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https://issues.apache.org/jira/browse/CASSANDRA-21075?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18045165#comment-18045165
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Dmitry Konstantinov edited comment on CASSANDRA-21075 at 12/15/25 2:13 PM:
---------------------------------------------------------------------------
[https://github.com/apache/cassandra/compare/trunk...netudima:cassandra:CASSANDRA-21075-trunk-experiments]
Initial microbenchmark results for a short (12 bytes) ASCII string:
Temurin-11.0.28+6
{code:java}
[java] Benchmark Mode
Cnt Score Error Units
[java] UTF8ValidatorBench.testOldBimorphic avgt
15 40.309 ± 3.404 ns/op
[java] UTF8ValidatorBench.testNewBimorphic avgt
15 13.775 ± 0.067 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicArray avgt
15 23.723 ± 2.159 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicArray avgt
15 10.708 ± 0.332 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicHeapByteBuffer avgt
15 44.297 ± 0.849 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicHeapByteBuffer avgt
15 13.497 ± 0.140 ns/op
{code}
Temurin-17.0.12+7
{code}
[java] UTF8ValidatorBench.testNewBimorphic avgt
15 11.405 ± 0.172 ns/op
[java] UTF8ValidatorBench.testOldBimorphic avgt
15 30.383 ± 0.696 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicArray avgt
15 18.528 ± 0.785 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicArray avgt
15 8.791 ± 0.070 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicHeapByteBuffer avgt
15 27.887 ± 0.161 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicHeapByteBuffer avgt
15 11.705 ± 0.213 ns/op
{code}
was (Author: dnk):
[https://github.com/apache/cassandra/compare/trunk...netudima:cassandra:CASSANDRA-21075-trunk-experiments]
Initial microbenchmark results for a short (12 bytes) ASCII string:
{code:java}
[java] Benchmark Mode
Cnt Score Error Units
[java] UTF8ValidatorBench.testOldBimorphic avgt
15 40.309 ± 3.404 ns/op
[java] UTF8ValidatorBench.testNewBimorphic avgt
15 13.775 ± 0.067 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicArray avgt
15 23.723 ± 2.159 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicArray avgt
15 10.708 ± 0.332 ns/op
[java] UTF8ValidatorBench.testOldMonomorphicHeapByteBuffer avgt
15 44.297 ± 0.849 ns/op
[java] UTF8ValidatorBench.testNewMonomorphicHeapByteBuffer avgt
15 13.497 ± 0.140 ns/op
{code}
> Optimize UTF8Validator.validate for ASCII prefixed Strings
> ----------------------------------------------------------
>
> Key: CASSANDRA-21075
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21075
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: CQL/Interpreter
> Reporter: Dmitry Konstantinov
> Assignee: Dmitry Konstantinov
> Priority: Normal
> Fix For: 5.x
>
> Attachments: before_cpu.html
>
>
> In my batch write test, UTF8 validation contributes 2.1% of CPU:
> [^before_cpu.html]
> In UTF8Validator.validate we can apply the same optimization as Guava and JDK
> does: they use a plain loop to check if it is ASCII symbol before going into
> more complicated UTF8 parsing:
> *
> [https://github.com/google/guava/blob/master/guava/src/com/google/common/base/Utf8.java#L123]
> {code:java}
> for (int i = off; i < end; i++) {
> if (bytes[i] < 0) {
> return isWellFormedSlowPath(bytes, i, end);
> }
> } {code}
> * java.lang.StringCoding#decodeUTF8
> {code:java}
> // ascii-bais, which has a relative impact to the non-ascii-only bytes
> if (COMPACT_STRINGS && !hasNegatives(src, sp, len))
> return resultCached().with(Arrays.copyOfRange(src, sp, sp + len),
> LATIN1);
> return decodeUTF8_0(src, sp, len, doReplace);
> where:
> public static boolean hasNegatives(byte[] ba, int off, int len) {
> for (int i = off; i < off + len; i++) {
> if (ba[i] < 0) {
> return true;
> }
> }
> return false;
> } {code}
> See also:
> [https://lemire.me/blog/2018/10/16/validating-utf-8-bytes-java-edition/]
> Additionally, using of ValueAccessor is not a free lunch and by avoiding it
> we can get extra boost, especially in non-monomorphic cases.
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