[jira] [Created] (HBASE-23277) CompactedHFilesDischarger may lead to high cpu usage

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

junfei liang created HBASE-23277:
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             Summary: 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
         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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