On Sun, 27 Jul 2025 12:36:20 GMT, Philippe Marschall <d...@openjdk.org> wrote:
> Use `JavaLangAccess::uncheckedNewStringNoRepl` in `MemorySegment::getString` > to avoid byte[] allocation in the String constructor. > > Fall back to the old code in the case of malformed input to get replacement > characters as per Javadoc API specification. The existing tests in > `TestStringEncoding` seem sufficient to me. > > I ran the tier1 test suite and it passes. > > For performance analysis I ran. > > make test > TEST="micro:org.openjdk.bench.java.lang.foreign.ToJavaStringTest" > MICRO="OPTIONS=-prof gc" > > on an AMD Ryzen 7 PRO 5750GE. > > These are the formatted results, the current master is the line on top, this > feature branch is the line below. We can see an improvement in throughput > driven by a reduction in allocation. > > > Benchmark (size) Mode Cnt > Score Error Units > > ToJavaStringTest.panama_readString 5 avgt 30 > 18.996 ± 0.044 ns/op > ToJavaStringTest.panama_readString 5 avgt 30 > 13.851 ± 0.028 ns/op > > ToJavaStringTest.panama_readString 20 avgt 30 > 23.570 ± 0.050 ns/op > ToJavaStringTest.panama_readString 20 avgt 30 > 18.401 ± 0.069 ns/op > > ToJavaStringTest.panama_readString 100 avgt 30 > 32.094 ± 0.207 ns/op > ToJavaStringTest.panama_readString 100 avgt 30 > 24.427 ± 0.112 ns/op > > ToJavaStringTest.panama_readString 200 avgt 30 > 43.029 ± 0.185 ns/op > ToJavaStringTest.panama_readString 200 avgt 30 > 31.914 ± 0.064 ns/op > > ToJavaStringTest.panama_readString 451 avgt 30 > 81.145 ± 0.403 ns/op > ToJavaStringTest.panama_readString 451 avgt 30 > 58.975 ± 0.233 ns/op > > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 5 avgt 30 > 72.000 ± 0.001 B/op > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 5 avgt 30 > 48.000 ± 0.001 B/op > > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 20 avgt 30 > 104.000 ± 0.001 B/op > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 20 avgt 30 > 64.000 ± 0.001 B/op > > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 100 avgt 30 > 264.000 ± 0.001 B/op > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 100 avgt 30 > 144.000 ± 0.001 B/op > > ToJavaStringTest.panama_readString:gc.alloc.rate.norm 200 avgt ... This pull request has now been integrated. Changeset: 8f11d83a Author: Philippe Marschall <philippe.marsch...@gmail.com> Committer: Jaikiran Pai <j...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/8f11d83a0126f8179d72e714595588b631e6451d Stats: 20 lines in 1 file changed: 16 ins; 0 del; 4 mod 8362893: Improve performance for MemorySegment::getString Reviewed-by: pminborg, mcimadamore ------------- PR: https://git.openjdk.org/jdk/pull/26493
