Task manager: Get physical memory efficiently for all processes from SharedSampler

chrome/browser/win/private_working_set_snapshot.h

-// Copyright 2015 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.
-
-#ifndef CHROME_BROWSER_WIN_PRIVATE_WORKING_SET_SNAPSHOT_H_
-#define CHROME_BROWSER_WIN_PRIVATE_WORKING_SET_SNAPSHOT_H_
-
-#include "build/build_config.h"
-
-#include <pdh.h>
-#include <stddef.h>
-
-#include <vector>
-
-#include "base/macros.h"
-#include "base/process/process_handle.h"
-#include "base/win/scoped_handle.h"
-
-namespace win {
-
-// The traits class for PDH handles that can be closed via PdhCloseQuery() API.
-struct PDHHandleTraits {
-  typedef PDH_HQUERY Handle;
-  static PDH_HQUERY NullHandle() { return nullptr; }
-  static bool IsHandleValid(PDH_HQUERY handle) { return handle != nullptr; }
-  static bool CloseHandle(PDH_HQUERY handle) {
-    return (PdhCloseQuery(handle) == ERROR_SUCCESS);
-  }
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(PDHHandleTraits);
-};
-
-// DummyVerifierTraits can be used because PDH_HQUERY is just a typedef for
-// HANDLE. However HandleTraits cannot be used because PdhCloseQuery must be
-// called rather than CloseHandle to dispose of the resources.
-using ScopedPDH =
-    base::win::GenericScopedHandle<PDHHandleTraits,
-                                   base::win::DummyVerifierTraits>;
-
-}  // namespace win
-
-// This class can be used to do bulk collection of private working sets. This
-// exists because on Windows it is much faster to collect a group of private
-// working sets all at once using PdhOpenQuery than to calculate the private
-// working sets for each process individually.
-class PrivateWorkingSetSnapshot {
- public:
-  PrivateWorkingSetSnapshot();
-  ~PrivateWorkingSetSnapshot();
-
-  // Add a process name that this object should monitor, such as "chrome". All
-  // processes whose name starts with this string will be monitored.
-  void AddToMonitorList(const std::string& process_name);
-
-  // Query the system for working-set information for all monitored processes
-  // and update the results cache. This function may take a few ms to run.
-  // The time it takes seems to be independent of the number of processes it
-  // retrieves data for. This makes it faster than using QueryWorkingSet as soon
-  // as the process count exceeds two or three.
-  void Sample();
-
-  // Ask for the working set for a specific process, from the most recent call
-  // to Sample. If no data is available then zero will be returned. The result
-  // is in bytes.
-  size_t GetPrivateWorkingSet(base::ProcessId process_id) const;
-
- private:
-  // Initialize the PDH |query_handle_| and process any pending AddToMonitorList
-  // calls.
-  void Initialize();
-
-  // This holds a pair of Pdh counters to queries for the process ID and private
-  // working set for a particular process name being monitored. The results from
-  // the two queries can be matched up so that we can associate a private
-  // working set with a process ID.
-  struct PdhCounterPair {
-    // These are bound to query_handle_ and will be freed when it is closed.
-    // The handle to the 'counter' that retrieves process IDs.
-    PDH_HCOUNTER process_id_handle = nullptr;
-    // The handle to the 'counter' that retrieves private working sets.
-    PDH_HCOUNTER private_ws_handle = nullptr;
-  };
-
-  // Struct for storing a process ID and associated private working set.
-  struct PidAndPrivateWorkingSet {
-    base::ProcessId process_id;
-    size_t private_ws;
-    // Comparison function for sorting by process ID.
-    bool operator<(const PidAndPrivateWorkingSet& other) const {
-      // private_ws is intentionally *not* part of the comparison because it is
-      // the payload and process_id is the key.
-      return process_id < other.process_id;
-    }
-    // Comparison function for searching by process ID.
-    bool operator<(const base::ProcessId other_process_id) const {
-      return process_id < other_process_id;
-    }
-  };
-
-  // True if Initialize() has been called, whether it succeeded or not.
-  bool initialized_ = false;
-
-  // The handle to the query object.
-  win::ScopedPDH query_handle_;
-
-  // A vector of process names to monitor when initialization occurs.
-  std::vector<std::string> process_names_;
-
-  // A PdhCounterPair for each successful AddToMonitorList call.
-  std::vector<PdhCounterPair> counter_pairs_;
-
-  // After each call to Sample this will hold the results, sorted by process id.
-  std::vector<PidAndPrivateWorkingSet> records_;
-
-  DISALLOW_COPY_AND_ASSIGN(PrivateWorkingSetSnapshot);
-};
-
-#endif  // CHROME_BROWSER_WIN_PRIVATE_WORKING_SET_SNAPSHOT_H_