SWDEV-482851 - Do not release last suballocator chunk

Change-Id: Ib28dc9df68e454ee0c0c699c1ff17588fd55f802


[ROCm/clr commit: 451b0ce768]

projects/clr/rocclr/device/pal/palresource.cpp

@@ -2207,7 +2207,8 @@ bool MemorySubAllocator::Free(amd::Monitor* monitor, GpuMemoryReference* ref, Pa
 
     it->second->Free(offset);
     // If this suballocator empty, then release memory chunk
-    if (it->second->IsEmpty()) {
+    // while keeping at least one chunk available, if retain_final_chunk is true
+    if (it->second->IsEmpty() && !(retain_final_chunk_ && heaps_.size() == 1)) {
       delete it->second;
       heaps_.erase(it);
       release_mem = true;

projects/clr/rocclr/device/pal/palresource.hpp

@@ -535,7 +535,8 @@ typedef Util::BuddyAllocator<Device> MemBuddyAllocator;
 
 class MemorySubAllocator : public amd::HeapObject {
  public:
-  MemorySubAllocator(Device* device) : device_(device) {}
+  MemorySubAllocator(Device* device, bool retain_final_chunk = false)
+      : device_(device), retain_final_chunk_(retain_final_chunk) {}
 
   ~MemorySubAllocator();
 
@@ -553,6 +554,7 @@ class MemorySubAllocator : public amd::HeapObject {
 
   Device* device_;
   std::unordered_map<GpuMemoryReference*, MemBuddyAllocator*> heaps_;
+  bool retain_final_chunk_;
 };
 
 class CoarseMemorySubAllocator : public MemorySubAllocator {
@@ -564,7 +566,8 @@ class CoarseMemorySubAllocator : public MemorySubAllocator {
 
 class FineMemorySubAllocator : public MemorySubAllocator {
  public:
-  FineMemorySubAllocator(Device* device) : MemorySubAllocator(device) {}
+  FineMemorySubAllocator(Device* device)
+      : MemorySubAllocator(device, true /*retain_final_chunk*/) {}
 
   bool CreateChunk(const Pal::IGpuMemory* reserved_va) override;
 };