Lars Hofhansl created HBASE-9553:
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             Summary: Pad HFile blocks to a fixed size before placing them into 
the blockcache
                 Key: HBASE-9553
                 URL: https://issues.apache.org/jira/browse/HBASE-9553
             Project: HBase
          Issue Type: Bug
            Reporter: Lars Hofhansl


In order to make it easy on the garbage collector and to avoid full compaction 
phases we should make sure that all (or at least a large percentage) of the 
HFile blocks as cached in the block cache are exactly the same size.

Currently an HFile block is typically slightly larger than the declared block 
size, as the block will accommodate that last KV on the block. The padding 
would be a ColumnFamily option. In many cases 100 bytes would probably be a 
good value to make all blocks exactly the same size (but of course it depends 
on the max size of the KVs).

This does not have to be perfect. The more blocks evicted and replaced in the 
block cache are of the exact same size the easier it should be on the GC.

Thoughts?


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