IdleWakeups: enable filtering by process ID

This change makes IdleWakeups interpret a numeric target process as
a process ID. When a process ID is provided as the target, IdleWakeups
will track that process and its child processes.

This is useful for measuring a particular version of Chrome, e.g., a
local Chromium build, without needing to close all other running
versions.

Example usage:
idlewakeups.exe 22612

The above makes IdleWakeups take measurements for process ID 22612,
plus all of its child processes.

Change-Id: I267bfc1dda8f5c0600f3fc677e40ca0f6bb26f22
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490253
Commit-Queue: Jesse McKenna <jessemckenna@google.com>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819883}

tools/win/IdleWakeups/README.md

@@ -16,8 +16,11 @@ IdleWakeups.exe can then be found in src/tools/win/IdleWakeups/x64/Debug/.
 
 `IdleWakeups.exe msedge` to match all Edge processes.
 
+`IdleWakeups.exe 12345` to match process ID 12345 and its child processes.
+
 The process matching the provided parameter is identified by case-sensitive
-string prefix, e.g., `some_process` and `some_process.exe` would both work.
+string prefix, e.g., `some_process` and `some_process.exe` would both work. If
+the parameter is numeric and a valid process ID, it is treated as a process ID.
 
 When the tool starts it begins gathering and aggregating CPU usage, private
 working set size, number of context switches / sec, and power usage for all

tools/win/IdleWakeups/system_information_sampler.cpp

@@ -97,8 +97,8 @@ struct SYSTEM_PROCESS_INFORMATION {
   ULONGLONG KernelTime;
   UNICODE_STRING ImageName;
   KPRIORITY BasePriority;
-  HANDLE ProcessId;
-  HANDLE ParentProcessId;
+  HANDLE ProcessId;        // Actually process ID, not a handle
+  HANDLE ParentProcessId;  // Actually parent process ID, not a handle
   ULONG HandleCount;
   ULONG Reserved2[2];
   // Padding here in 64-bit
@@ -215,6 +215,14 @@ SystemInformationSampler::SystemInformationSampler(
   lstrcpyn(target_process_name_, process_name,
            sizeof(target_process_name_) / sizeof(wchar_t));
 
+  // If |target_process_name_| is numeric, treat it as a process ID.
+  errno = 0;
+  wchar_t* end_ptr;
+  target_process_id_ = wcstoul(target_process_name_, &end_ptr, 10);
+  // Discard result if error occurred, or if negative or only partially numeric.
+  if (errno != 0 || target_process_id_ < 0 || *end_ptr != L'\0')
+    target_process_id_ = 0;
+
   QueryPerformanceFrequency(&perf_frequency_);
   QueryPerformanceCounter(&initial_counter_);
 }
@@ -294,7 +302,16 @@ std::unique_ptr<ProcessDataSnapshot> SystemInformationSampler::TakeSnapshot() {
         break;
       }
 
-      if (pi->ImageName.Buffer) {
+      if (target_process_id_ > 0) {
+        // If |pi| or its parent has the targeted process ID, add its data to
+        // the snapshot.
+        if (reinterpret_cast<DWORD>(pi->ProcessId) == target_process_id_ ||
+            reinterpret_cast<DWORD>(pi->ParentProcessId) ==
+                target_process_id_) {
+          snapshot->processes.insert(
+              std::make_pair(pi->ProcessId, GetProcessData(pi)));
+        }
+      } else if (pi->ImageName.Buffer) {
         // Validate that the image name is within the buffer boundary.
         // ImageName.Length seems to be in bytes rather than characters.
         size_t image_name_offset =
@@ -302,7 +319,7 @@ std::unique_ptr<ProcessDataSnapshot> SystemInformationSampler::TakeSnapshot() {
         if (image_name_offset + pi->ImageName.Length > data_buffer.size())
           break;
 
-        // If |pi| is the targeted process, add its data to the snapshot.
+        // If |pi| has the targeted process name, add its data to the snapshot.
         if (wcsncmp(target_process_name_filter(), pi->ImageName.Buffer,
                     lstrlen(target_process_name_filter())) == 0) {
           snapshot->processes.insert(

tools/win/IdleWakeups/system_information_sampler.h

@@ -51,6 +51,10 @@ class SystemInformationSampler {
 
  private:
   wchar_t target_process_name_[256] = {};
+  // Process ID of target process. If nonzero, |target_process_name| is a
+  // process ID, so filter to this ID and its child processes.
+  DWORD target_process_id_ = 0;
+
   LARGE_INTEGER perf_frequency_;
   LARGE_INTEGER initial_counter_;
   size_t previous_buffer_size_ = 0;