diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
index 5c5b6f7ebe58d..a50c394d2146e 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
@@ -105,7 +105,7 @@ class ShenandoahPretouchHeapTask : public WorkerTask {
     ShenandoahHeapRegion* r = _regions.next();
     while (r != nullptr) {
       if (r->is_committed()) {
-        os::pretouch_memory(r->bottom(), r->end(), _page_size);
+        os::pretouch_memory_unsafe(r->bottom(), r->end(), _page_size);
       }
       r = _regions.next();
     }
@@ -133,7 +133,7 @@ class ShenandoahPretouchBitmapTask : public WorkerTask {
       assert (end <= _bitmap_size, "end is sane: " SIZE_FORMAT " < " SIZE_FORMAT, end, _bitmap_size);
 
       if (r->is_committed()) {
-        os::pretouch_memory(_bitmap_base + start, _bitmap_base + end, _page_size);
+        os::pretouch_memory_unsafe(_bitmap_base + start, _bitmap_base + end, _page_size);
       }
 
       r = _regions.next();
@@ -2352,7 +2352,7 @@ bool ShenandoahHeap::commit_bitmap_slice(ShenandoahHeapRegion* r) {
   }
 
   if (AlwaysPreTouch) {
-    os::pretouch_memory(start, start + len, _pretouch_bitmap_page_size);
+    os::pretouch_memory_unsafe(start, start + len, _pretouch_bitmap_page_size);
   }
 
   return true;
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
index 8a94b20670a9f..faa942fe73a01 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
@@ -627,7 +627,7 @@ void ShenandoahHeapRegion::do_commit() {
     report_java_out_of_memory("Unable to commit bitmaps for region");
   }
   if (AlwaysPreTouch) {
-    os::pretouch_memory(bottom(), end(), heap->pretouch_heap_page_size());
+    os::pretouch_memory_unsafe(bottom(), end(), heap->pretouch_heap_page_size());
   }
   heap->increase_committed(ShenandoahHeapRegion::region_size_bytes());
 }
diff --git a/src/hotspot/share/runtime/os.cpp b/src/hotspot/share/runtime/os.cpp
index 6cb57e9dcb6e5..217e6120dc396 100644
--- a/src/hotspot/share/runtime/os.cpp
+++ b/src/hotspot/share/runtime/os.cpp
@@ -2228,6 +2228,21 @@ void os::pretouch_memory(void* start, void* end, size_t page_size) {
   }
 }
 
+void os::pretouch_memory_unsafe(void* start, void* end, size_t page_size) {
+  assert(start <= end, "invalid range: " PTR_FORMAT " -> " PTR_FORMAT, p2i(start), p2i(end));
+  assert(is_power_of_2(page_size), "page size misaligned: %zu", page_size);
+  assert(page_size >= sizeof(int), "page size too small: %zu", page_size);
+  if (start < end) {
+    // This is not a concurrent safe pretouch, so we have to stay within the range.
+    const size_t pd_page_size = pd_pretouch_memory(start, end, page_size);
+    if (pd_page_size > 0) {
+      for (volatile char *p = (char*)start; p < (char*)end; p += page_size) {
+        *p = 0;
+      }
+    }
+  }
+}
+
 char* os::map_memory_to_file(size_t bytes, int file_desc, MEMFLAGS flag) {
   // Could have called pd_reserve_memory() followed by replace_existing_mapping_with_file_mapping(),
   // but AIX may use SHM in which case its more trouble to detach the segment and remap memory to the file.
diff --git a/src/hotspot/share/runtime/os.hpp b/src/hotspot/share/runtime/os.hpp
index 63ea172166729..b26609356a414 100644
--- a/src/hotspot/share/runtime/os.hpp
+++ b/src/hotspot/share/runtime/os.hpp
@@ -495,6 +495,11 @@ class os: AllStatic {
   // Other threads may use the memory range concurrently with pretouch.
   static void   pretouch_memory(void* start, void* end, size_t page_size = vm_page_size());
 
+  // Same as pretouch_memory, but unsafe: writes into the pretouched memory,
+  // and so could only be used when callers are sure the memory does not carry
+  // anything useful.
+  static void   pretouch_memory_unsafe(void* start, void* end, size_t page_size = vm_page_size());
+
   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
                                bool is_committed = true);