1 files changed, 67 insertions, 0 deletions
diff --git a/xpcom/glue/MemUtils.cpp b/xpcom/glue/MemUtils.cpp
new file mode 100644
index 0000000000..531a5ea2f5
--- /dev/null
+++ b/xpcom/glue/MemUtils.cpp
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/MemUtils.h"
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#  include "mozilla/Maybe.h"
+#else
+#  include <sys/mman.h>
+#endif
+
+#if defined(XP_WIN)
+typedef BOOL(WINAPI* PrefetchVirtualMemoryFn)(HANDLE, ULONG_PTR, PVOID, ULONG);
+
+static mozilla::Maybe<PrefetchVirtualMemoryFn> sPrefetchVirtualMemory;
+
+void MaybeInitPrefetchVirtualMemory() {
+  if (sPrefetchVirtualMemory.isNothing()) {
+    sPrefetchVirtualMemory.emplace(
+        reinterpret_cast<PrefetchVirtualMemoryFn>(GetProcAddress(
+            GetModuleHandleW(L"kernel32.dll"), "PrefetchVirtualMemory")));
+  }
+}
+#endif
+
+bool mozilla::CanPrefetchMemory() {
+#if defined(XP_SOLARIS) || defined(XP_UNIX)
+  return true;
+#elif defined(XP_WIN)
+  MaybeInitPrefetchVirtualMemory();
+  return *sPrefetchVirtualMemory;
+#else
+  return false;
+#endif
+}
+
+void mozilla::PrefetchMemory(uint8_t* aStart, size_t aNumBytes) {
+  if (aNumBytes == 0) {
+    return;
+  }
+
+#if defined(XP_SOLARIS)
+  posix_madvise(aStart, aNumBytes, POSIX_MADV_WILLNEED);
+#elif defined(XP_UNIX)
+  madvise(aStart, aNumBytes, MADV_WILLNEED);
+#elif defined(XP_WIN)
+  MaybeInitPrefetchVirtualMemory();
+  if (*sPrefetchVirtualMemory) {
+    // Normally, we'd use WIN32_MEMORY_RANGE_ENTRY, but that requires
+    // a different _WIN32_WINNT value before including windows.h, but
+    // that causes complications with unified sources. It's a simple
+    // enough struct anyways.
+    struct {
+      PVOID VirtualAddress;
+      SIZE_T NumberOfBytes;
+    } entry;
+    entry.VirtualAddress = aStart;
+    entry.NumberOfBytes = aNumBytes;
+    (*sPrefetchVirtualMemory)(GetCurrentProcess(), 1, &entry, 0);
+    return;
+  }
+#endif
+}