 area(s) as region ID 0 d0 # dmstats create --start 1G --length 32M d0 d0: Created new region with 1 area(s) as region ID 0 # 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 # dmstats delete --alldevices --allregions vg00/lvol1 dmsetup # dmsetup stats create --areasize 10G vg00/lvol1 vg00-lvol1: Created new region with 5 area(s) as region ID 1 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 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 vg00/lvol1 # dmstats report --interval 1 --count 5 vg00/lvol1 # dmstats report Name RgID ArID AStart ASize RRqM/s WRqM/s R/s -> vg00-lvol1 0 0 0 61.00g 0.00 0.00 0.00 vg00-lvol1 1 0 61.00g 19.20g 0.00 0.00 0.00 vg00-lvol1 2 0 80.20g 2.14g 0.00 0.00 0.00 -> W/s RSz/s WSz/s AvRqSz QSize Util% AWait RdAWa WrAWa 218.00 0.00 1.04m 4.50k 2.97 81.70 13.62 0.00 13.62 5.00 0.00 548.00k 109.50k 0.14 11.00 27.40 0.00 27.40 14.00 0.00 1.15m 84.00k 0.39 18.70 27.71 0.00 27.71 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 images/ # 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. 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 (SEE ALSO) dmfilemapd(8), dmsetup(8), ext4(5), xfs(5) LVM2: (Device-mapper): : Documentation/device-mapper/statistics.txt Linux Mar 23 2025 DMSTATS(8)