RFC: Make Traversal GC default in dev?

[Aleksey Shipilev]

On 05/23/2018 11:04 AM, Roman Kennke wrote:
> What speaks against making Traversal GC the default mode in dev branch? It seems to equal or
> exceed performance and latency in most cases, sometimes dramatically, it provides better
> footprint properties due to incremental-updatish algorithm, a simpler barrier story, etc. Early
> testers have uncovered some bugs, but now seem happy with it. What's holding it back? 

From the top of my head:

1) Throughput is not necessarily better: Compiler.* is ~4% slower, Derby is ~2% slower

2) There is no traversal in sh/jdk9 and sh/jdk8, and most of our adopters are on sh/jdk8, so not
only this move would split our adopter user base, depending on what version they are running, but it
also provides us no substantial exposure benefits.

3) Recent C2 barrier work have not been ported/verified for traversal?

I believe traversal is the future going forward, but there are also engineering things we need to
complete before we consider it to be default.

-Aleksey

P.S. Aren't you on vacation?