Immutable and cache coherence

[Tomek Sowiński]

I've been reading about caching mechanisms in today's processors -- amazing in their 
intricacy.
It made me wonder, is there a way to exclude immutable regions of memory from a cache 
coherence mechanism? I mean, let the processor know: no invalidation for cache lines from 
immutable memory.
And even if it's possible, how much would it really help? I have no intuition about how 
expensive those coherence mechanisms are.

CPU geeks speak up! :)

-- 
Tomek