On Mon, 3 May 2021 20:33:23 GMT, Brian Burkhalter <b...@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 src/java.base/share/classes/java/io/FileInputStream.java line 342: > 340: > 341: private native long length() throws IOException; > 342: private native long position() throws IOException; Can you confirm that you've tested with special files? It's very likely that there will be cases where lseek will fail. ------------- PR: https://git.openjdk.java.net/jdk/pull/3845
