- bullseye 0.18.0+ds-2
- bullseye-backports 0.22.0+ds-2~bpo11+1
- testing 0.25.0+ds-2
- unstable 0.26.0+ds-1
- experimental 0.26.0+ds-2~experimental1
|dcstat(8)||System Manager's Manual||dcstat(8)|
dcstat - Directory entry cache (dcache) stats. Uses Linux eBPF/bcc.
dcstat [interval [count]]
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.
CONFIG_BPF and bcc.
- Print summaries each second:
- # dcstat
- Print output every five seconds, three times:
- # dcstat 5 3
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.
This is from bcc.
Also look in the bcc distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.
Unstable - in development.