[Xen-ia64-devel] rid virtualization

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Dan:
        During early this year, I remembered we ever talked about VHPT
locality issues. The conclusion is that if the rid is randomly allocated
the VHPT entry will be fairly evenly distributed. After that I noticed
that you added vmMangleRID() to try to make the rid as random as
possible. The VTI code has similar code too at that time to switch rid
bits.

        I also did a measurement at that time (in VTI environment
excluding metaphysical map entries) and find a disappoint result that
almost 70-80% of VHPT entries are invalid while the left 20-30% hot
entries has long collision chains (Some even has 30+ entries in chain
vs. average 1). That reminds me to think of RID virtualization to solve
this problem thoroughly and now I am planning to do that covering both
global VHPT and per VP VHPT although it is still in design phase.
        What is your suggestion on that? Or is there anybody else
already thought of this?
Eddie

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