[jira] [Created] (HBASE-24915) Improve BlockCache read performance by specifying BlockType

["fanrui (Jira)" <ji...@apache.org>]

fanrui created HBASE-24915:
------------------------------

             Summary: Improve BlockCache read performance by specifying BlockType
                 Key: HBASE-24915
                 URL: https://issues.apache.org/jira/browse/HBASE-24915
             Project: HBase
          Issue Type: Improvement
          Components: BlockCache, Performance
            Reporter: fanrui


CombinedBlockCache contains l1Cache and l2Cache. l1Cache stores MetaBlock and l2Cache stores DataBlock. Because getBlock does not know the BlockType, the getBlock of CombinedBlockCache queries l1Cache first, and then l2Cache. But actually querying DataBlock is not necessary to query l1Cache. 

Therefore, in some cases where BlockType is known, BlockCache read performance can be improved.
h2.  Code：

 BlockCache: default call old getBlock
{code:java}
default Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat,
    boolean updateCacheMetrics, BlockType blockType) {
  return getBlock(cacheKey, caching, repeat, updateCacheMetrics);
}
{code}
CombinedBlockCache:
{code:java}
@Override
public Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat,
    boolean updateCacheMetrics, BlockType blockType) {
  if (blockType == null) {
    return getBlock(cacheKey, caching, repeat, updateCacheMetrics);
  }
  boolean metaBlock = isMetaBlock(blockType);
  if (metaBlock) {
    return l1Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics);
  } else {
    return l2Cache.getBlock(cacheKey, caching, repeat, updateCacheMetrics);
  }
}private boolean isMetaBlock(BlockType blockType) {
  return blockType.getCategory() != BlockCategory.DATA;
}
{code}
HFileReaderImpl#getCachedBlock call BlockCache#getBlock(XXX, expectedBlockType)



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