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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] Created: (CASSANDRA-1954) Double-check or replace RRW memtable lock
Date Sat, 08 Jan 2011 03:35:45 GMT
Double-check or replace RRW memtable lock
-----------------------------------------

                 Key: CASSANDRA-1954
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1954
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
            Reporter: Stu Hood
            Priority: Minor
             Fix For: 0.7.1, 0.8


{quote}...when a Memtable reaches its threshold, up to (all) N write threads will often notice,
and race to acquire the writeLock in order to freeze the memtable. This means that we do way
more writeLock acquisitions than we need to...{quote}

See CASSANDRA-1930 for backstory, but adding double checking inside a read lock before trying
to re-entrantly acquire the writelock would eliminate most of these excess writelock acquisitions.

Alternatively, we should explore removing locking from these structures entirely, and replacing
the writeLock acquisition with a per-memtable counter of active threads.

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