|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.
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.