[GitHub] [hadoop-ozone] runzhiwang edited a comment on pull request #1028: HDDS-3735. Improve SCM performance with 3.7% by remove unnecessary lock and unlock

[GitBox <gi...@apache.org>]

runzhiwang edited a comment on pull request #1028:
URL: https://github.com/apache/hadoop-ozone/pull/1028#issuecomment-647830265


   @elek Thanks for review. You are right, if the write code like following, maybe after  `currentInfo.setState(newState)` and before `currentInfo.setOwner(owner)`, we read the currentInfo, so we read a half write ContainerInfo. 
   ```
   lock.writeLock().lock();
   final ContainerInfo currentInfo = containerMap.get(containerID);
   currentInfo.setState(newState);
   currentInfo.setOwner(owner);
   lock.writeLock().unlock();
   ```
   
   I think we can avoid this by the following code. Though write become more complicated because it needs to new an object, but read is pretty more than write, so it's worth. What do you think ?
   ```
   lock.writeLock().lock();
   final ContainerInfo currentInfo = containerMap.get(containerID);
   ContainerInfo newInfo = new ContainerInfo(currentInfo);
   newInfo.setState(newState);
   newInfo.setOwner(owner);
   containerMap.put(containerID, newInfo);
   lock.writeLock().unlock();
   ```


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