[MC-298464] Memory leak in hoglin farm due to CHANGED

Memory Leak in Hoglin Farm (VisualVM Analysis, Fig. 1)
A memory leak has been identified in a Hoglin farm (Fig. 2) in Minecraft 1.21.5. The farm was built in the crimson_forest biome and relies on despawning Hoglins in the Overworld when no player is within 128 blocks.

The issue also reproduces in earlier versions with a similar farm design (Fig. 3), as reported by Cupperum29 and marcogao.

Root Cause Hypothesis:
This appears to be a special case of entity retention when Hoglins are removed due to CHANGED_DIMENSION, referencing

MC-260605

Attachments

324384fdcbc5958872794f250ca37913_720-20250601-064545.png

Comments 1

hayanesuru 2025-07-15T16:00:33Z

public class CombatTracker {
    private final List<CombatEntry> entries = Lists.newArrayList();
}

public record CombatEntry(DamageSource source, float damage, @Nullable FallLocation fallLocation, float fallDistance) {
}

public class DamageSource {
    private final Holder<DamageType> type;
    private final Entity causingEntity;
    private final Entity directEntity;
    private final Vec3 damageSourcePosition;
}

public abstract class LivingEntity extends Entity implements Attackable, WaypointTransmitter {
    public void remove(Entity.RemovalReason removalReason) {
        if ((removalReason == Entity.RemovalReason.KILLED || removalReason == Entity.RemovalReason.DISCARDED)
            && this.level() instanceof ServerLevel serverLevel) {
            this.triggerOnDeathMobEffects(serverLevel, removalReason);
        }

        super.remove(removalReason);
        this.brain.clearMemories();
        // leak CombatTracker#entries ?
    }
}

Memory leak in hoglin farm due to CHANGED_DIMENSION entity removal

Attachments

Comments 1