---
name: "dcstat-bpfcc"
section: "8"
platform: "linux"
package: "bpfcc-tools"
version: "0.31.0+ds-7"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/dcstat-bpfcc"
---

# dcstat-bpfcc(8)

Directory entry cache (dcache) stats. Uses Linux eBPF/bcc.

## NAME

dcstat - Directory entry cache (dcache) stats. Uses Linux eBPF/bcc.

## SYNOPSIS

**dcstat** \[interval \[count\]\]

## DESCRIPTION

The Linux directory entry cache (dcache) improves the performance of file and directory name lookups. This tool provides per-second summary statistics of dcache performance.

This uses kernel dynamic tracing of kernel functions, lookup\_fast() and d\_lookup(), which will need to be modified to match kernel changes.

Since this uses BPF, only the root user can use this tool.

## REQUIREMENTS

CONFIG\_BPF and bcc.

## EXAMPLES

- Print summaries each second:

  \# **dcstat**

- Print output every five seconds, three times:

  \# **dcstat 5 3**

## FIELDS

- REFS/s

  Number dcache lookups (references) per second.

- SLOW/s

  Number of dcache lookups that failed the lookup\_fast() path and executed the lookup\_slow() path instead.

- MISS/s

  Number of dcache misses (failed both fast and slow lookups).

- HIT%

  Percentage of dcache hits over total references.

## OVERHEAD

The overhead depends on the frequency of file and directory name lookups. While the per-event overhead is low, some applications may make over 100k lookups per second, and the low per-event overhead will begin to add up, and could begin to be measurable (over 10% CPU usage). Measure in a test environment.

## SOURCE

This is from bcc.

-

  https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion \_examples.txt file containing example usage, output, and commentary for this tool.

## OS

Linux

## STABILITY

Unstable - in development.

## AUTHOR

Brendan Gregg

## SEE ALSO

dcsnoop(8)