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From "Brandon Williams (Commented) (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-2893) Add row-level isolation
Date Thu, 22 Dec 2011 01:33:30 GMT


Brandon Williams commented on CASSANDRA-2893:

Maybe a chart isn't the best way to look at this.  First, let me note that I mislabeled the
X axis, this is _micro_seconds since I measured from cfhistograms to avoid any network interference,
so the differences are smaller than I originally implied (and may explain the throughput similarity
since network latency would dominate.)

Let's look at this statistically (as derived from the histogram data) instead.

h4. Non-contended
|10th %|5|5|
|25th %|6|7|
|50th %|8|8|
|75th %|10|10|
|95th %|42|42|
|99th %|103|103|

h4. Contended
|10th %|6|8|
|25th %|7|10|
|50th %|8|12|
|75th %|12|17|
|95th %|42|72|
|99th %|103|124|

Non-contended is almost exactly the same in every way.  Things begin to differ with a contended
row, but nothing I would call twice as bad.
> Add row-level isolation
> -----------------------
>                 Key: CASSANDRA-2893
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.1
>         Attachments: 0001-Move-deletion-infos-into-ISortedColumns-v2.patch, 0001-Move-deletion-infos-into-ISortedColumns.patch,
0002-Make-memtable-use-CF.addAll-v2.patch, 0002-Make-memtable-use-CF.addAll.patch, 0003-Add-AtomicSortedColumn-and-snapTree-v2.patch,
0003-Add-AtomicSortedColumn-and-snapTree.patch, latency-plain.svg, latency.svg, snaptree-0.1-SNAPSHOT.jar
> This could be done using an the atomic ConcurrentMap operations from the Memtable and
something like to replace the ConcurrentSkipListMap
in ThreadSafeSortedColumns.  The trick is that pcollections does not provide a SortedMap,
so we probably need to write our own.
> Googling [persistent sortedmap] I found
(in scala) and Structures-Maps.

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