base/process/process_metrics.h - chromium/src - Git at Google

 // Copyright 2013 The Chromium Authors
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 // This file contains routines for gathering resource statistics for processes
 // running on the system.

 #ifndef BASE_PROCESS_PROCESS_METRICS_H_
 #define BASE_PROCESS_PROCESS_METRICS_H_

 #include <stddef.h>
 #include <stdint.h>

 #include <memory>

 #include "base/base_export.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/raw_ptr.h"
 #include "base/process/process_handle.h"
 #include "base/strings/string_piece.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "build/build_config.h"

 #if BUILDFLAG(IS_APPLE)
 #include <mach/mach.h>
 #include "base/process/port_provider_mac.h"

 #if !BUILDFLAG(IS_IOS)
 #include <mach/mach_vm.h>
 #endif
 #endif

 #if BUILDFLAG(IS_WIN)
 #include "base/win/scoped_handle.h"
 #include "base/win/windows_types.h"
 #endif

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
     BUILDFLAG(IS_AIX)
 #include <string>
 #include <utility>
 #include <vector>

 #include "base/threading/platform_thread.h"
 #endif

 namespace base {

 // Full declaration is in process_metrics_iocounters.h.
 struct IoCounters;

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
 // Minor and major page fault counts since the process creation.
 // Both counts are process-wide, and exclude child processes.
 //
 // minor: Number of page faults that didn't require disk IO.
 // major: Number of page faults that required disk IO.
 struct PageFaultCounts {
   int64_t minor;
   int64_t major;
 };
 #endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) ||
         // BUILDFLAG(IS_ANDROID)

 // Convert a POSIX timeval to microseconds.
 BASE_EXPORT int64_t TimeValToMicroseconds(const struct timeval& tv);

 // Provides performance metrics for a specified process (CPU usage and IO
 // counters). Use CreateCurrentProcessMetrics() to get an instance for the
 // current process, or CreateProcessMetrics() to get an instance for an
 // arbitrary process. Then, access the information with the different get
 // methods.
 //
 // This class exposes a few platform-specific APIs for parsing memory usage, but
 // these are not intended to generalize to other platforms, since the memory
 // models differ substantially.
 //
 // To obtain consistent memory metrics, use the memory_instrumentation service.
 //
 // For further documentation on memory, see
 // https://chromium.googlesource.com/chromium/src/+/HEAD/docs/README.md#Memory
 class BASE_EXPORT ProcessMetrics {
  public:
   ProcessMetrics(const ProcessMetrics&) = delete;
   ProcessMetrics& operator=(const ProcessMetrics&) = delete;

   ~ProcessMetrics();

   // Creates a ProcessMetrics for the specified process.
 #if !BUILDFLAG(IS_MAC)
   static std::unique_ptr<ProcessMetrics> CreateProcessMetrics(
       ProcessHandle process);
 #else

   // The port provider needs to outlive the ProcessMetrics object returned by
   // this function. If NULL is passed as provider, the returned object
   // only returns valid metrics if |process| is the current process.
   static std::unique_ptr<ProcessMetrics> CreateProcessMetrics(
       ProcessHandle process,
       PortProvider* port_provider);
 #endif  // !BUILDFLAG(IS_MAC)

   // Creates a ProcessMetrics for the current process. This a cross-platform
   // convenience wrapper for CreateProcessMetrics().
   static std::unique_ptr<ProcessMetrics> CreateCurrentProcessMetrics();

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
   // Resident Set Size is a Linux/Android specific memory concept. Do not
   // attempt to extend this to other platforms.
   BASE_EXPORT size_t GetResidentSetSize() const;
 #endif

   // Returns the percentage of time spent executing, across all threads of the
   // process, in the interval since the last time the method was called, using
   // the current |cumulative_cpu|. Since this considers the total execution time
   // across all threads in a process, the result can easily exceed 100% in
   // multi-thread processes running on multi-core systems. In general the result
   // is therefore a value in the range 0% to
   // SysInfo::NumberOfProcessors() * 100%.
   //
   // To obtain the percentage of total available CPU resources consumed by this
   // process over the interval, the caller must divide by NumberOfProcessors().
   //
   // Since this API measures usage over an interval, it will return zero on the
   // first call, and an actual value only on the second and subsequent calls.
   [[nodiscard]] double GetPlatformIndependentCPUUsage(TimeDelta cumulative_cpu);

