On Mon, 3 May 2021 20:33:23 GMT, Brian Burkhalter <bpb@openjdk.org> wrote:
Please consider this request to override the `java.io.InputStream` methods `readAllBytes()` and `readNBytes(int)` in `FileInputStream` with more performant implementations. The method overrides attempt to read all requested bytes into a single array of the required size rather than composing the result from a sequence of smaller arrays. An example of the performance improvements is as follows.
**readAllBytes** Before
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readAllBytesFileInputStream 1000000 thrpt 20 2412.031 ± 7.309 ops/s ReadAllBytes.readAllBytesFileInputStream 10000000 thrpt 20 212.181 ± 0.369 ops/s ReadAllBytes.readAllBytesFileInputStream 100000000 thrpt 20 19.860 ± 0.048 ops/s ReadAllBytes.readAllBytesFileInputStream 1000000000 thrpt 20 1.298 ± 0.183 ops/s
After
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readAllBytesFileInputStream 1000000 thrpt 20 8218.473 ± 43.425 ops/s ReadAllBytes.readAllBytesFileInputStream 10000000 thrpt 20 302.781 ± 1.273 ops/s ReadAllBytes.readAllBytesFileInputStream 100000000 thrpt 20 22.461 ± 0.084 ops/s ReadAllBytes.readAllBytesFileInputStream 1000000000 thrpt 20 1.502 ± 0.003 ops/s
**readNBytes**
`N = file_size / 2`
Before
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readHalfBytesFileInputStream 1000000 thrpt 20 5585.500 ± 153.353 ops/s ReadAllBytes.readHalfBytesFileInputStream 10000000 thrpt 20 436.164 ± 1.104 ops/s ReadAllBytes.readHalfBytesFileInputStream 100000000 thrpt 20 40.167 ± 0.141 ops/s ReadAllBytes.readHalfBytesFileInputStream 1000000000 thrpt 20 3.291 ± 0.211 ops/s
After
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readHalfBytesFileInputStream 1000000 thrpt 20 15463.210 ± 66.045 ops/s ReadAllBytes.readHalfBytesFileInputStream 10000000 thrpt 20 561.752 ± 0.951 ops/s ReadAllBytes.readHalfBytesFileInputStream 100000000 thrpt 20 45.043 ± 0.102 ops/s ReadAllBytes.readHalfBytesFileInputStream 1000000000 thrpt 20 4.629 ± 0.035 ops/s
This pull request has now been integrated. Changeset: da4dfde7 Author: Brian Burkhalter <bpb@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/da4dfde71a176d2b8401782178e854d4c924... Stats: 244 lines in 4 files changed: 238 ins; 1 del; 5 mod 8264777: Overload optimized FileInputStream::readAllBytes Reviewed-by: dfuchs, alanb ------------- PR: https://git.openjdk.java.net/jdk/pull/3845