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https://issues.apache.org/jira/browse/HBASE-23277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16973719#comment-16973719
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Andrew Kyle Purtell commented on HBASE-23277:
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I don't recall a reason for proactive eviction.
I can speculate. My guess is the thought was proactive eviction at close would
be a benefit because it is a signal we no longer care about any of the blocks
in that file, and by clearing them out right away we make immediate room in the
cache for more blocks from files that are still open.
> CompactedHFilesDischarger may lead to high cpu usage
> -----------------------------------------------------
>
> Key: HBASE-23277
> URL: https://issues.apache.org/jira/browse/HBASE-23277
> Project: HBase
> Issue Type: Brainstorming
> Reporter: junfei liang
> Priority: Minor
> Attachments: compated_discharger.png
>
>
> in one of online cluster(RS:16C72G, hbase version is 2.x) , cpu average
> usage is 30%, but cpu usage may above 80% occasionally. by a enchanced
> 'top -H' script, i find 'RS_COMPACTED_FILES_DISCHARGER' threads can use
> 50%+ cpu ( 10 * 80% ).
>
> !compated_discharger.png|width=1168,height=454!
>
> by jstack , we found most of stacks is at.
> "org.apache.hadoop.hbase.io.hfile.LruBlockCache#evictBlocksByHfileName"
> public int evictBlocksByHfileName(String hfileName) {
> int numEvicted = 0;
> for (BlockCacheKey key : map.keySet()) {
> if (key.getHfileName().equals(hfileName)) {
> if (evictBlock(key))
> ++numEvicted;
> }
> }
> if (victimHandler != null) {
> numEvicted += victimHandler.evictBlocksByHfileName(hfileName);
> }
> return numEvicted;
> }
>
> when close storefile, now we evict it's blocks from cache, but we have to
> traverse the whole blockcache to locate the block cached, and can lead to
> high cpu usage.
> do we need evict blockcache when close file, even for a small file ( size
> less than 10MB)? it's a lru block cache, the unused block will be
> automatically removed from cache when blockcache usage is high?
>
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