[HBASE-22531] The HFileReaderImpl#shouldUseHeap return the incorrect true when disabled BlockCache

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.3.0
• Hadoop Flags: Reviewed
• Assignee: Zheng Hu
• Reporter: Zheng Hu
• Created: 03/Jun/19 07:58
• Updated: 01/Jul/22 21:46
• Resolved: 14/Jun/19 01:42

Description

I'm having a benchmark with block cache disabled for HBASE-21879 branch. Just caurious about why still so many heap allocation in the heap allocation flame graph async-prof-pid-13311-alloc-4.svg , actually, I've set the following config, which means all allocation should be offheap, while it's not:

# Disable the block cache
hfile.block.cache.size=0
hbase.ipc.server.reservoir.minimal.allocating.size=0   # Let all allocation from pooled allocator. 

Checked the code, I found the problem here:

  private boolean shouldUseHeap(BlockType expectedBlockType) {
    if (cacheConf.getBlockCache() == null) {
      return false;
    } else if (!cacheConf.isCombinedBlockCache()) {
      // Block to cache in LruBlockCache must be an heap one. So just allocate block memory from
      // heap for saving an extra off-heap to heap copying.
      return true;
    }
    return expectedBlockType != null && !expectedBlockType.isData();
  }

Say, the CacheConfig#getBlockCache will return a Optional<BlockCache>, which is always non-null:

  /**
   * Returns the block cache.
   *
   * @return the block cache, or null if caching is completely disabled
   */
  public Optional<BlockCache> getBlockCache() {
    return Optional.ofNullable(this.blockCache);
  }

Issue Links

• links to: GitHub Pull Request #304