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https://issues.apache.org/jira/browse/CASSANDRA-1969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981381#action_12981381
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Vijay commented on CASSANDRA-1969:
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Update:
Reclaiming the space of the invalid cache objects gets complicated.... running
OOM (Native) is not within the GC control (until a full GC runs on the JVM
automatically, free space are not automatically/manually reclaimed), and I
couldn't find a clean way to free the native memory from Java.
Option 1 (Easier option): Set a hard limit on the Native memory which can be
allocated by the GC once it is full, load the Objects in cache in the Heap
Memory. Eventually the cache will be cleaned by GC (always staying within 2
limits hard- total objects cached and soft - total objects which can be cached
in the heap).
Option 2: Allocate chunks of memory in the native memory and reclame it when
they are needed. Example: when you need 25.5 K block always allocate 26K block
and once it is free allocate a new Object which is of the same size into the
cache (This is only if GC didn't reclaim the object, if reclaimed by GC
reassign memory native), this can be done using PhantomReference, 'if' enqued
then allocate new 'else' use the same block of memory.
> Use BB for row cache - To Improve GC performance.
> -------------------------------------------------
>
> Key: CASSANDRA-1969
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1969
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Environment: Linux and Mac
> Reporter: Vijay
> Assignee: Vijay
> Priority: Minor
> Attachments: BB_Cache-1945.png, JMX-Cache-1945.png,
> Old_Cahce-1945.png, POC-0001-Config-1945.txt,
> POC-0002-Update_existing-1945.txt, POC-0003-New_Cache_Providers-1945.txt
>
>
> Java BB.allocateDirect() will allocate native memory out of the JVM and will
> help reducing the GC pressure in the JVM with a large Cache.
> From some of the basic tests it shows around 50% improvement than doing a
> normal Object cache.
> In addition this patch provide the users an option to choose
> BB.allocateDirect or store everything in the heap.
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