RFR: 8224817: Implementation of JEP 364: ZGC on macOS

[erik.osterlund at oracle.com]

Seems reasonable. Thanks.

/Erik

On 10/29/19 12:29 PM, Per Liden wrote:
> Some suggested adjustments, already discussed with Erik off-line:
>
> http://cr.openjdk.java.net/~pliden/8224817/webrev.review.0
>
> /Per
>
> On 10/28/19 5:11 PM, Erik Österlund wrote:
>> Hi,
>>
>> After some internal discussions with Per and Stefan, some 
>> refactorings have been made:
>>
>> 1) Use mmap consistently wherever possibly, instead of mach_vm_map, 
>> for consistency. And only use mach_vm_remap from a wrapper function 
>> to map in views.
>> 2) Move the pmem segments up one level so that producer and consumer 
>> of the segments is on the same level, and let the virtual "file" know 
>> only about offsets.
>> 3) Minor polishing.
>>
>> Incremental:
>> http://cr.openjdk.java.net/~eosterlund/8224817/webrev.00..01/
>>
>> Full:
>> http://cr.openjdk.java.net/~eosterlund/8224817/webrev.01/
>>
>> Thanks,
>> /Erik
>>
>> On 2019-10-24 12:38, erik.osterlund at oracle.com wrote:
>>> Hi,
>>>
>>> Now that some curling has been performed, paving way for this patch:
>>>
>>>     8229027: Improve how JNIHandleBlock::oops_do distinguishes oops 
>>> from non-oops
>>>     8229278: Improve hs_err location printing to assume less about 
>>> GC internals
>>>     8229189: Improve JFR leak profiler tracing to deal with 
>>> discontiguous heaps
>>>     8224815: Remove non-GC uses of CollectedHeap::is_in_reserved()
>>>     8224820: ZGC: Support discontiguous heap reservations
>>>
>>> ...the remaining thing to do is plugging in a few platform specific 
>>> ZGC files. This patch does that.
>>> Decided to go with mach_vm_map/mach_vm_remap to implement 
>>> multi-mapping. Previously I didn't want to do that as I couldn't 
>>> figure out how to mach_vm_remap memory on top of reserved VA 
>>> (acquired using mmap). But apparently VM_FLAGS_OVERWRITE was the 
>>> missing ingredient there. With that in place, dodging the terrible 
>>> ftruncate implementation on macOS seemed like a good idea. That also 
>>> implies this port supports large pages (unlike other GCs on macOS 
>>> today). Yay!
>>>
>>> CR:
>>> http://cr.openjdk.java.net/~eosterlund/8224817/webrev.00/
>>>
>>> Bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8229358
>>>
>>> Thanks,
>>> /Erik
>>