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From "Henry Robinson (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4456: Change query exec state lock to a reader-writer lock
Date Wed, 09 Nov 2016 21:40:04 GMT
Henry Robinson has posted comments on this change.

Change subject: IMPALA-4456: Change query_exec_state_lock_ to a reader-writer lock
......................................................................


Patch Set 2:

(4 comments)

http://gerrit.cloudera.org:8080/#/c/5021/2//COMMIT_MSG
Commit Message:

PS2, Line 11: to
with


PS2, Line 13: This can reduce the amount of lock contention on this and translates
            : to big wins both in terms of performance and scalability.
            : 
            : Please refer the JIRA for more information.
Quantify what "big win" means.


http://gerrit.cloudera.org:8080/#/c/5021/2/be/src/service/impala-server.h
File be/src/service/impala-server.h:

Line 673:   /// acquisition order.
Update comment with expected read and write usage, and also update class comment if locking
order is different for reader and writer locks.


http://gerrit.cloudera.org:8080/#/c/5021/2/be/src/util/rw_lock.h
File be/src/util/rw_lock.h:

PS2, Line 25: class ReadWriteLock {
            :  public:
            :   ReadWriteLock() {}
            : 
            :   // Reader lock functions.
            :   void ReadAcquire() { l.ReadAcquire(); }
            :   void ReadRelease() { l.ReadRelease(); }
            : 
            :   // Writer lock functions.
            :   void WriteAcquire() { l.WriteAcquire(); }
            :   void WriteRelease() { l.WriteRelease(); }
            : 
            :  private:
            :   base::subtle::ReadWriteLock l;
            : 
            :   DISALLOW_COPY_AND_ASSIGN(ReadWriteLock);
            : };
Why does this class need to exist?


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Gerrit-MessageType: comment
Gerrit-Change-Id: I790a95e7179f07aa7ba188d5422c5e054353ba0b
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Sailesh Mukil <sailesh@cloudera.com>
Gerrit-Reviewer: Henry Robinson <henry@cloudera.com>
Gerrit-HasComments: Yes

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