RFC: Make Traversal GC default in dev?

[Roman Kennke]

Am 23.05.2018 um 11:40 schrieb 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.

So how about including it in backports, after Roland got the C2 enqueue
barriers in shape? That should make it easier to give it some more
exposure to early testers, and also make your backporting life easier?

Roman