apache / commons-io / 543

88%

Pull #101

travis-ci

Improve the performance of the contentEquals() methods.

This change modifies the contentEquals() methods to internally buffer content into a byte/char array and to then do batch comparisons of those arrays using Arrays.equals instead of using a BufferedInputStream or BufferedReader and making use of the single byte/char read() methods.

This reduces the number of method invocations by a factor equal to the buffer size and avoids casting every byte read to an int and improves performance significantly.

The following table shows the performance increase over 1000 iterations of comparing 2 1GB InputStream of binary data (stored in memory to avoid I/O).  This test was performed on an EC2 M4.4XL host using Java 1.8.0.232 and there was a forced System.gc() between each iteration to avoid GC as a source of latency:

Average: 7236 to 858ms (8.43x speedup)
P50: 7224 to 856ms (8.44x speedup)
P90: 7249 to 860ms (8.43x speedup)
P99: 7410 to 913ms (8.12x speedup)
P100: 8330 to 1278ms (6.52x speedup)

The following table shows the performance increase over 1000 iterations of comparing 2 1GB Reader of character data (stored in memory to avoid I/O).  This test was performed on an EC2 M4.4XL host using Java 1.8.0.232 and there was a forced System.gc() between each iteration to avoid GC as a source of latency:

Average: 11281 to 1737ms (6.50x speedup)
P50: 11262 to 1735ms (6.49x speedup)
P90: 11292 to 1741ms (6.49x speedup)
P99: 11707 to 1774ms (6.60x speedup)
P100: 12176 to 1884ms (6.46x speedup)

24 of 24 new or added lines in 1 file covered. (100.0%)

5508 of 6152 relevant lines covered (89.53%)

21548.69 hits per line