diff --git a/compiler-rt/lib/profile/InstrProfilingFile.c b/compiler-rt/lib/profile/InstrProfilingFile.c
--- a/compiler-rt/lib/profile/InstrProfilingFile.c
+++ b/compiler-rt/lib/profile/InstrProfilingFile.c
@@ -490,6 +490,8 @@
    * __llvm_profile_get_size_for_buffer(). */
   const __llvm_profile_data *DataBegin = __llvm_profile_begin_data();
   const __llvm_profile_data *DataEnd = __llvm_profile_end_data();
+  const uint64_t *CountersBegin = __llvm_profile_begin_counters();
+  const uint64_t *CountersEnd = __llvm_profile_end_counters();
   uint64_t DataSize = __llvm_profile_get_data_size(DataBegin, DataEnd);
   const uint64_t CountersOffset = sizeof(__llvm_profile_header) +
       (DataSize * sizeof(__llvm_profile_data));
@@ -542,8 +544,18 @@
   }
 
   /* Update the profile fields based on the current mapping. */
-  __llvm_profile_counter_bias = (intptr_t)Profile -
-      (uintptr_t)__llvm_profile_begin_counters() + CountersOffset;
+  __llvm_profile_counter_bias =
+      (intptr_t)Profile - (uintptr_t)CountersBegin + CountersOffset;
+
+  /* Return the memory allocated for counters to OS. */
+  size_t PageSize = lprofGetPageSize();
+  uintptr_t CountersBeginAligned =
+      lprofRoundUpTo((uintptr_t)CountersBegin, PageSize);
+  uintptr_t CountersEndAligned =
+      lprofRoundDownTo((uintptr_t)CountersEnd, PageSize);
+  if (CountersBeginAligned < CountersEndAligned)
+    madvise((void *)CountersBeginAligned,
+            CountersEndAligned - CountersBeginAligned, MADV_DONTNEED);
 }
 
 static void initializeProfileForContinuousMode(void) {
diff --git a/compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c b/compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c
--- a/compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c
+++ b/compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c
@@ -192,9 +192,25 @@
   lprofWrite("LLVM Profile: {{{dumpfile:%s:%s}}}\n", ProfileSinkName, VmoName);
 
   /* Update the profile fields based on the current mapping. */
-  __llvm_profile_counter_bias = (intptr_t)Mapping -
-                                (uintptr_t)__llvm_profile_begin_counters() +
-                                CountersOffset;
+  __llvm_profile_counter_bias =
+      (intptr_t)Mapping - (uintptr_t)CountersBegin + CountersOffset;
+
+  /* Return the memory allocated for counters to OS. */
+  size_t PageSize = lprofGetPageSize();
+  zx_vaddr_t CountersBeginAligned =
+      lprofRoundUpTo((uintptr_t)CountersBegin, PageSize);
+  zx_vaddr_t CountersEndAligned =
+      lprofRoundDownTo((uintptr_t)CountersEnd, PageSize);
+  if (CountersBeginAligned < CountersEndAligned) {
+    Status = _zx_vmar_op_range(
+        _zx_vmar_root_self(), ZX_VMAR_OP_DECOMMIT, CountersBeginAligned,
+        CountersEndAligned - CountersBeginAligned, NULL, 0);
+    if (Status != ZX_OK) {
+      lprofWrite("LLVM Profile: cannot decommit counters: %s\n",
+                 _zx_status_get_string(Status));
+      return;
+    }
+  }
 }
 
 #endif
diff --git a/compiler-rt/lib/profile/InstrProfilingUtil.h b/compiler-rt/lib/profile/InstrProfilingUtil.h
--- a/compiler-rt/lib/profile/InstrProfilingUtil.h
+++ b/compiler-rt/lib/profile/InstrProfilingUtil.h
@@ -9,6 +9,7 @@
 #ifndef PROFILE_INSTRPROFILINGUTIL_H
 #define PROFILE_INSTRPROFILINGUTIL_H
 
+#include <inttypes.h>
 #include <stddef.h>
 #include <stdio.h>
 
@@ -73,4 +74,14 @@
 /* Restore previously suspended SIGKILL. */
 void lprofRestoreSigKill();
 
+size_t lprofGetPageSize();
+
+inline size_t lprofRoundUpTo(size_t x, size_t boundary) {
+  return (x + boundary - 1) & ~(boundary - 1);
+}
+
+inline size_t lprofRoundDownTo(size_t x, size_t boundary) {
+  return x & ~(boundary - 1);
+}
+
 #endif /* PROFILE_INSTRPROFILINGUTIL_H */
diff --git a/compiler-rt/lib/profile/InstrProfilingUtil.c b/compiler-rt/lib/profile/InstrProfilingUtil.c
--- a/compiler-rt/lib/profile/InstrProfilingUtil.c
+++ b/compiler-rt/lib/profile/InstrProfilingUtil.c
@@ -32,6 +32,10 @@
 #include <sys/prctl.h>
 #endif
 
+#if defined(__Fuchsia__)
+#include <zircon/syscalls.h>
+#endif
+
 #include "InstrProfiling.h"
 #include "InstrProfilingUtil.h"
 
@@ -330,3 +334,20 @@
   prctl(PR_SET_PDEATHSIG, SIGKILL);
 #endif
 }
+
+COMPILER_RT_VISIBILITY size_t lprofGetPageSize() {
+#if defined(__Fuchsia__)
+  return _zx_system_get_page_size();
+#elif defined(__APPLE__) || \
+      defined(__linux__) || \
+      defined(__FreeBSD__) || \
+      defined(__NetBSD__)
+  return sysconf(_SC_PAGESIZE);  // EXEC_PAGESIZE may not be trustworthy.
+#elif defined(_WIN32)
+  SYSTEM_INFO si;
+  GetSystemInfo(&si);
+  return si.dwPageSize;
+#else
+  return 4096;
+#endif
+}