[aarch64-port-dev ] RFR: 8216557 Aarch64: Add support for Concurrent Class Unloading

[Stuart Monteith]

On 08/04/2020 17:15, Andrew Haley wrote:
> On 4/8/20 4:33 PM, Stuart Monteith wrote:
>> I see what you did there. This comes back to our previous discussion
>> about the value of having immediate oops at all. isn't that what you are
>> effectively suggesting? That would simply the code somewhat.
>
> No entirely. Immediate oops are good for most GCs. But according to what
> Erik said, immediate oops are verboten when we're using ZGC with concurrent
> method unloading, and it seems to be very easy to do.
>

I've incorporated everyone's comments into the latest:
        http://cr.openjdk.java.net/~smonteith/8216557/webrev.1/

I've cleaned up the logic somewhat - instead movoop will only make an
oop an immediate if there aren't nmethod entry guards - hopefully the
comments make than clear. This tested OK with a full run of JTREG.

I've made adding constants to wrapper only for AARCH64 with a comment
explaining why. I presume we don't want architectures that don't need it
to take the (albeit small) overhead. I've not made it conditional on
aarch64 with ZGC or class unloading.

BR,
        Stuart


IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.