Introducing JetStream 2.1

JetStream 2 is a JavaScript benchmark suite that runs 64 subtests. We recently discovered that the benchmark score of JetStream 2 may be influenced by pause times between individual subtests because of second order effects, like CPU ramping. Network latency is one source of such pause times. As a result, depending on the speed of one’s network, JetStream 2’s benchmark score can vary. This is undesirable since the goal of JetStream 2 is to measure JavaScript performance, not the second order effects of network latency.

We’re introducing JetStream 2.1 which runs the same subtests as JetStream 2. However, JetStream 2.1 updates the benchmark driver to pre-fetch network resources into Blobs, and create URLs from them. The subtests will now load resources from these blob URLs instead.

With this change, we measured JetStream 2.1’s benchmark scores on both Chrome and Safari to be more stable and is less perturbed by pause times due to network latency. Scores produced from JetStream 2.1 are not comparable to other versions of any JetStream benchmark.