[ww520]

The statement, "The JVM and V8 are both fast enough to be almost negligible" is flawed. OS file system caching pretty much makes disk IO negligible, and the time spent in JVM and V8 are the majority of the time. The benchmark is consistent with the system behavior, showing the difference between JVM and V8 is not negligible but substantial.

[IsaacSchlueter]

The discrepancy in this benchmark is almost entirely copying the results of read(2) into a userspace buffer. OS caching is important, but it's not the whole story here.

As some other commenters pointed out, if you pre-load the file contents, the discrepancy goes away. Also, if you actually limit vert.x to 1 CPU, it gets erratic and loses any performance benefits.