Shenandoah Degenerated GC long pause 1

gc.log

Trigger: Free (5631M) is below minimum threshold (5632M)
Free: 5631M (460 regions), Max regular: 16384K, Max humongous: 425984K, External frag: 93%, Internal frag: 23%
Evacuation Reserve: 2816M (176 regions), Max regular: 16384K
2019-01-08T16:47:04.358+0000: 340115.832: [Concurrent resetUsing 25 of 25 workers for concurrent reset
Failed to allocate 2048K
Cancelling GC: Allocation Failure
 46G->52G(55G), 11069.097 ms]
2019-01-08T16:47:15.433+0000: 340126.907: [Pause Init Mark (process weakrefs)Using 25 of 25 workers for init marking
Pacer for Mark. Expected Live: 1917M, Free: 0M, Non-Taxable: 0M, Alloc Tax Rate: infx
, 4.328 ms]
2019-01-08T16:47:15.437+0000: 340126.911: [Concurrent marking (process weakrefs)Using 25 of 25 workers for concurrent marking
 52G->52G(55G), 6.329 ms]
Free: 0M (0 regions), Max regular: 0K, Max humongous: 0K, External frag: 0%, Internal frag: 0%
Evacuation Reserve: 2816M (176 regions), Max regular: 16384K
Pacer for Idle. Initial: 1126M, Alloc Tax Rate: 1.0x
Trigger: Handle Allocation Failure
Free: 0M (0 regions), Max regular: 0K, Max humongous: 0K, External frag: 0%, Internal frag: 0%
Evacuation Reserve: 2816M (176 regions), Max regular: 16384K
2019-01-08T16:47:15.449+0000: 340126.923: [Pause Degenerated GC (Mark)Using 25 of 25 workers for stw degenerated gc
Adaptive CSet Selection. Target Free: 5632M, Actual Free: 2864M, Max CSet: 2346M, Min Garbage: 2768M
Collectable Garbage: 50937M (99% of total), 1644M CSet, 3297 CSet regions
Immediate Garbage: 48M (0% of total), 3 regions
Pacer for Evacuation. Used CSet: 52582M, Free: 48M, Non-Taxable: 4M, Alloc Tax Rate: 2644.4x
Pacer for Update Refs. Used: 54960M, Free: 48M, Non-Taxable: 4M, Alloc Tax Rate: 1382.0x
Used: before: 53334M, after: 2377M
Internal frag: before: 0.3%, after: 0.2%
External frag: before: 75.4%, after: 14.8%
 52G->2377M(55G), 310.040 ms]
Free: 51124M (3197 regions), Max regular: 16384K, Max humongous: 47071232K, External frag: 11%, Internal frag: 0%
Evacuation Reserve: 2816M (176 regions), Max regular: 16384K
Pacer for Idle. Initial: 1126M, Alloc Tax Rate: 1.0x