RFR: 8237198+8237199+8237200: ZGC: Share heap multi-mapping code across platforms

[erik.osterlund at oracle.com]

Hi Per,

I like the red stuff. +1

/Erik

On 1/15/20 1:57 PM, Per Liden wrote:
> Hi,
>
> Please review this cleanup of the ZPhysicalMemory/ZBackingFile layer, 
> which aims to de-duplicate some of the multi-mapping code. I've split 
> the change into three separate patches, the main patch followed by two 
> patches doing some renaming.
>
>
> 1) The ZBackingFile code was designed to allow platforms to decide if 
> they want to use heap multi-mapping or some other (possibly HW 
> supported) scheme. As of today, all our supported platforms do heap 
> multi-mapping, so there's some degree of code duplication in 
> ZBackingFile for each platform. This patch moves common multi-mapping 
> code into ZPhysicalMemoryManager. If we in the future find that we 
> want to support a platform that doesn't do multi-mapping, then we can 
> introduce an abstraction for this again.
> Bug: https://bugs.openjdk.java.net/browse/JDK-8237198
> Webrev: http://cr.openjdk.java.net/~pliden/8237198/webrev.0
>
>
> 2) Rename ZBackingFile to ZPhysicalMemoryBacking, since "File" is 
> somewhat misleading on platforms other than Linux.
> Bug: https://bugs.openjdk.java.net/browse/JDK-8237199
> Webrev: http://cr.openjdk.java.net/~pliden/8237199/webrev.0
>
>
> 3) Rename ZBackingPath to ZMountPoint, as it's a better name in light 
> of JDK-8237199.
> Bug: https://bugs.openjdk.java.net/browse/JDK-8237200
> Webrev: http://cr.openjdk.java.net/~pliden/8237200/webrev.0
>
>
> cheers,
> Per