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Posted to commits@cassandra.apache.org by "Branimir Lambov (JIRA)" <ji...@apache.org> on 2014/08/25 15:11:59 UTC
[jira] [Commented] (CASSANDRA-7039) DirectByteBuffer compatible LZ4
methods
[ https://issues.apache.org/jira/browse/CASSANDRA-7039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14109088#comment-14109088 ]
Branimir Lambov commented on CASSANDRA-7039:
--------------------------------------------
Patch up for review on
https://github.com/jpountz/lz4-java/issues/49
> DirectByteBuffer compatible LZ4 methods
> ---------------------------------------
>
> Key: CASSANDRA-7039
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7039
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Assignee: Branimir Lambov
> Priority: Minor
> Labels: performance
> Fix For: 3.0
>
>
> As we move more things off-heap, it's becoming more and more essential to be able to use DirectByteBuffer (or native pointers) in various places. Unfortunately LZ4 doesn't currently support this operation, despite being JNI based - this means we both have to perform unnecessary copies to de/compress data from DBB, but also we can stall GC as any JNI method operating over a java array using the GetPrimitiveArrayCritical enters a critical section that prevents GC for its duration. This means STWs will be at least as long any running compression/decompression (and no GC will happen until they complete, so it's additive).
> We should temporarily fork (and then resubmit upstream) jpountz-lz4 to support operating over a native pointer, so that we can pass a DBB or a raw pointer we have allocated ourselves. This will help improve performance when flushing the new offheap memtables, as well as enable us to implement CASSANDRA-6726 and finish CASSANDRA-4338.
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