1.\" SPDX-License-Identifier: CDDL-1.0 2.\" 3.\" This file and its contents are supplied under the terms of the 4.\" Common Development and Distribution License ("CDDL"), version 1.0. 5.\" You may only use this file in accordance with the terms of version 6.\" 1.0 of the CDDL. 7.\" 8.\" A full copy of the text of the CDDL should have accompanied this 9.\" source. A copy of the CDDL is also available via the Internet at 10.\" http://www.illumos.org/license/CDDL. 11.\" 12.\" Copyright (C) 2013 Lawrence Livermore National Security, LLC. 13.\" 14.Dd March 19, 2026 15.Dt DBUFSTAT 1 16.Os 17. 18.Sh NAME 19.Nm dbufstat 20.Nd display statistics for DMU buffer cache 21.Sh SYNOPSIS 22.Nm 23.Op Fl bdhnrtvx 24.Op Fl f Ar field Ns Op , Ns Ar field Ns … 25.Op Fl F Ar field Ns = Ns Ar value Ns Op , Ns … 26.Op Fl i Ar file 27.Op Fl o Ar file 28.Op Fl s Ar separator 29. 30.Sh DESCRIPTION 31.Nm 32displays statistics about the DMU (Data Management Unit) buffer 33cache, also known as the dbuf cache. 34This information is read from the 35.Sy dbufs 36kstat 37.Po Pa /proc/spl/kstat/zfs/dbufs 38on Linux and 39.Sy kstat.zfs.misc.dbufs 40on FreeBSD 41.Pc . 42.Pp 43.Nm 44can display data in three modes: 45.Bl -tag -width "-b" 46.It Fl b 47Display a table of information for each individual dbuf 48(buffer). 49This is the most detailed view. 50.It Fl d 51Display a table of information for each dnode 52(the default mode). 53Multiple dbufs belonging to the same dnode are 54aggregated. 55.It Fl t 56Display a table of information for each dnode type. 57Multiple dnodes of the same type are aggregated. 58.El 59.Pp 60The following fields are available for display. 61Not all fields are compatible with all modes; use 62.Fl v 63to see which fields are incompatible with each mode. 64.Bl -tag -compact -offset Ds -width "indirect" 65.It Sy pool 66Pool name. 67.It Sy objset 68Dataset identification number. 69.It Sy object 70Object number. 71.It Sy level 72Indirection level of buffer. 73.It Sy blkid 74Block number of buffer. 75.It Sy offset 76Offset in object of buffer. 77.It Sy dbsize 78Size of buffer. 79.It Sy usize 80Size of attached user data. 81.It Sy meta 82Whether this buffer is metadata. 83.It Sy state 84State of buffer (read, cached, etc). 85.It Sy dbholds 86Number of holds on buffer. 87.It Sy dbc 88Whether this buffer is in the dbuf cache. 89.It Sy list 90Which ARC list contains this buffer. 91.It Sy atype 92ARC header type (data or metadata). 93.It Sy flags 94ARC read flags. 95.It Sy count 96ARC data count. 97.It Sy asize 98Size of this ARC buffer. 99.It Sy access 100Time this ARC buffer was last accessed. 101.It Sy mru 102Hits while on the ARC's MRU list. 103.It Sy gmru 104Hits while on the ARC's MRU ghost list. 105.It Sy mfu 106Hits while on the ARC's MFU list. 107.It Sy gmfu 108Hits while on the ARC's MFU ghost list. 109.It Sy l2 110Hits while on the L2ARC. 111.It Sy l2_dattr 112L2ARC disk address/offset. 113.It Sy l2_asize 114L2ARC allocated size (depends on compression). 115.It Sy l2_comp 116L2ARC compression algorithm for buffer. 117.It Sy aholds 118Number of holds on this ARC buffer. 