ZGC has the nice feature that it prints some basic info and configuration with the tag-set [gc, info] at startup. I find this very useful when looking at logs to quickly see what has been run.

Sample output for -Xlog:gc,gc+init:
[0.006s][info][gc] Using G1
[0.012s][info][gc,init] Version: 15-internal+0-2020-05-11-1350562.sjohanss... (release)
[0.012s][info][gc,init] CPUs: 24 total, 24 available
[0.012s][info][gc,init] Memory: 32109M
[0.012s][info][gc,init] Large Page Support: Disabled
[0.012s][info][gc,init] NUMA Support: Enabled
[0.013s][info][gc,init] NUMA Nodes: 2
[0.013s][info][gc,init] Compressed Oops: Enabled (Zero based)
[0.013s][info][gc,init] Heap Region Size: 4M
[0.013s][info][gc,init] Heap Min Capacity: 8M
[0.013s][info][gc,init] Heap Initial Capacity: 504M
[0.013s][info][gc,init] Heap Max Capacity: 8028M
[0.013s][info][gc,init] Pre-touch: Disabled
[0.013s][info][gc,init] Parallel Workers: 18
[0.013s][info][gc,init] Concurrent Workers: 5
[0.013s][info][gc,init] Concurrent Refinement Workers: 18
[0,029s][info][gc ] Periodic GC disabled