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From "Jonathan Ellis (Commented) (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-3610) Checksum improvement for CompressedRandomAccessReader
Date Thu, 22 Dec 2011 20:47:31 GMT


Jonathan Ellis commented on CASSANDRA-3610:

Why would increasing heap size make the Native version perform *worse*? Something seems fishy

Also: GC overhead is part of "real world" workloads, so increasing heap size so that heap
is large enough to complete small runs w/ no GC seems like stacking the deck. :)
> Checksum improvement for CompressedRandomAccessReader
> -----------------------------------------------------
>                 Key: CASSANDRA-3610
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1
>         Environment: JVM
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1
>         Attachments: 0001-use-pure-java-CRC32-v2.patch, 0001-use-pure-java-CRC32.patch
> When compression is on, Currently we see checksum taking up about 40% of the CPU more
than snappy library.
> Looks like hadoop solved it by implementing their own checksum, we can either use it
or implement something like that.
> in our test env it provided 50% improvement over native implementation which uses jni
to call the OS.

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