What does this sentence mean in the context of perf tool: "Supports address when precise (Precise event)"?

Question

This line appears under memory events in perf tool. CPU: Intel Xeon Gold

Answer 1

"Precise" events mean using PEBS instead of the traditional firing an interrupt when the counter overflows. Instead it writes a sample in a buffer to be collected later, so it can attribute it to the right instruction without pipeline / retirement effects delaying it (e.g. waiting until the currently-last instruction retires, I think to ensure forward progress, causing a "skid").

The PEBS buffer also gives it a place to put additional data, like an address associated with the event that triggered recording a sample.

https://easyperf.net/blog/2018/06/08/Advanced-profiling-topics-PEBS-and-LBR#processor-event-based-sampling-pebs

Also related with discussion about or details of PEBS and how perf uses it for event:pp -

• Good resources on how to program PEBS (Precise event based sampling) counters?
• What is the difference between "cpu/mem-loads/pp" and "cpu/mem-loads/"?
• Which perf events can use PEBS?
• Perf shows L1-dcache-load-misses in a block with no memory access