On Fri, 15 Jan 2021 14:33:19 GMT, Claes Redestad <redes...@openjdk.org> wrote:
> The `StringCoding.resultCached` mechanism is used to remove the allocation of > a `StringCoding.Result` object on potentially hot paths used in some `String` > constructors. Using a `ThreadLocal` has overheads though, and the overhead > got a bit worse after JDK-8258596 which addresses a leak by adding a > `SoftReference`. > > This patch refactors much of the decode logic back into `String` and gets rid > of not only the `Result` cache, but the `Result` class itself along with the > `StringDecoder` class and cache. > > Microbenchmark results: > Baseline > > Benchmark (charsetName) Mode Cnt > Score Error Units > decodeCharset US-ASCII avgt 15 > 193.043 ± 8.207 ns/op > decodeCharset:·gc.alloc.rate.norm US-ASCII avgt 15 > 112.009 ± 0.001 B/op > decodeCharset ISO-8859-1 avgt 15 > 164.580 ± 6.514 ns/op > decodeCharset:·gc.alloc.rate.norm ISO-8859-1 avgt 15 > 112.009 ± 0.001 B/op > decodeCharset UTF-8 avgt 15 > 328.370 ± 18.420 ns/op > decodeCharset:·gc.alloc.rate.norm UTF-8 avgt 15 > 224.019 ± 0.002 B/op > decodeCharset MS932 avgt 15 > 328.870 ± 20.056 ns/op > decodeCharset:·gc.alloc.rate.norm MS932 avgt 15 > 232.020 ± 0.002 B/op > decodeCharset ISO-8859-6 avgt 15 > 193.603 ± 12.305 ns/op > decodeCharset:·gc.alloc.rate.norm ISO-8859-6 avgt 15 > 112.010 ± 0.001 B/op > decodeCharsetName US-ASCII avgt 15 > 209.454 ± 9.040 ns/op > decodeCharsetName:·gc.alloc.rate.norm US-ASCII avgt 15 > 112.009 ± 0.001 B/op > decodeCharsetName ISO-8859-1 avgt 15 > 188.234 ± 7.533 ns/op > decodeCharsetName:·gc.alloc.rate.norm ISO-8859-1 avgt 15 > 112.009 ± 0.001 B/op > decodeCharsetName UTF-8 avgt 15 > 399.463 ± 12.437 ns/op > decodeCharsetName:·gc.alloc.rate.norm UTF-8 avgt 15 > 224.019 ± 0.003 B/op > decodeCharsetName MS932 avgt 15 > 358.839 ± 15.385 ns/op > decodeCharsetName:·gc.alloc.rate.norm MS932 avgt 15 > 208.017 ± 0.003 B/op > decodeCharsetName ISO-8859-6 avgt 15 > 162.570 ± 7.090 ns/op > decodeCharsetName:·gc.alloc.rate.norm ISO-8859-6 avgt 15 > 112.009 ± 0.001 B/op > decodeDefault N/A avgt 15 > 316.081 ± 11.101 ns/op > decodeDefault:·gc.alloc.rate.norm N/A avgt 15 > 224.019 ± 0.002 B/op > > Patched: > Benchmark (charsetName) Mode Cnt > Score Error Units > decodeCharset US-ASCII avgt 15 > 159.153 ± 6.082 ns/op > decodeCharset:·gc.alloc.rate.norm US-ASCII avgt 15 > 112.009 ± 0.001 B/op > decodeCharset ISO-8859-1 avgt 15 > 134.433 ± 6.203 ns/op > decodeCharset:·gc.alloc.rate.norm ISO-8859-1 avgt 15 > 112.009 ± 0.001 B/op > decodeCharset UTF-8 avgt 15 > 297.234 ± 21.654 ns/op > decodeCharset:·gc.alloc.rate.norm UTF-8 avgt 15 > 224.019 ± 0.002 B/op > decodeCharset MS932 avgt 15 > 311.583 ± 16.445 ns/op > decodeCharset:·gc.alloc.rate.norm MS932 avgt 15 > 208.018 ± 0.002 B/op > decodeCharset ISO-8859-6 avgt 15 > 156.216 ± 6.522 ns/op > decodeCharset:·gc.alloc.rate.norm ISO-8859-6 avgt 15 > 112.010 ± 0.001 B/op > decodeCharsetName US-ASCII avgt 15 > 180.752 ± 9.411 ns/op > decodeCharsetName:·gc.alloc.rate.norm US-ASCII avgt 15 > 112.010 ± 0.001 B/op > decodeCharsetName ISO-8859-1 avgt 15 > 156.170 ± 8.003 ns/op > decodeCharsetName:·gc.alloc.rate.norm ISO-8859-1 avgt 15 > 112.010 ± 0.001 B/op > decodeCharsetName UTF-8 avgt 15 > 370.337 ± 22.199 ns/op > decodeCharsetName:·gc.alloc.rate.norm UTF-8 avgt 15 > 224.019 ± 0.001 B/op > decodeCharsetName MS932 avgt 15 > 312.589 ± 15.067 ns/op > decodeCharsetName:·gc.alloc.rate.norm MS932 avgt 15 > 208.018 ± 0.002 B/op > decodeCharsetName ISO-8859-6 avgt 15 > 173.205 ± 9.647 ns/op > decodeCharsetName:·gc.alloc.rate.norm ISO-8859-6 avgt 15 > 112.009 ± 0.001 B/op > decodeDefault N/A avgt 15 > 303.459 ± 16.452 ns/op > decodeDefault:·gc.alloc.rate.norm N/A avgt 15 > 224.019 ± 0.001 B/op > > Most variants improve. There's a small added overhead in `String charsetName` > variants for some charsets such as `ISO-8859-6` that benefited slightly from > the `StringDecoder` cache due avoiding a lookup, but most variants are not > helped by this cache and instead see a significant gain from skipping that > step. `Charset` variants don't need a lookup and improve across the board. > > Another drawback is that we need to cram more logic into `String` to bypass > the `StringCoding.Result` indirection - but getting rid of two commonly used > `ThreadLocal` caches and most cases getting a bit better raw throughput in > the process I think more than enough makes up for that. > > Testing: tier1-4 This pull request has now been integrated. Changeset: 58ceb254 Author: Claes Redestad <redes...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/58ceb254 Stats: 2093 lines in 5 files changed: 971 ins; 1093 del; 29 mod 8259842: Remove Result cache from StringCoding Reviewed-by: naoto, plevart, rriggs ------------- PR: https://git.openjdk.java.net/jdk/pull/2102
