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Vijay commented on CASSANDRA-3623:
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Pavel, it doesnt show the opposite it actually shows the time spent is 98% in
the snappy library and only 2% in the remaining part of the code. Where as in
the earlier case we spend 58% of the time in Snappy and rest in the other part
of the code. Snappy/decompression is definitely the bottleneck... all i am
saying is that now we are more efficient and thats the only bottleneck.
"Did you mean compressed instead of uncompressed here?"
Yes i ment compressed.
Plz try a test before and after the patch you will see what i am talking about,
I did run the cluster (before and after there isnt any other variable in play
here) test it for a long time and after this patch shows constat performance
and doesn't vary a lot (response times after the patch).
> 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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