RFR: 8245203/8245204/8245208: ZGC: Don't hold the ZPageAllocator lock while committing/uncommitting memory

[Stefan Karlsson]

On 2020-05-18 23:23, Per Liden wrote:
> Please review this series of three patches to rework the page 
> allocation path so that we don't hold the ZPageAllocator lock while 
> committing/uncommitting memory. Patch 1 & 2 are small and preparatory. 
> Patch 3 is the main patch and it's unfortunately fairly large as it 
> was hard to break up in a sensible way.
>
> ---------------------
>
> 1) 8245203: ZGC: Don't track size in ZPhysicalMemoryBacking
>
> To make it easier to allow for more concurrent commit/uncommit we 
> should not track the backing "size" in ZPhysicalMemoryBacking. Instead 
> we can add the full physical memory range (from 0 to max_capacity) to 
> the list of uncommitted memory at startup. This removes the need to 
> track and update the backing size (which otherwise needs to be 
> properly synchronized).
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8245203
> Webrev: http://cr.openjdk.java.net/~pliden/8245203/webrev.0

Most of this looks good. You removed the EINTR while loop from the 
ftruncate call. Is that not needed anymore?

Thanks,
StefanK