---
name: "dtrace_vfs"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/dtrace_vfs"
---

# dtrace\_vfs(4)

a DTrace provider for Virtual File System

## NAME

**dtrace\_vfs** – a DTrace provider for Virtual File System

## SYNOPSIS

**vfs**:**fplookup**:*function*:*name*

**vfs**:**namecache**:*function*:*name*

**vfs**:**namei**:*function*:*name*

**vfs**:**vop**:*function*:*name*

## DESCRIPTION

The DTrace **vfs** provider allows users to trace events in the [VFS(9)](/VFS/9.md) layer, the kernel interface for file systems on FreeBSD.

Run ‘dtrace -l -P vfs’ to list all **vfs** probes. Add **-v** to generate program stability reports, which contain information about the number of probe arguments and their types.

The **fplookup** module defines a single probe, **vfs:fplookup:lookup:done**(*struct nameidata \*ndp*, *int line*, *bool status\_code*), that instruments the fast path lookup code in [VFS(9)](/VFS/9.md).

The **namecache** module provides probes related to the [VFS(9)](/VFS/9.md) cache. Consult the source code in *src/sys/kern/vfs\_cache.c* for more details.

The **namei** module manages probes related to pathname translation and lookup operations. Refer to [namei(9)](/namei/9.md) to learn more.

The **vop** module contains probes related to the functions responsible for [vnode(9)](/vnode/9.md) operations.

## COMPATIBILITY

This provider is specific to FreeBSD.

## EXAMPLES

Check what lookups failed to be handled in a lockless manner:

```
# dtrace -n 'vfs:fplookup:lookup:done { @[arg1, arg2] = count(); }'
```

## SEE ALSO

[dtrace(1)](/dtrace/1.md), [d(7)](/d/7.md), [namei(9)](/namei/9.md), [SDT(9)](/SDT/9.md), [VFS(9)](/VFS/9.md) Brendan Gregg and Jim Mauro, *DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD*, Prentice Hall, pp. 335–351, 2011, https://www.brendangregg.com/dtracebook/.

## AUTHORS

The FreeBSD **vfs** provider was written by Robert Watson ⟨*rwatson@FreeBSD.org*⟩.

This manual page was written by Mateusz Piotrowski ⟨*0mp@FreeBSD.org*⟩.