performance/io-cache: change the hash function used for rbtree based hash table.

- the earlier hash function does not distribute pages uniformly for offsets that
    fit into 32 bits. The reason is that the hash function just xors the contents of
    the key 4 bytes at a time with the current value of hash. Hence for keys that
    fit into 32 bits, the hash will be the key itself. Since we are using the
    rounded_offset (which is a multiple of 128KB) as the key, the key will
    be exactly divisible by the number of buckets configured (4096) resolving all
    the pages into the first bucket.

Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 335 (Io-cache optimization)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=335

0 files changed, 0 insertions, 0 deletions