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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-2142) Add "reduce memory usage because I tuned things poorly" feature
Date Wed, 09 Feb 2011 00:46:57 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-2142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-2142:
--------------------------------------

    Attachment: 2142-v3.txt

v3 makes the fraction to reduce cache capacities to configurable, and expands comments in
.yamls:

{noformat}
# emergency pressure valve: each time heap usage after a full (CMS)
# garbage collection is above this fraction of the max, Cassandra will
# flush the largest memtables.
#
# Set to 1.0 to disable.  Setting this lower than
# CMSInitiatingOccupancyFraction is not likely to be useful.
#
# RELYING ON THIS AS YOUR PRIMARY TUNING MECHANISM WILL WORK POORLY:
# it is most effective under light to moderate load, or read-heavy
# workloads; under truly massive write load, it will often be too
# little, too late.
flush_largest_memtables_at: 0.75

# emergency pressure valve #2: the first time heap usage after a full
# (CMS) garbage collection is above this fraction of the max,
# Cassandra will reduce cache maximum _capacity_ to the given fraction
# of the current _size_.  Should usually be set substantially above
# flush_largest_memtables_at, since that will have less long-term
# impact on the system.
#
# Set to 1.0 to disable.  Setting this lower than
# CMSInitiatingOccupancyFraction is not likely to be useful.
reduce_cache_sizes_at: 0.9
reduce_cache_capacity_to: 0.6
{noformat}

> Add "reduce memory usage because I tuned things poorly" feature
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-2142
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2142
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>              Labels: ponies
>             Fix For: 0.7.1
>
>         Attachments: 2142-v2.txt, 2142-v3.txt, 2142.txt
>
>
> Users frequently create too many columnfamilies, set the memtable thresholds too high
(or adjust throughput while ignoring operations), and/or set caching thresholds too high.
 Then their server OOMs and they tell their friends Cassandra sucks.

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