119.It Sy dtype 120Dnode type. 121.It Sy btype 122Bonus buffer type. 123.It Sy data_bs 124Data block size. 125.It Sy meta_bs 126Metadata block size. 127.It Sy bsize 128Bonus buffer size. 129.It Sy lvls 130Number of indirection levels. 131.It Sy dholds 132Number of holds on dnode. 133.It Sy blocks 134Number of allocated blocks. 135.It Sy dsize 136Size of dnode. 137.It Sy cached 138Bytes cached for all blocks. 139.It Sy direct 140Bytes cached for direct blocks. 141.It Sy indirect 142Bytes cached for indirect blocks. 143.It Sy bonus 144Bytes cached for bonus buffer. 145.It Sy spill 146Bytes cached for spill block. 147.El 148. 149.Sh OPTIONS 150.Bl -tag -width "-F filter" 151.It Fl b 152Display information for each individual dbuf. 153.It Fl d 154Display information for each dnode (default). 155.It Fl f Ar field Ns Op , Ns Ar field Ns … 156Display only the specified fields. 157.It Fl F Ar field Ns = Ns Ar value Ns Op , Ns … 158Filter output by field value or regular expression. 159Multiple filters may be specified as a comma-separated list. 160.It Fl h 161Display a help message. 162.It Fl i Ar file 163Redirect input from the specified file instead of the 164.Sy dbufs 165kstat. 166.It Fl n 167Exclude the header from output. 168.It Fl o Ar file 169Redirect output to the specified file instead of standard output. 170.It Fl r 171Display raw values. 172Specify twice to also display numeric type and compression 173identifiers instead of names. 174.It Fl s Ar separator 175Override the default field separator (two spaces) with a 176custom character or string. 177.It Fl t 178Display information for each dnode type. 179.It Fl v 180List all possible field headers, definitions, and 181incompatibilities for each mode. 182.It Fl x 183Display extended statistics. 184.El 185. 186.Sh EXAMPLES 187Display per-dnode statistics (default mode): 188.Bd -literal -compact -offset Ds 189# dbufstat -d 190 pool objset object dtype cached 191 zroot 30 34466 DMU_OT_DIRECTORY_CONTENTS 240K 192 zroot 30 0 DMU_OT_DNODE 14M 193 zroot 30 36343 DMU_OT_DIRECTORY_CONTENTS 1024 194 zroot 30 32921 DMU_OT_PLAIN_FILE_CONTENTS 2.5K 195.Ed 196.Pp 197Display per-type statistics: 198.Bd -literal -compact -offset Ds 199# dbufstat -t 200 pool objset dtype cached 201 zroot 30 DMU_OT_DIRECTORY_CONTENTS 1.9M 202 zroot 30 DMU_OT_DNODE 14M 203 zroot 30 DMU_OT_PLAIN_FILE_CONTENTS 8.4M 204 zroot 0 DMU_OT_DSL_PROPS 2.6M 205.Ed 206.Pp 207Display per-buffer statistics: 208.Bd -literal -compact -offset Ds 209# dbufstat -b 210 pool objset object level blkid offset dbsize 211 zroot 30 34466 1 0 0 128K 212 zroot 30 0 0 292 4.6M 16K 213 zroot 30 34466 0 8 128K 16K 214 zroot 0 4 0 0 0 128K 215.Ed 216.Pp 217Display specific fields per dnode: 218.Dl # Nm dbufstat Fl d Fl f Ar pool,object,objset,dsize,cached 219.Pp 220Display per-type statistics with comma-separated output: 221.Dl # Nm dbufstat Fl t Fl s Qq , 222.Pp 223Display extended per-buffer statistics with filters: 224.Dl # Nm dbufstat Fl bx Fl F Ar dbc=1,pool=zroot 225. 226.Sh SEE ALSO 227.Xr zarcstat 1 , 228.Xr zfs 8 , 229.Xr zpool-iostat 8 230. 231.Sh AUTHORS 232This man page was written by 233.An Christos Longros Aq Mt chris.longros@gmail.com . 234