Introduction

A number of people describe Valhalla recently as being "primarily about performance".  While it is understandable why people might come to that conclusion -- many of the motivations for Valhalla are, in fact, rooted in performance considerations -- this characterization misses something very important.  Yes, performance is an important part of the story -- but so are safety, abstraction, encapsulation, expressiveness, maintainability, and compatible library evolution.

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Just providing these features for new libraries is not enough; if widely used libraries can't compatibly evolve to take advantage of this new world, they are effectively consigned to a slow death. This might be OK for some classes -- deprecating OldX and replacing it with NewX -- but only when uses of the OldX types aren't strewn through lots of other libraries.  That rules out starting fresh with Collections, Streams, JSR-310, and many other abstractions, without rewriting the whole JDK (and many third party libraries).  So instead, we have to provide a compatible path for such libraries (and their clients) to modernize.

Summary

So, to summarize: Valhalla may be motivated by performance considerations, but a better way to view it as enhancing abstraction, encapsulation, safety, expressiveness, and maintainability -- without giving up performance.