Experimental pre-reading optimization to run on perf bots...

chrome/app/client_util.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <windows.h>
 #include <shlwapi.h>
 
 #include "chrome/app/breakpad_win.h"
 #include "chrome/app/client_util.h"
 #include "chrome/common/chrome_switches.h"
@@ skipping 63 matching lines @@
 bool EnvQueryStr(const wchar_t* key_name, std::wstring* value) {
   wchar_t out[128];
   DWORD count = sizeof(out)/sizeof(out[0]);
   DWORD rv = ::GetEnvironmentVariableW(key_name, out, count);
   if ((rv == 0) || (rv >= count))
     return false;
   *value = out;
   return true;
 }
 
+bool IsRunningHeadless() {
+  return (0 != ::GetEnvironmentVariableW(L"CHROME_HEADLESS", NULL, 0));
+}
+
 // Expects that |dir| has a trailing backslash. |dir| is modified so it
 // contains the full path that was tried. Caller must check for the return
 // value not being null to dermine if this path contains a valid dll.
 HMODULE LoadChromeWithDirectory(std::wstring* dir) {
   ::SetCurrentDirectoryW(dir->c_str());
 #ifdef _WIN64
   const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
   if ((cmd_line.GetSwitchValueASCII(switches::kProcessType) ==
       switches::kNaClBrokerProcess) ||
       (cmd_line.GetSwitchValueASCII(switches::kProcessType) ==
       switches::kNaClLoaderProcess)) {
     // Load the 64-bit DLL when running in a 64-bit process.
     dir->append(installer_util::kChromeNaCl64Dll);
   } else {
     // Only NaCl broker and loader can be launched as Win64 processes.
     NOTREACHED();
     return NULL;
   }
 #else
   dir->append(installer_util::kChromeDll);
 #endif
+
+  // Experimental pre-reading optimization
+  // The idea is to pre read significant portion of chrome.dll in advance
+  // so that subsequent hard page faults are avoided.
+  DWORD pre_read_size_mb = 0;
+  const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
+  if (!cmd_line.HasSwitch(switches::kProcessType) &&
+      (IsRunningHeadless() || InstallUtil::IsChromeFrameProcess())) {
+    HKEY key = NULL;
+    if (::RegOpenKeyEx(HKEY_CURRENT_USER, L"Software\\Google\\ChromeFrame",
+                       0, KEY_QUERY_VALUE, &key) == ERROR_SUCCESS) {
+      DWORD unused = sizeof(pre_read_size_mb);
+      RegQueryValueEx(key, L"PreRead", NULL, NULL,
+                      reinterpret_cast<LPBYTE>(&pre_read_size_mb), &unused);
+      RegCloseKey(key);
+      key = NULL;
+    } else {
+      pre_read_size_mb = 16; // Read in first 16 MB by default.
+    }
+  }
+
+  if (pre_read_size_mb) {
+    HANDLE chrome_dll = CreateFile(dir->c_str(),
+                                       GENERIC_READ,
+                                       FILE_SHARE_READ | FILE_SHARE_WRITE,
+                                       NULL,
+                                       OPEN_EXISTING,
+                                       FILE_FLAG_SEQUENTIAL_SCAN,
+                                       NULL);
+    if (chrome_dll == INVALID_HANDLE_VALUE) {
+      DWORD error = GetLastError();
+      DLOG(ERROR) << __FUNCTION__ << " CreateFile( "
+          << dir->c_str() << " ) failed. Error: " << error;
+    } else {
+      const size_t kChunkSize = 1024 * 1024; // 1 MB
+      void* buffer = VirtualAlloc(NULL, kChunkSize, MEM_COMMIT, PAGE_READWRITE);
+      if (buffer) {
+        size_t read_size = pre_read_size_mb * kChunkSize;
+        DWORD read = 0;
+        while (::ReadFile(chrome_dll, buffer, kChunkSize, &read, NULL)) {
+          // nothing to do here...
+          read_size -= std::min(size_t(read), read_size);
+          if (!read || !read_size)
+            break;
+        }
+
+        VirtualFree(buffer, 0, MEM_RELEASE);
+      }
+
+      CloseHandle(chrome_dll);
+    }
+  }
+
   return ::LoadLibraryExW(dir->c_str(), NULL,
                           LOAD_WITH_ALTERED_SEARCH_PATH);
 }
 
 // Set did_run "dr" in omaha's client state for this product.
 bool SetDidRunState(const wchar_t* guid, const wchar_t* value) {
   std::wstring key_path(google_update::kRegPathClientState);
   key_path.append(L"\\").append(guid);
   HKEY reg_key;
   if (::RegCreateKeyExW(HKEY_CURRENT_USER, key_path.c_str(), 0, NULL,
@@ skipping 137 matching lines @@
   }
 };
 
 MainDllLoader* MakeMainDllLoader() {
 #if defined(GOOGLE_CHROME_BUILD)
   return new ChromeDllLoader();
 #else
   return new ChromiumDllLoader();
 #endif
 }