dcstat-bpfcc8
Directory entry cache (dcache) stats. uses linux ebpf/bcc.
Usage
dcstat [interval
[count]]
Overview
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:
|
# |
|---|---|
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.
Releases
Unchanged in 4 releases since Debian 10 (Buster).