AsmHandler.overrideLightValue causes significant overhead when used alongside Alfheim

[Userrr67]

Mods:

• Quantum Things
• Alfheim (lighting engine replacement)

Description:
AsmHandler.overrideLightValue() hooks into Block.getLightValue() via ASM bytecode injection. Because Alfheim calls getLightValue() on every single block during its light propagation passes, the Random Things ASM hook runs on every one of those calls, adding measurable overhead to every lighting calculation in the game.

Additionally, RTEventHandler.notifyNeighbors() is being triggered as a side effect of lighting updates, which causes further unnecessary work.

Profiler trace:

dev.redstudio.alfheim.lighting.LightUtil.getLightValueForState() 1.43%
  net.minecraft.block.Block.getLightValue() 1.38%
    lumien.randomthings.handler.AsmHandler.overrideLightValue() 1.01%
      lumien.randomthings.handler.AsmHandler.overrideLightValueServer() 0.44%

lumien.randomthings.handler.RTEventHandler.notifyNeighbors() 0.15%
lumien.randomthings.handler.AsmHandler.overrideFallThrough() 0.09%

The overrideLightValue hook alone accounts for ~1% of total server CPU time, purely as overhead on Alfheim's lighting passes.

Expected behavior:
The ASM hook should ideally be a no-op or skip quickly when the block has no Random Things-specific light override, to avoid adding cost to every lighting calculation from other mods.

Possible fix:
An early-exit check in overrideLightValue before doing any meaningful work, e.g. checking if the block is registered with Random Things' light override system before proceeding, would eliminate most of the overhead.

[MagicJinn]

Sorry for perhaps a silly question, but is this in the latest Quantum Things version? I've made some improvements to overrideLightValue in that version, so it might at least lessen the issue.

[Userrr67]

Version 1.2.0

[Userrr67]

After looking at the full profiler data more closely, the overhead isn't just the ASM hook in isolation, a big part of it is worldgen.

WorldGenEventHandler.decorateBiome() → WorldGenPlants → BlockBeanSprout and WorldGenPatches → BlockGlowingMushroom.canBlockStay() are both triggering full Alfheim lighting engine cascades during chunk generation. Every time one of those blocks gets placed in a new chunk, it forces Alfheim to run a complete light recalculation chain.

On top of that, the ASM hook also fires from inside Alfheim's own pipeline, you can see overrideLightValue() appearing again nested under LightUtil.getLightValueForState() near the bottom of the Alfheim chain, so it ends up getting called twice per lighting operation in some cases.

Disabling worldgen spawning of GlowingMushrooms and BeanSprouts would likely cut the cost significantly, since that removes the lighting cascade trigger entirely. The base hook overhead on its own is comparatively small.