   // Same as the above, but automatically calls GetCumulativeCPUUsage() to
   // determine the current cumulative CPU.
   [[nodiscard]] double GetPlatformIndependentCPUUsage();

   // Returns the cumulative CPU usage across all threads of the process since
   // process start. In case of multi-core processors, a process can consume CPU
   // at a rate higher than wall-clock time, e.g. two cores at full utilization
   // will result in a time delta of 2 seconds/per 1 wall-clock second.
   [[nodiscard]] TimeDelta GetCumulativeCPUUsage();

 #if BUILDFLAG(IS_WIN)
   // TODO(pmonette): Remove the precise version of the CPU usage functions once
   // we're validated that they are indeed better than the regular version above
   // and that they can replace the old implementation.

   // Returns the percentage of time spent executing, across all threads of the
   // process, in the interval since the last time the method was called, using
   // the current |cumulative_cpu|.
   //
   // Same as GetPlatformIndependentCPUUSage() but implemented using
   // `QueryProcessCycleTime` for higher precision.
   [[nodiscard]] double GetPreciseCPUUsage(TimeDelta cumulative_cpu);

   // Same as the above, but automatically calls GetPreciseCumulativeCPUUsage()
   // to determine the current cumulative CPU.
   [[nodiscard]] double GetPreciseCPUUsage();

   // Returns the cumulative CPU usage across all threads of the process since
   // process start. In case of multi-core processors, a process can consume CPU
   // at a rate higher than wall-clock time, e.g. two cores at full utilization
   // will result in a time delta of 2 seconds/per 1 wall-clock second.
   //
   // This is implemented using `QueryProcessCycleTime` for higher precision.
   [[nodiscard]] TimeDelta GetPreciseCumulativeCPUUsage();
 #endif  // BUILDFLAG(IS_WIN)

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
     BUILDFLAG(IS_AIX)
   // Emits the cumulative CPU usage for all currently active threads since they
   // were started into the output parameter (replacing its current contents).
   // Threads that have already terminated will not be reported. Thus, the sum of
   // these times may not equal the value returned by GetCumulativeCPUUsage().
   // Returns false on failure. We return the usage via an output parameter to
   // allow reuse of CPUUsagePerThread's std::vector by the caller, e.g. to avoid
   // allocations between repeated calls to this method.
   // NOTE: Currently only supported on Linux/Android.
   using CPUUsagePerThread = std::vector<std::pair<PlatformThreadId, TimeDelta>>;
   bool GetCumulativeCPUUsagePerThread(CPUUsagePerThread&);
 #endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) ||
         // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_AIX)

   // Returns the number of average idle cpu wakeups per second since the last
   // call.
   int GetIdleWakeupsPerSecond();

 #if BUILDFLAG(IS_APPLE)
   // Returns the number of average "package idle exits" per second, which have
   // a higher energy impact than a regular wakeup, since the last call.
   //
   // From the powermetrics man page:
   // "With the exception of some Mac Pro systems, Mac and
   // iOS systems are typically single package systems, wherein all CPUs are
   // part of a single processor complex (typically a single IC die) with shared
   // logic that can include (depending on system specifics) shared last level
   // caches, an integrated memory controller etc. When all CPUs in the package
   // are idle, the hardware can power-gate significant portions of the shared
   // logic in addition to each individual processor's logic, as well as take
   // measures such as placing DRAM in to self-refresh (also referred to as
   // auto-refresh), place interconnects into lower-power states etc"
   int GetPackageIdleWakeupsPerSecond();
 #endif

   // Retrieves accounting information for all I/O operations performed by the
   // process.
   // If IO information is retrieved successfully, the function returns true
   // and fills in the IO_COUNTERS passed in. The function returns false
   // otherwise.
   bool GetIOCounters(IoCounters* io_counters) const;

   // Returns the cumulative disk usage in bytes across all threads of the
   // process since process start.
   uint64_t GetCumulativeDiskUsageInBytes();

 #if BUILDFLAG(IS_POSIX)
   // Returns the number of file descriptors currently open by the process, or
   // -1 on error.
   int GetOpenFdCount() const;

