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Date: Tue, 22 Apr 2014 21:56:16 +0000 (UTC)
From: "Aleksey Yeschenko (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12704100.1395953392399.158941.1398203776175@arcas>
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Subject: [jira] [Commented] (CASSANDRA-6944) liveRatio jumps to max when
 Memtable is empty
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    [ https://issues.apache.org/jira/browse/CASSANDRA-6944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13977512#comment-13977512 ] 

Aleksey Yeschenko commented on CASSANDRA-6944:
----------------------------------------------

I say it's not a problem after CASSANDRA-6945 (in fact, this scenario was one of the reasons for 6945 in the first place). The new memtable would inherit both the live ratio and calculatedAt. So as soon as some data starts flowing into the memtable, the ratio will be recalculated. 64 will never stuck for long.

> liveRatio jumps to max when Memtable is empty
> ---------------------------------------------
>
>                 Key: CASSANDRA-6944
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6944
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: SUSE Linux Enterprise 11 (64-bit)
>            Reporter: Erik Hansen
>            Assignee: Aleksey Yeschenko
>            Priority: Minor
>              Labels: memtables
>
> liveRatio calculation on an empty memtable results in a value of Infinity since memtable.currentSize=0.  Infinity then gets capped at the liveRatio max of 64.
> {noformat}
> WARN [MemoryMeter:1] 2014-03-19 09:26:59,483 Memtable.java (line 441) setting live ratio to maximum of 64.0 instead of Infinity
> INFO [MemoryMeter:1] 2014-03-19 09:26:59,485 Memtable.java (line 452) CFS(Keyspace='system', ColumnFamily='compactions_in_progress') liveRatio is 64.0 (just-counted was 64.0).  calculation took 7ms for 0 cells
> {noformat}
> Jumping liveRatio to the max value based on an empty Memtable leads to more frequent flushing than may be necessary.
> CASSANDRA-4243 previously addressed this issue, but was resolved as fixed by CASSANDRA-3741.  It does not appear this issue has been fixed as of 2.0.5


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