RFR: mmap connection matrix

[Roman Kennke]

Am 22.05.2017 um 12:19 schrieb Aleksey Shipilev:
> On 05/22/2017 12:11 PM, Roman Kennke wrote:
>> Am 22.05.2017 um 11:41 schrieb Aleksey Shipilev:
>>> Hi,
>>>
>>> Currently the connection matrix is allocated in C heap. We can make it
>>> consistent with marking bitmaps by mmap-ing the matrix as well:
>>>  http://cr.openjdk.java.net/~shade/shenandoah/matrix-mmap/webrev.01/
>>>
>>> Testing: hotspot_gc_shenandoah
>>>
>>> -Aleksey
>>>
>> It seems ugly that the allocation of the matrix is outside the
>> ConnectionMatrix class. ShenandoahHeap now needs knowledge about
>> internals of ConnectionMatrix.
> There is already a fair amount of cohesion between ShMatrix and ShHeap. This
> change makes ShMatrix the "view" over naked bitmap allocated in ShHeap.
>
> Consider the upside: matrix can now be allocated with proper page sizes and
> alignment.

Why not put that part here:

+ ReservedSpace matrix_bitmap(_max_regions * _max_regions, page_size);
+ os::commit_memory_or_exit(matrix_bitmap.base(), matrix_bitmap.size(),
false,
+ "couldn't allocate matrix bitmap");
+ MemTracker::record_virtual_memory_type(matrix_bitmap.base(), mtGC);


inside ConnectionMatrix constructor?

Roman