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https://issues.apache.org/jira/browse/CASSANDRA-10529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14958281#comment-14958281
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Stefania commented on CASSANDRA-10529:
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I've removed the assertion, see patch attached.
h5. CI
http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-10529-3.0-dtest/
http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-10529-3.0-testall/
h5. cstar comparison
http://cstar.datastax.com/graph?command=one_job&stats=b38f2330-72ec-11e5-8625-0256e416528f&metric=op_rate&operation=2_read&smoothing=1&show_aggregates=true&xmin=0&xmax=44&ymin=0&ymax=161867.2
http://cstar.datastax.com/graph?command=one_job&stats=9279e6e0-72f0-11e5-a177-0256e416528f&metric=op_rate&operation=2_read&smoothing=1&show_aggregates=true&xmin=0&xmax=43.01&ymin=0&ymax=167997.5
I think the gains must be below the variance of cstar or there must be an issue
with the test parameters or environment; the patched mmap performs worse in
both cases but it shouldn't since we just removed an assertion.
> Channel.size() is costly, mutually exclusive, and on the critical path
> ----------------------------------------------------------------------
>
> Key: CASSANDRA-10529
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10529
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Benedict
> Assignee: Stefania
> Fix For: 3.0.0 rc2
>
>
> [~stefania_alborghetti] mentioned this already on another ticket, but I have
> lost track of exactly where. While benchmarking it became apparent this was a
> noticeable bottleneck for small in-memory workloads with few files,
> especially with RF=1. We should probably fix this soon, since it is trivial
> to do so, and the call is only to impose an assertion that our requested
> length is less than the file size. It isn't possible to safely memoize a
> value anywhere we can guarantee to be able to safely refer to it without some
> refactoring, so I suggest simply removing the assertion for now.
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