xpcom/glue/MemUtils.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/MemUtils.h"
   8
   9 #if defined(XP_WIN)
  10 #  include <windows.h>
  11 #  include "mozilla/Maybe.h"
  12 #else
  13 #  include <sys/mman.h>
  14 #endif
  15
  16 #if defined(XP_WIN)
  17 typedef BOOL(WINAPI* PrefetchVirtualMemoryFn)(HANDLE, ULONG_PTR, PVOID, ULONG);
  18
  19 static mozilla::Maybe<PrefetchVirtualMemoryFn> sPrefetchVirtualMemory;
  20
  21 void MaybeInitPrefetchVirtualMemory() {
  22   if (sPrefetchVirtualMemory.isNothing()) {
  23     sPrefetchVirtualMemory.emplace(
  24         reinterpret_cast<PrefetchVirtualMemoryFn>(GetProcAddress(
  25             GetModuleHandleW(L"kernel32.dll"), "PrefetchVirtualMemory")));
  26   }
  27 }
  28 #endif
  29
  30 bool mozilla::CanPrefetchMemory() {
  31 #if defined(XP_SOLARIS) || defined(XP_UNIX)
  32   return true;
  33 #elif defined(XP_WIN)
  34   MaybeInitPrefetchVirtualMemory();
  35   return *sPrefetchVirtualMemory;
  36 #else
  37   return false;
  38 #endif
  39 }
  40
  41 void mozilla::PrefetchMemory(uint8_t* aStart, size_t aNumBytes) {
  42   if (aNumBytes == 0) {
  43     return;
  44   }
  45
  46 #if defined(XP_SOLARIS)
  47   posix_madvise(aStart, aNumBytes, POSIX_MADV_WILLNEED);
  48 #elif defined(XP_UNIX)
  49   madvise(aStart, aNumBytes, MADV_WILLNEED);
  50 #elif defined(XP_WIN)
  51   MaybeInitPrefetchVirtualMemory();
  52   if (*sPrefetchVirtualMemory) {
  53     // Normally, we'd use WIN32_MEMORY_RANGE_ENTRY, but that requires
  54     // a different _WIN32_WINNT value before including windows.h, but
  55     // that causes complications with unified sources. It's a simple
  56     // enough struct anyways.
  57     struct {
  58       PVOID VirtualAddress;
  59       SIZE_T NumberOfBytes;
  60     } entry;
  61     entry.VirtualAddress = aStart;
  62     entry.NumberOfBytes = aNumBytes;
  63     (*sPrefetchVirtualMemory)(GetCurrentProcess(), 1, &entry, 0);
  64     return;
  65   }
  66 #endif
  67 }