[profile] Decommit memory after counter relocation

After we relocate counters, we no longer need to keep the original copy
around so we can return the memory back to the operating system.

Differential Revision: https://reviews.llvm.org/D104839

compiler-rt/lib/profile/InstrProfilingFile.c

@@ -490,6 +490,8 @@ static void relocateCounters(void) {
    * __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 +544,11 @@ static void relocateCounters(void) {
   }
 
   /* 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. */
+  lprofReleaseMemoryPagesToOS((uintptr_t)CountersBegin, (uintptr_t)CountersEnd);
 }
 
 static void initializeProfileForContinuousMode(void) {

compiler-rt/lib/profile/InstrProfilingPlatformFuchsia.c

@@ -192,9 +192,11 @@ void __llvm_profile_initialize(void) {
   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. */
+  lprofReleaseMemoryPagesToOS((uintptr_t)CountersBegin, (uintptr_t)CountersEnd);
 }
 
 #endif

compiler-rt/lib/profile/InstrProfilingUtil.c

@@ -12,12 +12,13 @@
 #include <windows.h>
 #include "WindowsMMap.h"
 #else
+#include <errno.h>
+#include <fcntl.h>
 #include <sys/file.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
-#include <fcntl.h>
-#include <errno.h>
 #endif
 
 #ifdef COMPILER_RT_HAS_UNAME
@@ -32,6 +33,10 @@
 #include <sys/prctl.h>
 #endif
 
+#if defined(__Fuchsia__)
+#include <zircon/syscalls.h>
+#endif
+
 #include "InstrProfiling.h"
 #include "InstrProfilingUtil.h"
 
@@ -330,3 +335,21 @@ COMPILER_RT_VISIBILITY void lprofRestoreSigKill() {
   prctl(PR_SET_PDEATHSIG, SIGKILL);
 #endif
 }
+
+COMPILER_RT_VISIBILITY int lprofReleaseMemoryPagesToOS(uintptr_t Begin,
+                                                       uintptr_t End) {
+  size_t PageSize = getpagesize();
+  uintptr_t BeginAligned = lprofRoundUpTo((uintptr_t)Begin, PageSize);
+  uintptr_t EndAligned = lprofRoundDownTo((uintptr_t)End, PageSize);
+  if (BeginAligned < EndAligned) {
+#if defined(__Fuchsia__)
+    return _zx_vmar_op_range(_zx_vmar_root_self(), ZX_VMAR_OP_DECOMMIT,
+                             (zx_vaddr_t)BeginAligned,
+                             EndAligned - BeginAligned, NULL, 0);
+#else
+    return madvise((void *)BeginAligned, EndAligned - BeginAligned,
+                   MADV_DONTNEED);
+#endif
+  }
+  return 0;
+}

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 @@ int lprofSuspendSigKill();
 /* Restore previously suspended SIGKILL. */
 void lprofRestoreSigKill();
 
+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);
+}
+
+int lprofReleaseMemoryPagesToOS(uintptr_t Begin, uintptr_t End);
+
 #endif /* PROFILE_INSTRPROFILINGUTIL_H */

compiler-rt/lib/profile/WindowsMMap.c

@@ -112,6 +112,18 @@ int msync(void *addr, size_t length, int flags)
   return 0;
 }
 
+COMPILER_RT_VISIBILITY
+int madvise(void *addr, size_t length, int advice)
+{
+  if (advice != MADV_DONTNEED)
+    return -1; /* Not supported. */
+
+  if (!VirtualUnlock(addr, length))
+    return -1;
+
+  return 0;
+}
+
 COMPILER_RT_VISIBILITY
 int lock(HANDLE handle, DWORD lockType, BOOL blocking) {
   DWORD flags = lockType;

compiler-rt/lib/profile/WindowsMMap.h

@@ -36,6 +36,14 @@
 #define MS_INVALIDATE   0x0002  /* invalidate all cached data */
 #define MS_SYNC         0x0010  /* msync synchronously */
 
+/*
+ * madvise() flags
+ */
+
+#define MADV_NORMAL     0   /* no special treatment */
+#define MADV_WILLNEED   3   /* expect access in the near future */
+#define MADV_DONTNEED   4   /* do not expect access in the near future */
+
 /*
  * flock() operations
  */
@@ -59,6 +67,8 @@ void munmap(void *addr, size_t length);
 
 int msync(void *addr, size_t length, int flags);
 
+int madvise(void *addr, size_t length, int advice);
+
 int flock(int fd, int operation);
 
 #endif /* _WIN32 */