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https://issues.apache.org/jira/browse/CASSANDRA-7282?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14103866#comment-14103866
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Joshua McKenzie commented on CASSANDRA-7282:
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Some interesting results on the
[99.9th|http://riptano.github.io/cassandra_performance/graph_v3/graph.html?stats=stats.7282.defaults.json&metric=99.9th_latency&operation=1_write&smoothing=1&show_aggregates=true&xmin=0&xmax=688.16&ymin=0&ymax=1600]
and
[max|http://riptano.github.io/cassandra_performance/graph_v3/graph.html?stats=stats.7282.defaults.json&metric=max_latency&operation=1_write&smoothing=1&show_aggregates=true&xmin=0&xmax=688.16&ymin=0&ymax=3000]
on write latency. While their aggregated values look better on the new
non-blocking hashordered map there look to be more outliers. Any ideas on why
that might be [~benedict]? 95th and 99th shows pretty [marked
improvement|http://riptano.github.io/cassandra_performance/graph_v3/graph.html?stats=stats.7282.defaults.json&metric=99th_latency&operation=1_write&smoothing=1&show_aggregates=true&xmin=0&xmax=688.16&ymin=0&ymax=140]
so the differential looks to be on the extremes only.
Either way - I'll be very interested to see the results of the test w/memtable
and row size changes.
> Faster Memtable map
> -------------------
>
> Key: CASSANDRA-7282
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7282
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Labels: performance
> Fix For: 3.0
>
>
> Currently we maintain a ConcurrentSkipLastMap of DecoratedKey -> Partition in
> our memtables. Maintaining this is an O(lg(n)) operation; since the vast
> majority of users use a hash partitioner, it occurs to me we could maintain a
> hybrid ordered list / hash map. The list would impose the normal order on the
> collection, but a hash index would live alongside as part of the same data
> structure, simply mapping into the list and permitting O(1) lookups and
> inserts.
> I've chosen to implement this initial version as a linked-list node per item,
> but we can optimise this in future by storing fatter nodes that permit a
> cache-line's worth of hashes to be checked at once, further reducing the
> constant factor costs for lookups.
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