private void run()

in src/main/java/com/uber/rss/tools/FsyncPerfTest.java [91:148]
47 lines of code
4 McCabe index (conditional complexity)

    private void run() {
        Arrays.stream(fileStreams).parallel().forEach(stream -> {
            long writeBytes = 0;

            for (int i = 0; i < numWrites; i++) {
                int valueIndex = random.nextInt(testValues.length);
                byte[] bytes = testValues[valueIndex];
                try {
                    totalOperationCount.incrementAndGet();
                    writeBytes += bytes.length;

                    long startTime = System.nanoTime();
                    stream.write(bytes);
                    totalWriteTime.addAndGet(System.nanoTime() - startTime);

                    startTime = System.nanoTime();
                    stream.flush();
                    totalFlushTime.addAndGet(System.nanoTime() - startTime);

                    startTime = System.nanoTime();
                    stream.getFD().sync();
                    long fsyncDuration = System.nanoTime() - startTime;
                    totalFsyncTime.addAndGet(fsyncDuration);

                    fsyncMillisValues[fsyncMillisValuesIndex.getAndIncrement()] = TimeUnit.NANOSECONDS.toMillis(fsyncDuration);
                } catch (IOException e) {
                    throw new RuntimeException("Failed to write file", e);
                }
            }

            logger.info(String.format("Finished writing file: %s bytes", writeBytes));
        });

        logger.info(String.format("Total operation: %s, total write seconds: %s, flush: %s, fsync: %s, average write milliseconds: %s, flush: %s, fsync: %s",
                totalOperationCount.get(),
                TimeUnit.NANOSECONDS.toSeconds(totalWriteTime.get()),
                TimeUnit.NANOSECONDS.toSeconds(totalFlushTime.get()),
                TimeUnit.NANOSECONDS.toSeconds(totalFsyncTime.get()),
                TimeUnit.NANOSECONDS.toMillis(totalWriteTime.get()/totalOperationCount.get()),
                TimeUnit.NANOSECONDS.toMillis(totalFlushTime.get()/totalOperationCount.get()),
                TimeUnit.NANOSECONDS.toMillis(totalFsyncTime.get()/totalOperationCount.get())));

        EmpiricalDistribution fsyncMillisDistribution = new EmpiricalDistribution();
        fsyncMillisDistribution.load(fsyncMillisValues);

        DescriptiveStatistics stats = new DescriptiveStatistics();
        for (double v: fsyncMillisValues) {
            stats.addValue(v);
        }

        stats.getPercentile(50);

        logger.info(String.format("fsync duration (milliseconds): P50: %s, P95: %s, P99: %s, max: %s",
                stats.getPercentile(50),
                stats.getPercentile(95),
                stats.getPercentile(99),
                stats.getMax()));
    }