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.\" SPDX-License-Identifier: CDDL-1.0
.\"
.\" This file and its contents are supplied under the terms of the
.\" Common Development and Distribution License ("CDDL"), version 1.0.
.\" You may only use this file in accordance with the terms of version
.\" 1.0 of the CDDL.
.\"
.\" A full copy of the text of the CDDL should have accompanied this
.\" source. A copy of the CDDL is also available via the Internet at
.\" http://www.illumos.org/license/CDDL.
.\"
.\" Copyright (C) 2013 Lawrence Livermore National Security, LLC.
.\"
.Dd March 19, 2026
.Dt DBUFSTAT 1
.Os
.
.Sh NAME
.Nm dbufstat
.Nd display statistics for DMU buffer cache
.Sh SYNOPSIS
.Nm
.Op Fl bdhnrtvx
.Op Fl f Ar field Ns Op , Ns Ar field Ns …
.Op Fl F Ar field Ns = Ns Ar value Ns Op , Ns …
.Op Fl i Ar file
.Op Fl o Ar file
.Op Fl s Ar separator
.
.Sh DESCRIPTION
.Nm
displays statistics about the DMU (Data Management Unit) buffer
cache, also known as the dbuf cache.
This information is read from the
.Sy dbufs
kstat
.Po Pa /proc/spl/kstat/zfs/dbufs
on Linux and
.Sy kstat.zfs.misc.dbufs
on FreeBSD
.Pc .
.Pp
.Nm
can display data in three modes:
.Bl -tag -width "-b"
.It Fl b
Display a table of information for each individual dbuf
(buffer).
This is the most detailed view.
.It Fl d
Display a table of information for each dnode
(the default mode).
Multiple dbufs belonging to the same dnode are
aggregated.
.It Fl t
Display a table of information for each dnode type.
Multiple dnodes of the same type are aggregated.
.El
.Pp
The following fields are available for display.
Not all fields are compatible with all modes; use
.Fl v
to see which fields are incompatible with each mode.
.Bl -tag -compact -offset Ds -width "indirect"
.It Sy pool
Pool name.
.It Sy objset
Dataset identification number.
.It Sy object
Object number.
.It Sy level
Indirection level of buffer.
.It Sy blkid
Block number of buffer.
.It Sy offset
Offset in object of buffer.
.It Sy dbsize
Size of buffer.
.It Sy usize
Size of attached user data.
.It Sy meta
Whether this buffer is metadata.
.It Sy state
State of buffer (read, cached, etc).
.It Sy dbholds
Number of holds on buffer.
.It Sy dbc
Whether this buffer is in the dbuf cache.
.It Sy list
Which ARC list contains this buffer.
.It Sy atype
ARC header type (data or metadata).
.It Sy flags
ARC read flags.
.It Sy count
ARC data count.
.It Sy asize
Size of this ARC buffer.
.It Sy access
Time this ARC buffer was last accessed.
.It Sy mru
Hits while on the ARC's MRU list.
.It Sy gmru
Hits while on the ARC's MRU ghost list.
.It Sy mfu
Hits while on the ARC's MFU list.
.It Sy gmfu
Hits while on the ARC's MFU ghost list.
.It Sy l2
Hits while on the L2ARC.
.It Sy l2_dattr
L2ARC disk address/offset.
.It Sy l2_asize
L2ARC allocated size (depends on compression).
.It Sy l2_comp
L2ARC compression algorithm for buffer.
.It Sy aholds
Number of holds on this ARC buffer.
.It Sy dtype
Dnode type.
.It Sy btype
Bonus buffer type.
.It Sy data_bs
Data block size.
.It Sy meta_bs
Metadata block size.
.It Sy bsize
Bonus buffer size.
.It Sy lvls
Number of indirection levels.
.It Sy dholds
Number of holds on dnode.
.It Sy blocks
Number of allocated blocks.
.It Sy dsize
Size of dnode.
.It Sy cached
Bytes cached for all blocks.
.It Sy direct
Bytes cached for direct blocks.
.It Sy indirect
Bytes cached for indirect blocks.
.It Sy bonus
Bytes cached for bonus buffer.
.It Sy spill
Bytes cached for spill block.
.El
.
.Sh OPTIONS
.Bl -tag -width "-F filter"
.It Fl b
Display information for each individual dbuf.
.It Fl d
Display information for each dnode (default).
.It Fl f Ar field Ns Op , Ns Ar field Ns …
Display only the specified fields.
.It Fl F Ar field Ns = Ns Ar value Ns Op , Ns …
Filter output by field value or regular expression.
Multiple filters may be specified as a comma-separated list.
.It Fl h
Display a help message.
.It Fl i Ar file
Redirect input from the specified file instead of the
.Sy dbufs
kstat.
.It Fl n
Exclude the header from output.
.It Fl o Ar file
Redirect output to the specified file instead of standard output.
.It Fl r
Display raw values.
Specify twice to also display numeric type and compression
identifiers instead of names.
.It Fl s Ar separator
Override the default field separator (two spaces) with a
custom character or string.
.It Fl t
Display information for each dnode type.
.It Fl v
List all possible field headers, definitions, and
incompatibilities for each mode.
.It Fl x
Display extended statistics.
.El
.
.Sh EXAMPLES
Display per-dnode statistics (default mode):
.Bd -literal -compact -offset Ds
# dbufstat -d
pool objset object dtype cached
zroot 30 34466 DMU_OT_DIRECTORY_CONTENTS 240K
zroot 30 0 DMU_OT_DNODE 14M
zroot 30 36343 DMU_OT_DIRECTORY_CONTENTS 1024
zroot 30 32921 DMU_OT_PLAIN_FILE_CONTENTS 2.5K
.Ed
.Pp
Display per-type statistics:
.Bd -literal -compact -offset Ds
# dbufstat -t
pool objset dtype cached
zroot 30 DMU_OT_DIRECTORY_CONTENTS 1.9M
zroot 30 DMU_OT_DNODE 14M
zroot 30 DMU_OT_PLAIN_FILE_CONTENTS 8.4M
zroot 0 DMU_OT_DSL_PROPS 2.6M
.Ed
.Pp
Display per-buffer statistics:
.Bd -literal -compact -offset Ds
# dbufstat -b
pool objset object level blkid offset dbsize
zroot 30 34466 1 0 0 128K
zroot 30 0 0 292 4.6M 16K
zroot 30 34466 0 8 128K 16K
zroot 0 4 0 0 0 128K
.Ed
.Pp
Display specific fields per dnode:
.Dl # Nm dbufstat Fl d Fl f Ar pool,object,objset,dsize,cached
.Pp
Display per-type statistics with comma-separated output:
.Dl # Nm dbufstat Fl t Fl s Qq ,
.Pp
Display extended per-buffer statistics with filters:
.Dl # Nm dbufstat Fl bx Fl F Ar dbc=1,pool=zroot
.
.Sh SEE ALSO
.Xr zarcstat 1 ,
.Xr zfs 8 ,
.Xr zpool-iostat 8
.
.Sh AUTHORS
This man page was written by
.An Christos Longros Aq Mt chris.longros@gmail.com .
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