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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4264) live ratio limit 64.0 is way too low
Date Mon, 21 May 2012 21:18:41 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4264?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13280503#comment-13280503
] 

Jonathan Ellis commented on CASSANDRA-4264:
-------------------------------------------

So...  that's 8x3 bytes for the longs; even if we take just a 1-character string that's 25
bytes total for the values.  Plus 32 for the timestamps and 15 for the column names is 72
bytes of data.

Back of the envelope, overhead is going to be about 100 bytes per column and another 100 for
the row.  So 500:72 or about 7.

Something is wrong if you're seeing 80-120x.  You should dig into what MemoryMeter is doing.
                
> live ratio limit 64.0 is way too low
> ------------------------------------
>
>                 Key: CASSANDRA-4264
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4264
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.8.0
>         Environment: FreeBSD 8 - 64 bit
>            Reporter: Radim Kolar
>            Priority: Trivial
>         Attachments: patch-liveratio.txt
>
>
> Currently live ratio is limited to 64.0. This is way too low.
> WARN [MemoryMeter:1] Memtable.java (line 181) setting live ratio to maximum of 64 instead
of xxxx
> values seen in log are ofter larger than 64.0 limit. I propose to use 100.0 as new limit.
> ponto:(admin)log/cassandra>grep "to maximum of 64" system.log.1
>  WARN [MemoryMeter:1] 2012-02-03 00:00:19,444 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 64.9096047648211
>  WARN [MemoryMeter:1] 2012-02-08 00:00:17,379 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 68.81016452376322
>  WARN [MemoryMeter:1] 2012-02-08 00:00:32,358 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 88.49747308025415
>  WARN [MemoryMeter:1] 2012-02-09 00:00:08,448 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 76.2444888765154
>  WARN [MemoryMeter:1] 2012-02-10 18:18:52,677 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 142.22477982642255
>  WARN [MemoryMeter:1] 2012-02-20 00:00:53,753 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 88.19832386767173
>  WARN [MemoryMeter:1] 2012-03-02 10:41:00,232 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 419.9607495592804
>  WARN [MemoryMeter:1] 2012-03-07 14:13:15,141 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of Infinity
>  WARN [MemoryMeter:1] 2012-03-08 00:01:12,766 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 94.20215772717702
>  WARN [MemoryMeter:1] 2012-03-09 00:00:38,633 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 98.54003447121715
>  WARN [MemoryMeter:1] 2012-03-11 00:00:13,243 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 193.14262214179965
>  WARN [MemoryMeter:1] 2012-03-14 00:00:26,709 Memtable.java (line 181) setting live ratio
to maximum of 64 instead of 103.88360138951437 

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