llcstat(8) System Manager's Manual llcstat(8)
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 mean-
ings on different architecture. For x86-64, they mean misses and refer-
ences to LLC. This can be useful to locate and debug performance is-
sues 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
USER COMMANDS 2015-08-18 llcstat(8)
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