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https://issues.apache.org/jira/browse/LUCENE-10128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17422213#comment-17422213
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Julie Tibshirani commented on LUCENE-10128:
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Thanks for looking into this! A clarification for those following along: we
don't have evidence of a new perf bug or regression. Rather in LUCENE-10109 we
adjusted an HNSW parameter to be more realistic, and are seeing a big indexing
slowdown (which we expected).
> increased HNSW beam with causes large indexing perf regression
> --------------------------------------------------------------
>
> Key: LUCENE-10128
> URL: https://issues.apache.org/jira/browse/LUCENE-10128
> Project: Lucene - Core
> Issue Type: Task
> Reporter: Robert Muir
> Priority: Major
> Attachments:
> LUCENE-10128_remove_sparse_fixed_bitset_reflection.patch,
> Screen_Shot_2021-09-28_at_09.10.15.png
>
>
> Just opening a ticket in case there is anything we could/should do about it.
> Looking at Mike's nightly benchmarks, I see a large (like 4x) drop in
> indexing perf with vectors after LUCENE-10109.
> There's some new stuff in the top CPU offenders:
> {noformat}
> PERCENT CPU SAMPLES STACK
> 19.93% 821395 org.apache.lucene.util.VectorUtil#dotProduct()
> 13.80% 568786 org.apache.lucene.util.LongHeap#downHeap()
> 11.06% 455711
> org.apache.lucene.codecs.KnnVectorsWriter$VectorValuesMerger$MergerRandomAccess#vectorValue()
> 9.84% 405678 org.apache.lucene.util.LongHeap#upHeap()
> 6.72% 276931 java.util.concurrent.atomic.AtomicLong#get()
> 5.30% 218564 org.apache.lucene.util.LongHeap$2#lessThan()
> 2.69% 110872 java.util.Arrays#binarySearch0()
> 2.58% 106294 org.apache.lucene.util.hnsw.HnswGraph#search()
> 1.90% 78254 org.apache.lucene.util.LongHeap#push()
> {noformat}
> compared to before where the profile stacks looked like this:
> {noformat}
> PERCENT CPU SAMPLES STACK
> 13.58% 171575 org.apache.lucene.util.VectorUtil#dotProduct()
> 10.13% 127904 org.apache.lucene.util.LongHeap#downHeap()
> 9.84% 124257 org.apache.lucene.util.LongHeap#upHeap()
> 6.26% 79125 java.util.ArrayList#elementData()
> 4.34% 54831 java.util.Random#nextInt()
> 3.98% 50255 org.apache.lucene.util.BytesRefHash#equals()
> 3.69% 46594 org.apache.lucene.util.ByteBlockPool#allocSlice()
> 2.62% 33118 org.apache.lucene.util.BytesRefHash#findHash()
> 2.24% 28275
> org.apache.lucene.analysis.standard.StandardTokenizerImpl#getNextToken()
> 2.14% 27033
> org.apache.lucene.analysis.standard.StandardTokenizer#incrementToken()
> {noformat}
> At a glance, it seems to me that although some perf differences should be
> expected, merging itself may have become more costly. Maybe there is some
> stuff we can optimize about it.
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