---
name: "llcstat-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/llcstat-bpfcc"
---

# llcstat-bpfcc(8)

Summarize CPU cache references and misses by process. Uses Linux eBPF/bcc.

## NAME

llcstat - Summarize CPU cache references and misses by process. Uses Linux eBPF/bcc.

## SYNOPSIS

**llcstat \[-h\] \[-c SAMPLE\_PERIOD\] \[duration\]**

## DESCRIPTION

llcstat instruments CPU cache references and cache misses system-side, and summarizes them by PID and CPU. These events have different meanings on different architecture. For x86-64, they mean misses and references to LLC. This can be useful to locate and debug performance issues caused by cache hit rate.

This works by sampling corresponding events defined in uapi/linux/perf\_event.h, namely PERF\_COUNT\_HW\_CACHE\_REFERENCES and PERF\_COUNT\_HW\_CACHE\_MISSES, using BPF perf event tracing. Upon each sampled event, the attached BPF program records the PID and CPU ID on which the event happened, and stores it in table.

This makes use of a Linux 4.9 feature (BPF\_PROG\_TYPE\_PERF\_EVENT).

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

## REQUIREMENTS

CONFIG\_BPF and bcc.

## OPTIONS

- \-h

  Print usage message.

- \-c SAMPLE\_PERIOD

  Sample one in this many cache reference and cache miss events.

- \-t

  Summarize cache references and misses by PID/TID

- duration

  Duration to trace, in seconds.

## EXAMPLES

- Sample one in 100 events, trace for 20 seconds:

  \# **llcstat -c 100 20**

## FIELDS

- PID

  Process ID

- NAME

  Process name

- CPU

  CPU ID

- REFERENCE

  Number of cache reference events

- MISS

  Number of cache miss events

- HIT%

  Cache hit ratio

## 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

Teng Qin

## SEE ALSO

- Perf can be used as a generic event counter tool. An example for LLC:

  \# **perf top -e cache-misses -e cache-references -a -ns pid,cpu,comm**