RFR (S): 8131319: Move G1Allocator::_summary_bytes_used back to G1CollectedHeap

Mikael Gerdin mikael.gerdin at oracle.com
Tue Jul 21 12:57:24 UTC 2015


Hi Thomas,

On 2015-07-15 12:47, Thomas Schatzl wrote:
> Hi all,
>
>    can I have comments and reviews for the following change to move
> G1Allocator::_summary_bytes_used to a more fitting place?
>
> The problem from my POV is, that the member
> G1Allocator::_summary_bytes_used, that contains the number of bytes held
> by the heap outside of the allocators is located within G1Allocator.
>
> That sounds odd, particularly because G1Allocator actually never uses
> it, it's managed completely by G1CollectedHeap.
>
> Before the addition of the G1ArchiveAllocator one could have made the
> argument that G1Allocator holds all memory contained in the heap, but
> this is not true any more: the memory occupied by G1ArchiveAllocator
> needs to be added to the total sum of all managed space anyway, so
> moving _summary_bytes_used out of G1Allocator seems sensible (to me).
>
> I talked to StefanJ about this change who originally moved
> _summary_used_bytes into G1Allocator, and we could not find an argument
> for keeping _summary_used_bytes in G1Allocator.
>
> This allows us to also refine the responsibilities of G1Allocator a
> little more, to be the owner of the current allocation areas (regions)
> only.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8131319
>
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8131319/webrev/

The change looks good to me.
Have you double-checked that the agent changes work (with jmap -heap)?

/Mikael

>
> Testing:
> jprt
>
> Thanks,
>    Thomas
>
>


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