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Posted to commits@cassandra.apache.org by "Blake Eggleston (Jira)" <ji...@apache.org> on 2019/10/30 22:39:00 UTC
[jira] [Updated] (CASSANDRA-15389) Minimize BTree iterator
allocations
[ https://issues.apache.org/jira/browse/CASSANDRA-15389?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Blake Eggleston updated CASSANDRA-15389:
----------------------------------------
Change Category: Performance
Complexity: Normal
Component/s: Local/Compaction
Fix Version/s: 4.0
Status: Open (was: Triage Needed)
> Minimize BTree iterator allocations
> -----------------------------------
>
> Key: CASSANDRA-15389
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15389
> Project: Cassandra
> Issue Type: Sub-task
> Components: Local/Compaction
> Reporter: Blake Eggleston
> Assignee: Blake Eggleston
> Priority: Normal
> Fix For: 4.0
>
>
> Allocations of BTree iterators contribute a lot amount of garbage to the compaction and read paths.
> This patch removes most btree iterator allocations on hot paths by:
> • using Row#apply where appropriate on frequently called methods (Row#digest, Row#validateData
> • adding BTree accumulate method. Like the apply method, this method walks the btree with a function that takes and returns a long argument, this eliminates iterator allocations without adding helper object allocations (BTreeRow#hasComplex, BTreeRow#hasInvalidDeletions, BTreeRow#dataSize, BTreeRow#unsharedHeapSizeExcludingData, Rows#collectStats, UnfilteredSerializer#serializedRowBodySize) as well as eliminating the allocation of helper objects in places where apply was used previously^[1]^.
> • Create map of columns in SerializationHeader, this lets us avoid allocating a btree search iterator for each row we serialize.
> These optimizations reduce garbage created during compaction by up to 13.5%
>
> [1] the memory test does measure memory allocated by lambdas capturing objects
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