Of course, as with whenever you change something fundamental like this, some programs will get slower while others get faster. That's the nature of trade offs.

Of course, as with whenever you change something fundamental like this, some programs will get slower while others get faster. That's the nature of trade offs. It's not really suspect. The benchmarks reflect execution speed. The new GC trades a little raw throughput for lower GC latency. So you would expect a GC-heavy benchmark to show the greatest speed loss. What matters for go users, though, is the behaviour of real programs. Real programs benefit from the reduced latency of the GC and other compiler optimisations we have made since 1.4. The outcome, in our measurements, is roughly equivalent performance for most programs but with significantly shorter GC pauses.