   // Returns the soft limit of file descriptors that can be opened by the
   // process, or -1 on error.
   int GetOpenFdSoftLimit() const;
 #endif  // BUILDFLAG(IS_POSIX)

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
   // Bytes of swap as reported by /proc/[pid]/status.
   uint64_t GetVmSwapBytes() const;

   // Minor and major page fault count as reported by /proc/[pid]/stat.
   // Returns true for success.
   bool GetPageFaultCounts(PageFaultCounts* counts) const;
 #endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) ||
         // BUILDFLAG(IS_ANDROID)

   // Returns total memory usage of malloc.
   size_t GetMallocUsage();

  private:
 #if !BUILDFLAG(IS_MAC)
   explicit ProcessMetrics(ProcessHandle process);
 #else
   ProcessMetrics(ProcessHandle process, PortProvider* port_provider);
 #endif  // !BUILDFLAG(IS_MAC)

 #if BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX)
   int CalculateIdleWakeupsPerSecond(uint64_t absolute_idle_wakeups);
 #endif
 #if BUILDFLAG(IS_APPLE)
   // The subset of wakeups that cause a "package exit" can be tracked on macOS.
   // See |GetPackageIdleWakeupsForSecond| comment for more info.
   int CalculatePackageIdleWakeupsPerSecond(
       uint64_t absolute_package_idle_wakeups);

   // Queries the port provider if it's set.
   mach_port_t TaskForHandle(ProcessHandle process_handle) const;
 #endif

 #if BUILDFLAG(IS_WIN)
   win::ScopedHandle process_;
 #else
   ProcessHandle process_;
 #endif

   // Used to store the previous times and CPU usage counts so we can
   // compute the CPU usage between calls.
   TimeTicks last_cpu_time_;
 #if !BUILDFLAG(IS_FREEBSD) || !BUILDFLAG(IS_POSIX)
   TimeDelta last_cumulative_cpu_;
 #endif

 #if BUILDFLAG(IS_WIN)
   TimeTicks last_cpu_time_for_precise_cpu_usage_;
   TimeDelta last_precise_cumulative_cpu_;
 #endif

 #if BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX)
   // Same thing for idle wakeups.
   TimeTicks last_idle_wakeups_time_;
   uint64_t last_absolute_idle_wakeups_;
 #endif

 #if BUILDFLAG(IS_APPLE)
   // And same thing for package idle exit wakeups.
   TimeTicks last_package_idle_wakeups_time_;
   uint64_t last_absolute_package_idle_wakeups_;

   // Works around a race condition when combining two task_info() calls to
   // measure CPU time.
   TimeDelta last_measured_cpu_;
 #endif

 #if BUILDFLAG(IS_MAC)
   raw_ptr<PortProvider> port_provider_;
 #endif  // BUILDFLAG(IS_MAC)
 };

 // Returns the memory committed by the system in KBytes.
 // Returns 0 if it can't compute the commit charge.
 BASE_EXPORT size_t GetSystemCommitCharge();

 // Returns the maximum number of file descriptors that can be open by a process
 // at once. If the number is unavailable, a conservative best guess is returned.
 BASE_EXPORT size_t GetMaxFds();

 // Returns the maximum number of handles that can be open at once per process.
 BASE_EXPORT size_t GetHandleLimit();

 #if BUILDFLAG(IS_POSIX)
 // Increases the file descriptor soft limit to |max_descriptors| or the OS hard
 // limit, whichever is lower. If the limit is already higher than
 // |max_descriptors|, then nothing happens.
 BASE_EXPORT void IncreaseFdLimitTo(unsigned int max_descriptors);
 #endif  // BUILDFLAG(IS_POSIX)

