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Vijay commented on CASSANDRA-3623:
----------------------------------
Regarding duplicates i was thinking of Creating duplicates in CMSF and having a
helper function to track it.
Regarding Hot Reads: (I tried before and you have to access the FD and caching
the initialized object didn't help), We do get something like 50% better
latencies by doing MMap'ed without copying the data. Snappy is 1.6% more
because there isn't any thing else holding up or any other over head.
Currently with this patch we dont have to copy any uncompressed data but the
CRAR will copy because we dont handle the DirectBB to snappy and that's made
possible by using MMapped IO.
> use MMapedBuffer in CompressedSegmentedFile.getSegment
> ------------------------------------------------------
>
> Key: CASSANDRA-3623
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3623
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 1.1
> Reporter: Vijay
> Assignee: Vijay
> Labels: compression
> Fix For: 1.1
>
> Attachments: 0001-MMaped-Compression-segmented-file-v2.patch,
> 0001-MMaped-Compression-segmented-file.patch,
> 0002-tests-for-MMaped-Compression-segmented-file-v2.patch
>
>
> CompressedSegmentedFile.getSegment seem to open a new file and doesnt seem to
> use the MMap and hence a higher CPU on the nodes and higher latencies on
> reads.
> This ticket is to implement the TODO mentioned in CompressedRandomAccessReader
> // TODO refactor this to separate concept of "buffer to avoid lots of read()
> syscalls" and "compression buffer"
> but i think a separate class for the Buffer will be better.
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