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https://issues.apache.org/jira/browse/CASSANDRA-15389?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17013294#comment-17013294
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Benedict Elliott Smith edited comment on CASSANDRA-15389 at 1/11/20 12:44 AM:
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very nice!
If we change the order of parameter provision to the {{BiLongAccumulator}}, we
can (if we want) do the same trick of just supplying
{{accumulate(LongAccumulator::apply, accumulator, initialValue)}} to keep only
one implementation without the extra (admittedly minor) obfuscation.
I still need to double check the fine details of a couple of the methods, but I
think we're pretty much close to done here.
was (Author: benedict):
very nice!
If we change the order of parameter provision to the BiLongAccumulator, we can
(if we want) do the same trick of just supplying
{{accumulate(LongAccumulator::apply, accumulator, initialValue)}} to keep only
one implementation without the extra (admittedly minor) obfuscation.
I still need to double check the fine details of a couple of the methods, but I
think we're pretty much close to done here.
> 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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