You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
75 lines
1.8 KiB
75 lines
1.8 KiB
.TH llcstat 8 "2015-08-18" "USER COMMANDS"
|
|
.SH NAME
|
|
llcstat \- Summarize CPU cache references and misses by process. Uses Linux eBPF/bcc.
|
|
.SH SYNOPSIS
|
|
.B llcstat [\-h] [\-c SAMPLE_PERIOD] [duration]
|
|
.SH 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.
|
|
.SH REQUIREMENTS
|
|
CONFIG_BPF and bcc.
|
|
.SH OPTIONS
|
|
.TP
|
|
\-h
|
|
Print usage message.
|
|
.TP
|
|
\-c SAMPLE_PERIOD
|
|
Sample one in this many cache reference and cache miss events.
|
|
.TP
|
|
duration
|
|
Duration to trace, in seconds.
|
|
.SH EXAMPLES
|
|
.TP
|
|
Sample one in 100 events, trace for 20 seconds:
|
|
#
|
|
.B llcstat -c 100 20
|
|
.SH FIELDS
|
|
.TP
|
|
PID
|
|
Process ID
|
|
.TP
|
|
NAME
|
|
Process name
|
|
.TP
|
|
CPU
|
|
CPU ID
|
|
.TP
|
|
REFERENCE
|
|
Number of cache reference events
|
|
.TP
|
|
MISS
|
|
Number of cache miss events
|
|
.TP
|
|
HIT%
|
|
Cache hit ratio
|
|
.SH SOURCE
|
|
This is from bcc.
|
|
.IP
|
|
https://github.com/iovisor/bcc
|
|
.PP
|
|
Also look in the bcc distribution for a companion _examples.txt file containing
|
|
example usage, output, and commentary for this tool.
|
|
.SH OS
|
|
Linux
|
|
.SH STABILITY
|
|
Unstable - in development.
|
|
.SH AUTHOR
|
|
Teng Qin
|
|
.SH SEE ALSO
|
|
.TP
|
|
Perf can be used as a generic event counter tool. An example for LLC:
|
|
#
|
|
.B perf top -e cache-misses -e cache-references -a -ns pid,cpu,comm
|