Hi, I'm not an expert at debugging specific memory issues but I only, on the surface, know how to well.. execute the heapdump command and put it into a tool like Eclipse Memory Analyzer.
I recently came across a memory leak issue when upgrading from 1.21.5 -> 1.21.8. Initially, I had no issues with memory but I did do a clean install of Windows right before upgrading to 1.21.8. I did not test if this issue is present on 1.21.5 with a clean install.
I ran
/sparkc heapdump
/sparkc heapdump
and imported it into Eclipse Memory Analyzer. Eclipse told me the suspect was DH. See attached screenshot.
I disabled the mod (by removing it, disabling rendering did nothing) and now Minecraft runs smoothly without any memory leak. Could other mods be interfering with DH or is this a DH issue?