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 optimization is not only needed within the JDK core library, but also by developers of basic class libraries and applications. This should be done by the C2 optimizer. ------------- PR Comment: https://git.openjdk.org/jdk/pull/26493#issuecomment-3125494530
