[ https://issues.apache.org/jira/browse/CASSANDRA-3344?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sylvain Lebresne updated CASSANDRA-3344: ---------------------------------------- Attachment: 3344_v2.patch Right, that's indeed even simpler. Attaching v2 to do that instead. > Compaction throttling can be too slow > ------------------------------------- > > Key: CASSANDRA-3344 > URL: https://issues.apache.org/jira/browse/CASSANDRA-3344 > Project: Cassandra > Issue Type: Bug > Affects Versions: 0.8.6 > Reporter: Fabien Rousseau > Priority: Minor > Fix For: 0.8.8, 1.0.1 > > Attachments: 001-CASSANDRA-3344.patch, 3344.patch, 3344_v2.patch > > > Compaction throttling needs to know how many active compactions are running > (to divide bandwith for each active compaction). > The way active compaction is counted can be broken because it counts the > number of active threads in the executor BUT the thread starts by acquiring a > lock. > If the lock can't be acquired immediately : the thread is seen as "active" > but does not participate in IO operations. > The case can happen when major compaction are triggered (major compaction > acquire a write lock, while minor compactions acquire a read lock). > Having compaction througput to 16Mb/s, we observed is the following (two > times) : > - only 1 active compaction (a long one for a few hours) starting at 16Mb/s, > then after some time running at 2Mb/s, thus taking a very long time to > complete > - many pending compactions > Using JMX and monitoring the stack trace of the compaction threads showed > that : > - 1 thread was effectively compacting > - 1 thread was waiting to acquire the write lock (due to a major compaction) > - 6 threads were waiting to acquire the read lock (probably due to the > thread above trying to acquire the write lock) > Attached is a proposed patch (very simple, not yet tested) which counts only > active compactions. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira