[infinispan-dev] Equivalence vs. MurmurHash3

[Radim Vansa]

Hi guys,

I have noticed that even in library mode we use MurmurHash3 to find out 
the segment for particular key. For strings, this involves encoding into 
UTF-8 and computation of hashCode, instead of just reading the cached 
value in string. Common objects just remix the bits of hashCode. When 
user provides custom Equivalence with non-default hashCode, it is not 
used to determine the segment.

I think that in library mode we should rather use Equivalence.hashCode, 
maybe XORed with some magic number so that there are less collisions in 
DataContainer.

If we simply replaced the function in CH, we would break the case when 
user starts HR server on top of library mode, as the clients expect key 
location based on MurmurHash3. ATM user only has to set 
AnyServerEquivalence for keys in DC; we would need to detect 
configuration with server equivalence and set CH function to MH3, and 
probably also log some warning if the equivalence is set to unknown 
class and CH function is not specified.

WDYT?

Radim

-- 
Radim Vansa <rvansa at redhat.com>
JBoss Performance Team