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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12731) Remove IndexInfo cache from FileIndexInfoRetriever.
Date Mon, 03 Oct 2016 12:31:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15542317#comment-15542317
] 

Robert Stupp commented on CASSANDRA-12731:
------------------------------------------

Nice catch, [~Yasuharu] !
I did some comparison myself and get similar improvements using the patch you provided so
I've setup a branch for CI. The branch also includes a temporary fix for the issue you've
also reported as CASSANDRA-12717.
||trunk|[branch|https://github.com/apache/cassandra/compare/trunk...snazy:12731-modified-trunk]|[testall|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-12731-modified-trunk-testall/lastSuccessfulBuild/]|[dtest|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-12731-modified-trunk-dtest/lastSuccessfulBuild/]


> Remove IndexInfo cache from FileIndexInfoRetriever.
> ---------------------------------------------------
>
>                 Key: CASSANDRA-12731
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12731
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Yasuharu Goto
>            Assignee: Yasuharu Goto
>         Attachments: screenshot-1.png, screenshot-2.png
>
>
> Hi guys.
> In the patch of CASSANDRA-11206 , I found that FileIndexInfoRetriever allocates a (potentially
very large) IndexInfo array (up to the number of IndexInfo in the RowIndexEntry has) as a
cache in every single read path.
> After some experiments using LargePartitionTest on my MacBook, I got results that show
that removing FileIndexInfoRetriever improves the performance for large partitions like below
(latencies reduced by 41% and by 45%).
> {noformat}
> // LargePartitionsTest.test_13_4G with cache by array
> INFO  [main] 2016-09-29 23:11:25,763 ?:? - SELECTs 1 for part=4194304k total=16384M took
94197 ms
> INFO  [main] 2016-09-29 23:12:50,914 ?:? - SELECTs 2 for part=4194304k total=16384M took
85151 ms
> // LargePartitionsTest.test_13_4G without cache
> INFO  [main] 2016-09-30 00:13:26,050 ?:? - SELECTs 1 for part=4194304k total=16384M took
55112 ms
> INFO  [main] 2016-09-30 00:14:12,132 ?:? - SELECTs 2 for part=4194304k total=16384M took
46082 ms
> {noformat}
> Code is [here|https://github.com/matope/cassandra/commit/86fb910a0e38f7520e1be40fb42f74a692f2ebce]
(based on trunk)
> Heap memory usage during running LargePartitionsTest (except for 8G test) with array
cache(original)
> !screenshot-1.png!
> Heap memory usage during running LargePartitionsTest (except for 8G test) without cache
> !screenshot-2.png!
> Of course, I have attempted to use some collection containers instead of a plain array.
But I could not recognize great improvement enough to justify using these cache mechanism
by them. (Unless I did some mistake or overlook about this test)
> || LargePartitionsTest.test_12_2G || SELECTs 1 (ms) || SELECTs 2 (ms) || Scan (ms) ||
> |Original (array) | 62736 | 48562 | 41540 |
> |ConcurrentHashMap | 47597 | 30854 | 18271 |
> |ConcurrentHashMap 2nd trial |44036|26895|17443|
> |LinkedHashCache (capacity=16, limit=10, fifo) 1st|42668|32165|17323|
> |LinkedHashCache (capacity=16, limit=10, fifo) 2nd|48863|28066|18053|
> |LinkedHashCache (capacity=16, limit=16, fifo) | 46979 | 29810 | 18620 |
> |LinkedHashCache (capacity=16, limit=10, lru) | 46456 | 29749 | 20311 |
> |No Cache | 47579 | 32480 | 18337 |
> |No Cache 2nd trial | 46534 | 27670 | 18700 |
> Code that I used for this comparison is [here|https://github.com/matope/cassandra/commit/e12fcac77f0f46bdf4104ef21c6454bfb2bb92d0].
LinkedHashCache is a simple fifo/lru cache that is extended by LinkedHashMap.
> Scan is a execution time to iterate through the large partition.
> So, in this issue, I'd like to propose to remove IndexInfo cache from FileIndexInfoRetriever
to improve the performance on large partitions.



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