dbufstat.1

DBUFSTAT(1)

General Commands Manual

DBUFSTAT(1)

NAME

dbufstat — display statistics for DMU buffer cache

SYNOPSIS

dbufstat [-bdhnrtvx] [-f field[,field…]] [-F field=value[,…]] [-i file] [-o file] [-s separator]

DESCRIPTION

dbufstat displays statistics about the DMU (Data Management Unit) buffer cache, also known as the dbuf cache. This information is read from the dbufs kstat (/proc/spl/kstat/zfs/dbufs on Linux and kstat.zfs.misc.dbufs on FreeBSD).

dbufstat can display data in three modes:

-b: Display a table of information for each individual dbuf (buffer). This is the most detailed view.
-d: Display a table of information for each dnode (the default mode). Multiple dbufs belonging to the same dnode are aggregated.
-t: Display a table of information for each dnode type. Multiple dnodes of the same type are aggregated.

The following fields are available for display. Not all fields are compatible with all modes; use -v to see which fields are incompatible with each mode.

pool: Pool name.
objset: Dataset identification number.
object: Object number.
level: Indirection level of buffer.
blkid: Block number of buffer.
offset: Offset in object of buffer.
dbsize: Size of buffer.
usize: Size of attached user data.
meta: Whether this buffer is metadata.
state: State of buffer (read, cached, etc).
dbholds: Number of holds on buffer.
dbc: Whether this buffer is in the dbuf cache.
list: Which ARC list contains this buffer.
atype: ARC header type (data or metadata).
flags: ARC read flags.
count: ARC data count.
asize: Size of this ARC buffer.
access: Time this ARC buffer was last accessed.
mru: Hits while on the ARC's MRU list.
gmru: Hits while on the ARC's MRU ghost list.
mfu: Hits while on the ARC's MFU list.
gmfu: Hits while on the ARC's MFU ghost list.
l2: Hits while on the L2ARC.
l2_dattr: L2ARC disk address/offset.
l2_asize: L2ARC allocated size (depends on compression).
l2_comp: L2ARC compression algorithm for buffer.
aholds: Number of holds on this ARC buffer.
dtype: Dnode type.
btype: Bonus buffer type.
data_bs: Data block size.
meta_bs: Metadata block size.
bsize: Bonus buffer size.
lvls: Number of indirection levels.
dholds: Number of holds on dnode.
blocks: Number of allocated blocks.
dsize: Size of dnode.
cached: Bytes cached for all blocks.
direct: Bytes cached for direct blocks.
indirect: Bytes cached for indirect blocks.
bonus: Bytes cached for bonus buffer.
spill: Bytes cached for spill block.

OPTIONS

-b: Display information for each individual dbuf.
-d: Display information for each dnode (default).
-f field[,field…]: Display only the specified fields.
-F field=value[,…]: Filter output by field value or regular expression. Multiple filters may be specified as a comma-separated list.
-h: Display a help message.
-i file: Redirect input from the specified file instead of the dbufs kstat.
-n: Exclude the header from output.
-o file: Redirect output to the specified file instead of standard output.
-r: Display raw values. Specify twice to also display numeric type and compression identifiers instead of names.
-s separator: Override the default field separator (two spaces) with a custom character or string.
-t: Display information for each dnode type.
-v: List all possible field headers, definitions, and incompatibilities for each mode.
-x: Display extended statistics.

EXAMPLES

Display per-dnode statistics (default mode):

# 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

Display per-type statistics:

# 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

Display per-buffer statistics:

# 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

Display specific fields per dnode:

# dbufstat
  -d -f
  pool,object,objset,dsize,cached

Display per-type statistics with comma-separated output:

# dbufstat
  -t -s
  ""

,

Display extended per-buffer statistics with filters:

# dbufstat
  -bx -F
  dbc=1,pool=zroot

AUTHORS

This man page was written by Christos Longros <chris.longros@gmail.com>.

March 19, 2026

Debian