Add UMA stats for hard-fault counts for Windows 7 and greater.

components/startup_metric_utils/startup_metric_utils.cc

Index: components/startup_metric_utils/startup_metric_utils.cc
diff --git a/components/startup_metric_utils/startup_metric_utils.cc b/components/startup_metric_utils/startup_metric_utils.cc
index 642a0c488823b675c2468a2098e0277227823212..b82da00fd0ccae419bfde47b2b76766cc6995ec9 100644
--- a/components/startup_metric_utils/startup_metric_utils.cc
+++ b/components/startup_metric_utils/startup_metric_utils.cc
@@ -16,6 +16,11 @@
 #include "base/sys_info.h"
 #include "base/time/time.h"
 
+#if defined(OS_WIN)
+#include <winternl.h>
+#include "base/win/windows_version.h"
+#endif
+
 namespace {
 
 // Mark as volatile to defensively make sure usage is thread-safe.
@@ -40,6 +45,151 @@ base::Lock* GetSubsystemStartupTimeHashLock() {
   return slow_startup_time_hash_lock;
 }
 
+#if defined(OS_WIN)
+
+// The struct used to return system process information via the NT internal
+// QuerySystemInformation call. This is partially documented at
+// http://goo.gl/Ja9MrH and fully documented at http://goo.gl/QJ70rn
+// This structure is laid out in the same format on both 32-bit and 64-bit
+// systems, but has a different size due to the various pointer-sized fields.
+struct SYSTEM_PROCESS_INFORMATION_EX {
+  ULONG NextEntryOffset;
+  ULONG NumberOfThreads;
+  LARGE_INTEGER WorkingSetPrivateSize;
+  ULONG HardFaultCount;
+  BYTE Reserved1[36];
+  PVOID Reserved2[3];
+  // This is labeled a handle so that it expands to the correct size for 32-bit
+  // and 64-bit operating systems. However, under the hood it's a 32-bit DWORD
+  // containing the process ID.
+  HANDLE UniqueProcessId;
+  PVOID Reserved3;
+  ULONG HandleCount;
+  BYTE Reserved4[4];
+  PVOID Reserved5[11];
+  SIZE_T PeakPagefileUsage;
+  SIZE_T PrivatePageCount;
+  LARGE_INTEGER Reserved6[6];
+  // Array of SYSTEM_THREAD_INFORMATION structs follows.
+};
+
+// The signature of the NtQuerySystemInformation function.
+typedef NTSTATUS (WINAPI *NtQuerySystemInformationPtr)(
+    SYSTEM_INFORMATION_CLASS, PVOID, ULONG, PULONG);
+
+// Gets the hard fault count of the current process, returning it via
+// |hard_fault_count|. Returns true on success, false otherwise. Also returns
+// whether or not the system call was even possible for the current OS version
+// via |has_os_support|.
+bool GetHardFaultCountForCurrentProcess(uint32_t* hard_fault_count,
+                                        bool* has_os_support) {
+  DCHECK(hard_fault_count);
+  DCHECK(has_os_support);
+
+  if (base::win::GetVersion() < base::win::VERSION_WIN7) {
+    *has_os_support = false;
+    return false;
+  }
+  // At this point the OS supports the required system call.
+  *has_os_support = true;
+
+  // Get the function pointer.
+  NtQuerySystemInformationPtr query_sys_info =
+      reinterpret_cast<NtQuerySystemInformationPtr>(
+          ::GetProcAddress(GetModuleHandle(L"ntdll.dll"),
+                           "NtQuerySystemInformation"));
+  if (query_sys_info == nullptr)
+    return false;
+
+  // The output of this system call depends on the number of threads and
+  // processes on the entire system, and this can change between calls. Retry
+  // a small handful of times growing the buffer along the way.
+  // NOTE: The actual required size depends entirely on the number of processes
+  //       and threads running on the system. The initial guess suffices for
+  //       ~100s of processes and ~1000s of threads.
+  std::vector<uint8_t> buffer(32 * 1024);
+  for (size_t tries = 0; tries < 3; ++tries) {
+    ULONG return_length = 0;
+    NTSTATUS status = query_sys_info(
+        SystemProcessInformation,
+        buffer.data(),
+        static_cast<ULONG>(buffer.size()),
+        &return_length);
+    // Insufficient space in the buffer.
+    if (return_length > buffer.size()) {
+      buffer.resize(return_length);
+      continue;
+    }
+    if (NT_SUCCESS(status) && return_length <= buffer.size())
+      break;
+    return false;
+  }
+
+  // Look for the struct housing information for the current process.
+  DWORD proc_id = ::GetCurrentProcessId();
+  size_t index = 0;
+  while (index < buffer.size()) {
+    DCHECK_LE(index + sizeof(SYSTEM_PROCESS_INFORMATION_EX), buffer.size());
+    SYSTEM_PROCESS_INFORMATION_EX* proc_info =
+        reinterpret_cast<SYSTEM_PROCESS_INFORMATION_EX*>(buffer.data() + index);
+    if (reinterpret_cast<DWORD>(proc_info->UniqueProcessId) == proc_id) {
+      *hard_fault_count = proc_info->HardFaultCount;
+      return true;
+    }
+    // The list ends when NextEntryOffset is zero. This also prevents busy
+    // looping if the data is in fact invalid.
+    if (proc_info->NextEntryOffset <= 0)
+      return false;
+    index += proc_info->NextEntryOffset;
+  }
+
+  return false;
+}
+
+#endif  // defined(OS_WIN)
+
+// On Windows, records the number of hard-faults that have occurred in the
+// current chrome.exe process since it was started. This is a nop on other
+// platforms.
+// crbug.com/476923
+// TODO(chrisha): If this proves useful, use it to split startup stats in two.
+void RecordHardFaultHistogram(bool is_first_run) {
+#if defined(OS_WIN)
+  uint32_t hard_fault_count = 0;
+  bool has_os_support = false;
+  bool success = GetHardFaultCountForCurrentProcess(
+      &hard_fault_count, &has_os_support);
+
+  // Log whether or not the system call was successful, assuming the OS was
+  // detected to support it.
+  if (has_os_support) {
+    UMA_HISTOGRAM_BOOLEAN(
+        "Startup.BrowserMessageLoopStartHardFaultCount.Success",
+        success);
+  }
+
+  // Don't log a histogram value if unable to get the hard fault count.
+  if (!success)
+    return;
+
+  // Hard fault counts are expected to be in the thousands range,
+  // corresponding to faulting in ~10s of MBs of code ~10s of KBs at a time.
+  // (Observed to vary from 1000 to 10000 on various test machines and
+  // platforms.)
+  if (is_first_run) {
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Startup.BrowserMessageLoopStartHardFaultCount.FirstRun",
+        hard_fault_count,
+        0, 40000, 50);
+  } else {
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Startup.BrowserMessageLoopStartHardFaultCount",
+        hard_fault_count,
+        0, 40000, 50);
+  }
+#endif  // defined(OS_WIN)
+}
+
 // Record time of main entry so it can be read from Telemetry performance
 // tests.
 // TODO(jeremy): Remove once crbug.com/317481 is fixed.
@@ -115,6 +265,7 @@ const base::Time MainEntryStartTime() {
 }
 
 void OnBrowserStartupComplete(bool is_first_run) {
+  RecordHardFaultHistogram(is_first_run);
   RecordMainEntryTimeHistogram();
 
   // Bail if uptime < 7 minutes, to filter out cases where Chrome may have been