avg_latency document

 I am looking through document about performance, especially on performance data avg_latency, I saw somebody posted this 6 years ago:


To understand more about a specific counter you can get details from the perf-object-counter-list-info API call:


        <desc>Average latency in microseconds for all operations on the volume</desc>
I am looking at


But not seem to find this information.
Where should I look for this? Thanks!