 #if BUILDFLAG(IS_WIN) || BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) ||      \
     BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_AIX) || \
     BUILDFLAG(IS_FUCHSIA)
 // Data about system-wide memory consumption. Values are in KB. Available on
 // Windows, Mac, Linux, Android and Chrome OS.
 //
 // Total memory are available on all platforms that implement
 // GetSystemMemoryInfo(). Total/free swap memory are available on all platforms
 // except on Mac. Buffers/cached/active_anon/inactive_anon/active_file/
 // inactive_file/dirty/reclaimable/pswpin/pswpout/pgmajfault are available on
 // Linux/Android/Chrome OS. Shmem/slab are Chrome OS only.
 // Speculative/file_backed/purgeable are Mac and iOS only.
 // Free is absent on Windows (see "avail_phys" below).
 struct BASE_EXPORT SystemMemoryInfoKB {
   SystemMemoryInfoKB();
   SystemMemoryInfoKB(const SystemMemoryInfoKB& other);
   SystemMemoryInfoKB& operator=(const SystemMemoryInfoKB& other);

   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   int total = 0;

 #if !BUILDFLAG(IS_WIN)
   int free = 0;
 #endif

 #if BUILDFLAG(IS_WIN)
   // "This is the amount of physical memory that can be immediately reused
   // without having to write its contents to disk first. It is the sum of the
   // size of the standby, free, and zero lists." (MSDN).
   // Standby: not modified pages of physical ram (file-backed memory) that are
   // not actively being used.
   int avail_phys = 0;
 #endif

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
     BUILDFLAG(IS_AIX)
   // This provides an estimate of available memory as described here:
   // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773
   // NOTE: this is ONLY valid in kernels 3.14 and up.  Its value will always
   // be 0 in earlier kernel versions.
   // Note: it includes _all_ file-backed memory (active + inactive).
   int available = 0;
 #endif

 #if !BUILDFLAG(IS_APPLE)
   int swap_total = 0;
   int swap_free = 0;
 #endif

 #if BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || \
     BUILDFLAG(IS_AIX) || BUILDFLAG(IS_FUCHSIA)
   int buffers = 0;
   int cached = 0;
   int active_anon = 0;
   int inactive_anon = 0;
   int active_file = 0;
   int inactive_file = 0;
   int dirty = 0;
   int reclaimable = 0;
 #endif  // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_LINUX) ||
         // BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_AIX) BUILDFLAG(IS_FUCHSIA)

 #if BUILDFLAG(IS_CHROMEOS)
   int shmem = 0;
   int slab = 0;
 #endif  // BUILDFLAG(IS_CHROMEOS)

 #if BUILDFLAG(IS_APPLE)
   int speculative = 0;
   int file_backed = 0;
   int purgeable = 0;
 #endif  // BUILDFLAG(IS_APPLE)
 };

 // On Linux/Android/Chrome OS, system-wide memory consumption data is parsed
 // from /proc/meminfo and /proc/vmstat. On Windows/Mac, it is obtained using
 // system API calls.
 //
 // Fills in the provided |meminfo| structure. Returns true on success.
 // Exposed for memory debugging widget.
 BASE_EXPORT bool GetSystemMemoryInfo(SystemMemoryInfoKB* meminfo);

 #endif  // BUILDFLAG(IS_WIN) || BUILDFLAG(IS_APPLE) || BUILDFLAG(IS_LINUX) ||
         // BUILDFLAG(IS_CHROMEOS) BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_AIX) ||
         // BUILDFLAG(IS_FUCHSIA)

 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
     BUILDFLAG(IS_AIX)
 // Parse the data found in /proc/<pid>/stat and return the sum of the
 // CPU-related ticks.  Returns -1 on parse error.
 // Exposed for testing.
 BASE_EXPORT int ParseProcStatCPU(StringPiece input);

 // Get the number of threads of |process| as available in /proc/<pid>/stat.
 // This should be used with care as no synchronization with running threads is
 // done. This is mostly useful to guarantee being single-threaded.
 // Returns 0 on failure.
 BASE_EXPORT int64_t GetNumberOfThreads(ProcessHandle process);

 // /proc/self/exe refers to the current executable.
 BASE_EXPORT extern const char kProcSelfExe[];

 // Parses a string containing the contents of /proc/meminfo
 // returns true on success or false for a parsing error
 // Exposed for testing.
 BASE_EXPORT bool ParseProcMeminfo(StringPiece input,
                                   SystemMemoryInfoKB* meminfo);

 // Returns the memory committed by the system in KBytes, as from
 // GetSystemCommitCharge(), using data from `meminfo` instead of /proc/meminfo.
 // Exposed for testing.
 BASE_EXPORT size_t
 GetSystemCommitChargeFromMeminfo(const SystemMemoryInfoKB& meminfo);

