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https://issues.apache.org/jira/browse/CASSANDRA-7438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14234696#comment-14234696
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Robert Stupp edited comment on CASSANDRA-7438 at 12/4/14 10:20 PM:
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Just pushed some OHC additions to github:
* key-iterator (used by CacheService class to invalidate column families)
* (de)serialization of cache content to disk using direct I/O from off-heap.
Means that the row cache content does not need to go though the heap for
serialization and deserialization. Compression should also be possible in
off-heap using the static methods in Snappy class since these expect direct
buffers so there's nearly no pressure for that on the heap. Background: the
implementation basically "lies" the address and length of the cache entry into
DirectByteBuffer class so FileChannel is able to read into it/write from it.
edit: s/hash/cache/
was (Author: snazy):
Just pushed some OHC additions to github:
* key-iterator (used by CacheService class to invalidate column families)
* (de)serialization of cache content to disk using direct I/O from off-heap.
Means that the row cache content does not need to go though the heap for
serialization and deserialization. Compression should also be possible in
off-heap using the static methods in Snappy class since these expect direct
buffers so there's nearly no pressure for that on the heap. Background: the
implementation basically "lies" the address and length of the hash entry into
DirectByteBuffer class so FileChannel is able to read into it/write from it.
> Serializing Row cache alternative (Fully off heap)
> --------------------------------------------------
>
> Key: CASSANDRA-7438
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7438
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Environment: Linux
> Reporter: Vijay
> Assignee: Vijay
> Labels: performance
> Fix For: 3.0
>
> Attachments: 0001-CASSANDRA-7438.patch, tests.zip
>
>
> Currently SerializingCache is partially off heap, keys are still stored in
> JVM heap as BB,
> * There is a higher GC costs for a reasonably big cache.
> * Some users have used the row cache efficiently in production for better
> results, but this requires careful tunning.
> * Overhead in Memory for the cache entries are relatively high.
> So the proposal for this ticket is to move the LRU cache logic completely off
> heap and use JNI to interact with cache. We might want to ensure that the new
> implementation match the existing API's (ICache), and the implementation
> needs to have safe memory access, low overhead in memory and less memcpy's
> (As much as possible).
> We might also want to make this cache configurable.
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