.\"
.\" Copyright (c) 2025 Mateusz Piotrowski <0mp@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 3, 2025
.Dt DTRACE_VFS 4
.Os
.Sh NAME
.Nm dtrace_vfs
.Nd a DTrace provider for Virtual File System
.Sh SYNOPSIS
.Sm off
.Nm vfs Cm : fplookup : Ar function Cm : Ar name
.Nm vfs Cm : namecache : Ar function Cm : Ar name
.Nm vfs Cm : namei : Ar function Cm : Ar name
.Nm vfs Cm : vop : Ar function Cm : Ar name
.Sm on
.Sh DESCRIPTION
The DTrace
.Nm vfs
provider allows users to trace events in the
.Xr VFS 9
layer, the kernel interface for file systems on
.Fx .
.Pp
Run
.Ql dtrace -l -P vfs
to list all
.Nm vfs
probes.
Add
.Fl v
to generate program stability reports,
which contain information about the number of probe arguments and their types.
.Pp
The
.Cm fplookup
module defines a single probe,
.Fn vfs:fplookup:lookup:done "struct nameidata *ndp" "int line" "bool status_code" ,
that instruments the fast path lookup code in
.Xr VFS 9 .
.Pp
The
.Cm namecache
module provides probes related to the
.Xr VFS 9
cache.
Consult the source code in
.Pa src/sys/kern/vfs_cache.c
for more details.
.Pp
The
.Cm namei
module manages probes related to pathname translation and lookup operations.
Refer to
.Xr namei 9
to learn more.
.Pp
The
.Cm vop
module contains probes related to the functions responsible for
.Xr vnode 9
operations.
.Sh COMPATIBILITY
This provider is specific to
.Fx .
.Sh EXAMPLES
Check what lookups failed to be handled in a lockless manner:
.Bd -literal -offset 2n
# dtrace -n 'vfs:fplookup:lookup:done { @[arg1, arg2] = count(); }'
.Ed
.Sh SEE ALSO
.Xr dtrace 1 ,
.Xr d 7 ,
.Xr SDT 9 ,
.Xr namei 9 ,
.Xr VFS 9
.Rs
.%A Brendan Gregg
.%A Jim Mauro
.%B DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD
.%I Prentice Hall
.%P pp. 335\(en351
.%D 2011
.%U https://www.brendangregg.com/dtracebook/
.Re
.Sh AUTHORS
.An -nosplit
The
.Fx
.Nm vfs
provider was written by
.An Robert Watson Aq Mt rwatson@FreeBSD.org .
.Pp
This manual page was written by
.An Mateusz Piotrowski Aq Mt 0mp@FreeBSD.org .