openinx commented on a change in pull request #242: HBASE-22422 Retain an
ByteBuff with refCnt=0 when getBlock from LRUCache
URL: https://github.com/apache/hbase/pull/242#discussion_r284963888
##########
File path:
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/LruBlockCache.java
##########
@@ -611,6 +609,10 @@ protected long evictBlock(LruCachedBlock block, boolean
evictedByEvictionProcess
victimHandler.cacheBlock(block.getCacheKey(), block.getBuffer());
}
}
+ // Decrease the block's reference count, and if refCount is 0, then it'll
auto-deallocate. DO
+ // NOT move this up because if do that then the victimHandler may access
the buffer with
+ // refCnt = 0 which is disallowed.
+ previous.getBuffer().release();
Review comment:
> Why in victimHandler we will access the previous? And is it possible to
add a UT?
For InclusiveCombinedBlockCache , we will move the evicted block from
LRUCache to an larger L2 cache (such as MemcachedBlockCache for longer caching
I think), So if release in line#596, then victimHandler will cache an block
which point to an unknown area because its memory has been free.
Yeah, will provide a UT.
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