Port CoreCLR#13736 fix to CoreRT (#4627)

1 files changed, 40 insertions, 14 deletions

diff --git a/src/Native/gc/gc.cpp b/src/Native/gc/gc.cpp
index e95ac1f93..1800d84bc 100644
--- a/src/Native/gc/gc.cpp
+++ b/src/Native/gc/gc.cpp
@@ -15752,40 +15752,66 @@ start_no_gc_region_status gc_heap::prepare_for_no_gc_region (uint64_t total_size
     save_data_for_no_gc();
     settings.pause_mode = pause_no_gc;
     current_no_gc_region_info.start_status = start_no_gc_success;
-    
-    size_t allocation_no_gc_loh = 0;
-    size_t allocation_no_gc_soh = 0;
-    size_t size_per_heap = 0;
 
-    total_size = (size_t)((float)total_size * 1.05);
+    uint64_t allocation_no_gc_loh = 0;
+    uint64_t allocation_no_gc_soh = 0;
+    assert(total_size != 0);
     if (loh_size_known)
     {
-        loh_size = (size_t)((float)loh_size * 1.05);
-        allocation_no_gc_loh = (size_t)loh_size;
-        allocation_no_gc_soh = (size_t)(total_size - loh_size);
+        assert(loh_size != 0);
+        assert(loh_size <= total_size);
+        allocation_no_gc_loh = loh_size;
+        allocation_no_gc_soh = total_size - loh_size;
     }
     else
     {
-        allocation_no_gc_soh = (size_t)total_size;
-        allocation_no_gc_loh = (size_t)total_size;
+        allocation_no_gc_soh = total_size;
+        allocation_no_gc_loh = total_size;
     }
 
     size_t soh_segment_size = get_valid_segment_size();
     int soh_align_const = get_alignment_constant (TRUE);
-    size_t max_soh_allocated = (soh_segment_size - OS_PAGE_SIZE - eph_gen_starts_size);
+    size_t max_soh_allocated = soh_segment_size - OS_PAGE_SIZE - eph_gen_starts_size;
+    size_t size_per_heap = 0;
+    const double scale_factor = 1.05;
 
     int num_heaps = 1;
 #ifdef MULTIPLE_HEAPS
     num_heaps = n_heaps;
-#endif //MULTIPLE_HEAPS
-    size_t total_allowed_soh_allocation = max_soh_allocated * num_heaps;
+#endif // MULTIPLE_HEAPS
 
-    if (allocation_no_gc_soh > total_allowed_soh_allocation)
+    uint64_t total_allowed_soh_allocation = max_soh_allocated * num_heaps;
+    // [LOCALGC TODO]
+    // In theory, the upper limit here is the physical memory of the machine, not
+    // SIZE_T_MAX. This is not true today because total_physical_mem can be
+    // larger than SIZE_T_MAX if running in wow64 on a machine with more than
+    // 4GB of RAM. Once Local GC code divergence is resolved and code is flowing
+    // more freely between branches, it would be good to clean this up to use
+    // total_physical_mem instead of SIZE_T_MAX.
+    assert(total_allowed_soh_allocation <= SIZE_T_MAX);
+    uint64_t total_allowed_loh_allocation = SIZE_T_MAX;
+    uint64_t total_allowed_soh_alloc_scaled = allocation_no_gc_soh > 0 ? static_cast<uint64_t>(total_allowed_soh_allocation / scale_factor) : 0;
+    uint64_t total_allowed_loh_alloc_scaled = allocation_no_gc_loh > 0 ? static_cast<uint64_t>(total_allowed_loh_allocation / scale_factor) : 0;
+
+    if (allocation_no_gc_soh > total_allowed_soh_alloc_scaled ||
+        allocation_no_gc_loh > total_allowed_loh_alloc_scaled)
     {
         status = start_no_gc_too_large;
         goto done;
     }
 
+    if (allocation_no_gc_soh > 0)
+    {
+        allocation_no_gc_soh = static_cast<uint64_t>(allocation_no_gc_soh * scale_factor);
+        allocation_no_gc_soh = min (allocation_no_gc_soh, total_allowed_soh_alloc_scaled);
+    }
+
+    if (allocation_no_gc_loh > 0)
+    {
+        allocation_no_gc_loh = static_cast<uint64_t>(allocation_no_gc_loh * scale_factor);
+        allocation_no_gc_loh = min (allocation_no_gc_loh, total_allowed_loh_alloc_scaled);
+    }
+
     if (disallow_full_blocking)
         current_no_gc_region_info.minimal_gc_p = TRUE;