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.
86 lines
2.1 KiB
86 lines
2.1 KiB
.TH cachestat 8 "2016-01-30" "USER COMMANDS"
|
|
.SH NAME
|
|
cachestat \- Statistics for linux page cache hit/miss ratios. Uses Linux eBPF/bcc.
|
|
.SH SYNOPSIS
|
|
.B cachestat
|
|
[-T] [interval [count]]
|
|
.SH DESCRIPTION
|
|
This traces four kernel functions and prints per-second summaries. This can
|
|
be useful for general workload characterization, and looking for patterns
|
|
in operation usage over time.
|
|
|
|
This works by tracing kernel page cache functions using dynamic tracing, and will
|
|
need updating to match any changes to these functions. Edit the script to
|
|
customize which functions are traced.
|
|
|
|
Since this uses BPF, only the root user can use this tool.
|
|
.SH REQUIREMENTS
|
|
CONFIG_BPF and bcc.
|
|
.SH EXAMPLES
|
|
.TP
|
|
Print summaries every five second:
|
|
#
|
|
.B cachestat
|
|
.TP
|
|
Print summaries every five seconds with timestamp:
|
|
#
|
|
.B cachestat -T
|
|
.TP
|
|
Print summaries each second:
|
|
#
|
|
.B cachestat 1
|
|
.TP
|
|
Print output every five seconds, three times:
|
|
#
|
|
.B cachestat 5 3
|
|
.TP
|
|
Print output with timestamp every five seconds, three times:
|
|
#
|
|
.B cachestat -T 5 3
|
|
.SH FIELDS
|
|
.TP
|
|
TIME
|
|
Timestamp.
|
|
.TP
|
|
HITS
|
|
Number of page cache hits.
|
|
.TP
|
|
MISSES
|
|
Number of page cache misses.
|
|
.TP
|
|
DIRTIES
|
|
Number of dirty pages added to the page cache.
|
|
.TP
|
|
READ_HIT%
|
|
Read hit percent of page cache usage.
|
|
.TP
|
|
WRITE_HIT%
|
|
Write hit percent of page cache usage.
|
|
.TP
|
|
BUFFERS_MB
|
|
Buffers size taken from /proc/meminfo.
|
|
.TP
|
|
CACHED_MB
|
|
Cached amount of data in current page cache taken from /proc/meminfo.
|
|
.SH OVERHEAD
|
|
This traces various kernel page cache functions and maintains in-kernel counts, which
|
|
are asynchronously copied to user-space. While the rate of operations can
|
|
be very high (>1G/sec) we can have up to 34% overhead, this is still a relatively efficient way to trace
|
|
these events, and so the overhead is expected to be small for normal workloads.
|
|
Measure in a test environment.
|
|
.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
|
|
Allan McAleavy
|
|
.SH SEE ALSO
|
|
https://github.com/brendangregg/perf-tools/blob/master/fs/cachestat
|