Commit 492ceb9e authored by Doug Thayer's avatar Doug Thayer
Browse files

Bug 1538279 - Use CreateFileMapping with SEC_IMAGE to prefetch Windows DLLs r=aklotz 

Our old approach was reading this into a region of unexecutable memory,
meaning when we actually loaded the library it needed to be loaded into
executable memory. This fixes that. I suspect that any gains we were
seeing previously were due to hardware effects.

Differential Revision: https://phabricator.services.mozilla.com/D26018

--HG--
extra : moz-landing-system : lando
parent 2d3776cd

xpcom/glue/FileUtils.cpp

+35 −2
Original line number Diff line number Diff line
@@ -8,11 +8,13 @@ 


#include <errno.h>

#include <stdio.h>

#include <inttypes.h>



#include "nscore.h"

#include "private/pprio.h"

#include "prmem.h"

#include "mozilla/Assertions.h"

#include "mozilla/MemUtils.h"



#if defined(XP_MACOSX)

#  include <fcntl.h>
@@ -32,7 +34,8 @@ 
#  include <sys/types.h>

#  include <sys/stat.h>

#elif defined(XP_WIN)

#  include <windows.h>

#  include <nsWindowsHelpers.h>

#  include <mozilla/ScopeExit.h>

#endif



// Functions that are not to be used in standalone glue must be implemented
@@ -355,7 +358,37 @@ void mozilla::ReadAheadLib(mozilla::pathstr_t aFilePath) { 
    return;

  }

#if defined(XP_WIN)

  ReadAheadFile(aFilePath);

  nsAutoHandle fd(CreateFileW(aFilePath, GENERIC_READ,

                              FILE_SHARE_READ, nullptr, OPEN_EXISTING,

                              FILE_FLAG_SEQUENTIAL_SCAN, nullptr));

  if (!fd) {

    return;

  }

  LARGE_INTEGER fileSize = {};

  BOOL success = GetFileSizeEx(fd, &fileSize);

  if (!success || !fileSize.QuadPart ||

      fileSize.QuadPart > std::numeric_limits<size_t>::max()) {

    return;

  }



  nsAutoHandle mapping(CreateFileMapping(fd, nullptr,

                                         SEC_IMAGE | PAGE_READONLY,

                                         0, 0, nullptr));



  if (!mapping) {

    return;

  }



  PVOID data = MapViewOfFile(mapping, FILE_MAP_READ, 0, 0, (size_t)fileSize.QuadPart);

  auto guard = MakeScopeExit([=]() { UnmapViewOfFile(data); });



  if (data && !MaybePrefetchMemory((uint8_t*)data, (size_t)fileSize.QuadPart)) {

    volatile uint8_t read = 0;

    for(size_t i = 0; i < (size_t)fileSize.QuadPart; i += 4096) {

      read += ((uint8_t*)data)[i];

    }

  }



#elif defined(LINUX) && !defined(ANDROID)

  int fd = open(aFilePath, O_RDONLY);

  if (fd < 0) {

xpcom/glue/standalone/moz.build

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 


SOURCES += [

    '../FileUtils.cpp',

    '../MemUtils.cpp',

    'nsXPCOMGlue.cpp',

]