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https://issues.apache.org/jira/browse/CASSANDRA-4038?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13423959#comment-13423959
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Pavel Yaskevich commented on CASSANDRA-4038:
--------------------------------------------
bq. Have you done any profiling to see if this actually is cheaper than the
fixed window size? Specifically I'm worried about receiveTiming becoming more
expensive.
Yes, I did a few profiling tests and I see ~30 ms degradation in receiveTiming
speed inserting 100000 latency records (increased UPDATES_PER_INTERVAL value to
be fare with the test).
> Investigate improving the dynamic snitch with reservoir sampling
> ----------------------------------------------------------------
>
> Key: CASSANDRA-4038
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4038
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Brandon Williams
> Assignee: Pavel Yaskevich
> Fix For: 1.2
>
> Attachments: CASSANDRA-4038.patch
>
>
> Dsnitch's UPDATES_PER_INTERVAL and WINDOW_SIZE are chosen somewhat
> arbitrarily. A better fit may be something similar to Metric's
> ExponentiallyDecayingSample, where more recent information is weighted
> heavier than past information, and reservoir sampling would also be an
> efficient way of keeping a statistically significant sample rather than
> refusing updates after UPDATES_PER_INTERVAL and only keeping WINDOW_SIZE
> amount.
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