 // Data from /proc/vmstat.
 struct BASE_EXPORT VmStatInfo {
   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   uint64_t pswpin = 0;
   uint64_t pswpout = 0;
   uint64_t pgmajfault = 0;
   uint64_t oom_kill = 0;
 };

 // Retrieves data from /proc/vmstat about system-wide vm operations.
 // Fills in the provided |vmstat| structure. Returns true on success.
 BASE_EXPORT bool GetVmStatInfo(VmStatInfo* vmstat);

 // Parses a string containing the contents of /proc/vmstat
 // returns true on success or false for a parsing error
 // Exposed for testing.
 BASE_EXPORT bool ParseProcVmstat(StringPiece input, VmStatInfo* vmstat);

 // Data from /proc/diskstats about system-wide disk I/O.
 struct BASE_EXPORT SystemDiskInfo {
   SystemDiskInfo();
   SystemDiskInfo(const SystemDiskInfo&);
   SystemDiskInfo& operator=(const SystemDiskInfo&);

   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   uint64_t reads = 0;
   uint64_t reads_merged = 0;
   uint64_t sectors_read = 0;
   uint64_t read_time = 0;
   uint64_t writes = 0;
   uint64_t writes_merged = 0;
   uint64_t sectors_written = 0;
   uint64_t write_time = 0;
   uint64_t io = 0;
   uint64_t io_time = 0;
   uint64_t weighted_io_time = 0;
 };

 // Checks whether the candidate string is a valid disk name, [hsv]d[a-z]+
 // for a generic disk or mmcblk[0-9]+ for the MMC case.
 // Names of disk partitions (e.g. sda1) are not valid.
 BASE_EXPORT bool IsValidDiskName(StringPiece candidate);

 // Retrieves data from /proc/diskstats about system-wide disk I/O.
 // Fills in the provided |diskinfo| structure. Returns true on success.
 BASE_EXPORT bool GetSystemDiskInfo(SystemDiskInfo* diskinfo);

 // Returns the amount of time spent in user space since boot across all CPUs.
 BASE_EXPORT TimeDelta GetUserCpuTimeSinceBoot();

 #endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) ||
         // BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_AIX)

 #if BUILDFLAG(IS_CHROMEOS)
 // Data from files in directory /sys/block/zram0 about ZRAM usage.
 struct BASE_EXPORT SwapInfo {
   SwapInfo()
       : num_reads(0),
         num_writes(0),
         compr_data_size(0),
         orig_data_size(0),
         mem_used_total(0) {
   }

   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   uint64_t num_reads = 0;
   uint64_t num_writes = 0;
   uint64_t compr_data_size = 0;
   uint64_t orig_data_size = 0;
   uint64_t mem_used_total = 0;
 };

 // Parses a string containing the contents of /sys/block/zram0/mm_stat.
 // This should be used for the new ZRAM sysfs interfaces.
 // Returns true on success or false for a parsing error.
 // Exposed for testing.
 BASE_EXPORT bool ParseZramMmStat(StringPiece mm_stat_data, SwapInfo* swap_info);

 // Parses a string containing the contents of /sys/block/zram0/stat
 // This should be used for the new ZRAM sysfs interfaces.
 // Returns true on success or false for a parsing error.
 // Exposed for testing.
 BASE_EXPORT bool ParseZramStat(StringPiece stat_data, SwapInfo* swap_info);

 // In ChromeOS, reads files from /sys/block/zram0 that contain ZRAM usage data.
 // Fills in the provided |swap_data| structure.
 // Returns true on success or false for a parsing error.
 BASE_EXPORT bool GetSwapInfo(SwapInfo* swap_info);

 // Data about GPU memory usage. These fields will be -1 if not supported.
 struct BASE_EXPORT GraphicsMemoryInfoKB {
   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   int gpu_objects = -1;
   int64_t gpu_memory_size = -1;
 };

 // Report on Chrome OS graphics memory. Returns true on success.
 // /run/debugfs_gpu is a bind mount into /sys/kernel/debug and synchronously
 // reading the in-memory files in /sys is fast in most cases. On platform that
 // reading the graphics memory info is slow, this function returns false.
 BASE_EXPORT bool GetGraphicsMemoryInfo(GraphicsMemoryInfoKB* gpu_meminfo);

