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From "Vijay (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3611) Make checksum on a compressed blocks optional
Date Sun, 11 Dec 2011 18:46:41 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3611?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13167169#comment-13167169
] 

Vijay commented on CASSANDRA-3611:
----------------------------------

" This may already have been implied, but on reads it might make sense to support a percentage
checking chance similarly to read-repair "
- Sure

" Any measurements on relative cost of checksumming? "
- below are the hot methods... I believe this can be further optimized with CASSANDRA-3610

   sec.      %
1480.474 100.00   <Total>
756.717  51.11   crc32
387.767  26.19   <static>@0x54999 (<snappy-1.0.4.1-libsnappyjava.so>)
 54.814   3.70   org.apache.cassandra.io.compress.CompressedRandomAccessReader.<init>(java.lang.String,
org.apache.cassandra.io.compress.CompressionMetadata, boolean)
 46.676   3.15   org.apache.cassandra.io.util.RandomAccessReader.<init>(java.io.File,
int, boolean)
 45.697   3.09   Copy::pd_disjoint_words(HeapWord*, HeapWord*, unsigned long)
 39.417   2.66   memcpy
 36.931   2.49   <static>@0xd8e9 (<libpthread-2.5.so>)
 23.272   1.57   CompactibleFreeListSpace::block_size(const HeapWord*) const
 22.766   1.54   SpinPause
                
> Make checksum on a compressed blocks optional
> ---------------------------------------------
>
>                 Key: CASSANDRA-3611
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3611
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1
>
>
> Currently every uncompressed block is run against checksum algo, there is cpu overhead
in doing same... We might want to make it configurable/optional for some use cases which might
not require checksum all the time.

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