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

Stuart Monteith stumon01 at arm.com
Thu Apr 16 11:29:19 UTC 2020

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:

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.


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