 #endif  // BUILDFLAG(IS_CHROMEOS)

 struct BASE_EXPORT SystemPerformanceInfo {
   SystemPerformanceInfo();
   SystemPerformanceInfo(const SystemPerformanceInfo& other);
   SystemPerformanceInfo& operator=(const SystemPerformanceInfo& other);

   // Serializes the platform specific fields to value.
   Value::Dict ToDict() const;

   // Total idle time of all processes in the system (units of 100 ns).
   uint64_t idle_time = 0;
   // Number of bytes read.
   uint64_t read_transfer_count = 0;
   // Number of bytes written.
   uint64_t write_transfer_count = 0;
   // Number of bytes transferred (e.g. DeviceIoControlFile)
   uint64_t other_transfer_count = 0;
   // The amount of read operations.
   uint64_t read_operation_count = 0;
   // The amount of write operations.
   uint64_t write_operation_count = 0;
   // The amount of other operations.
   uint64_t other_operation_count = 0;
   // The number of pages written to the system's pagefiles.
   uint64_t pagefile_pages_written = 0;
   // The number of write operations performed on the system's pagefiles.
   uint64_t pagefile_pages_write_ios = 0;
   // The number of pages of physical memory available to processes running on
   // the system.
   uint64_t available_pages = 0;
   // The number of pages read from disk to resolve page faults.
   uint64_t pages_read = 0;
   // The number of read operations initiated to resolve page faults.
   uint64_t page_read_ios = 0;
 };

 // Retrieves performance counters from the operating system.
 // Fills in the provided |info| structure. Returns true on success.
 BASE_EXPORT bool GetSystemPerformanceInfo(SystemPerformanceInfo* info);

 // Collects and holds performance metrics for system memory and disk.
 // Provides functionality to retrieve the data on various platforms and
 // to serialize the stored data.
 class BASE_EXPORT SystemMetrics {
  public:
   SystemMetrics();

   static SystemMetrics Sample();

   // Serializes the system metrics to value.
   Value::Dict ToDict() const;

  private:
   FRIEND_TEST_ALL_PREFIXES(SystemMetricsTest, SystemMetrics);

   size_t committed_memory_;
 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
   SystemMemoryInfoKB memory_info_;
   VmStatInfo vmstat_info_;
   SystemDiskInfo disk_info_;
 #endif
 #if BUILDFLAG(IS_CHROMEOS)
   SwapInfo swap_info_;
   GraphicsMemoryInfoKB gpu_memory_info_;
 #endif
 #if BUILDFLAG(IS_WIN)
   SystemPerformanceInfo performance_;
 #endif
 };

 #if BUILDFLAG(IS_APPLE)
 enum class MachVMRegionResult {
   // There were no more memory regions between |address| and the end of the
   // virtual address space.
   Finished,

   // All output parameters are invalid.
   Error,

   // All output parameters are filled in.
   Success
 };

 // Returns info on the first memory region at or after |address|, including
 // protection values. On Success, |size| reflects the size of the
 // memory region.
 // Returns info on the first memory region at or after |address|, including
 // resident memory and share mode.
 // |size| and |info| are output parameters, only valid on Success.
 BASE_EXPORT MachVMRegionResult GetBasicInfo(mach_port_t task,
                                             mach_vm_size_t* size,
                                             mach_vm_address_t* address,
                                             vm_region_basic_info_64* info);

 // Returns info on the first memory region at or after |address|, including
 // resident memory and share mode. On Success, |size| reflects the size of the
 // memory region.
 // |size| and |info| are output parameters, only valid on Success.
 // |address| is an in-out parameter, than represents both the address to start
 // looking, and the start address of the memory region.
 BASE_EXPORT MachVMRegionResult GetTopInfo(mach_port_t task,
                                           mach_vm_size_t* size,
                                           mach_vm_address_t* address,
                                           vm_region_top_info_data_t* info);
 #endif  // BUILDFLAG(IS_APPLE)

 }  // namespace base

 #endif  // BASE_PROCESS_PROCESS_METRICS_H_