rac cache fusion tuning

I am running 10g2 on 4 hp bp20 blades, with rhe3.

I am getting many of the following:

Metrics "Global Cache Average Current Get Time" is at 1.46667 
Metrics "Global Cache Blocks Lost" is at 4 
Metrics "Global Cache Average CR Get Time" is at 2.16129

I have already set rmem_default, rmem_max, wmem_default, wmem_max all to 262144.

What else can be done?

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