Implement iotop

iotop provides per process statistics on IO rates and kernel delays.
Requires root, and a kernel compiled with CONFIG_TASKSTATS,
CONFIG_TASK_DELAY_ACCT, and CONFIG_TASK_IO_ACCOUNTING.

Change-Id: I111c55a1492e9ea33d8d7b3ab620080625b84346

7 files changed, 698 insertions, 0 deletions

diff --git a/iotop/Android.mk b/iotop/Android.mk
new file mode 100644
index 00000000..b8a146df
--- /dev/null
+++ b/iotop/Android.mk
@@ -0,0 +1,28 @@
+# Copyright (C) 2015 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+LOCAL_PATH:= $(call my-dir)
+include $(CLEAR_VARS)
+
+LOCAL_SRC_FILES := iotop.cpp tasklist.cpp taskstats.cpp
+
+LOCAL_MODULE := iotop
+
+LOCAL_MODULE_TAGS := debug
+
+LOCAL_SHARED_LIBRARIES := libnl libbase
+
+LOCAL_CFLAGS := -Wall -Werror
+
+include $(BUILD_EXECUTABLE)
diff --git a/iotop/MODULE_LICENSE_APACHE2 b/iotop/MODULE_LICENSE_APACHE2
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/iotop/MODULE_LICENSE_APACHE2
diff --git a/iotop/iotop.cpp b/iotop/iotop.cpp
new file mode 100644
index 00000000..e2d7e0b8
--- /dev/null
+++ b/iotop/iotop.cpp
@@ -0,0 +1,253 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <getopt.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <algorithm>
+#include <map>
+#include <unordered_map>
+#include <vector>
+
+#include <base/logging.h>
+
+#include "tasklist.h"
+#include "taskstats.h"
+
+constexpr uint64_t NSEC_PER_SEC = 1000000000;
+
+static uint64_t BytesToKB(uint64_t bytes) {
+  return (bytes + 1024-1) / 1024;
+}
+
+static float TimeToTgidPercent(uint64_t ns, int time, const TaskStatistics& stats) {
+  float percent = ns / stats.threads() / (time * NSEC_PER_SEC / 100.0f);
+  return std::min(percent, 99.99f);
+}
+
+static void usage(char* myname) {
+  printf(
+      "Usage: %s [-h] [-P] [-d <delay>] [-n <cycles>] [-s <column>]\n"
+      "   -d  Set the delay between refreshes in seconds.\n"
+      "   -h  Display this help screen.\n"
+      "   -m  Set the number of processes or threads to show\n"
+      "   -n  Set the number of refreshes before exiting.\n"
+      "   -P  Show processes instead of the default threads.\n"
+      "   -s  Set the column to sort by:\n"
+      "       pid, read, write, total, io, swap, sched, mem or delay.\n",
+      myname);
+}
+
+using Sorter = std::function<void(std::vector<TaskStatistics>&)>;
+static Sorter GetSorter(const std::string field) {
+  // Generic comparator
+  static auto comparator = [](auto& lhs, auto& rhs, auto field, bool ascending) -> bool {
+    auto a = (lhs.*field)();
+    auto b = (rhs.*field)();
+    if (a != b) {
+      // Sort by selected field
+      return ascending ^ (a < b);
+    } else {
+      // And then fall back to sorting by pid
+      return lhs.pid() < rhs.pid();
+    }
+  };
+
+  auto make_sorter = [](auto field, bool ascending) {
+    // Make closure for comparator on a specific field
+    using namespace std::placeholders;
+    auto bound_comparator = std::bind(comparator, _1, _2, field, ascending);
+
+    // Return closure to std::sort with specialized comparator
+    return [bound_comparator](auto& vector) {
+      return std::sort(vector.begin(), vector.end(), bound_comparator);
+    };
+  };
+
+  static const std::map<std::string, Sorter> sorters{
+      {"pid", make_sorter(&TaskStatistics::pid, false)},
+      {"read", make_sorter(&TaskStatistics::read, true)},
+      {"write", make_sorter(&TaskStatistics::write, true)},
+      {"total", make_sorter(&TaskStatistics::read_write, true)},
+      {"io", make_sorter(&TaskStatistics::delay_io, true)},
+      {"swap", make_sorter(&TaskStatistics::delay_swap, true)},
+      {"sched", make_sorter(&TaskStatistics::delay_sched, true)},
+      {"mem", make_sorter(&TaskStatistics::delay_mem, true)},
+      {"delay", make_sorter(&TaskStatistics::delay_total, true)},
+  };
+
+  auto it = sorters.find(field);
+  if (it == sorters.end()) {
+    return nullptr;
+  }
+  return it->second;
+}
+
+int main(int argc, char* argv[]) {
+  bool processes = false;
+  int delay = 1;
+  int cycles = -1;
+  int limit = -1;
+  Sorter sorter = GetSorter("total");
+
+  android::base::InitLogging(argv, android::base::StderrLogger);
+
+  while (1) {
+    int c;
+    static const option longopts[] = {
+        {"delay", required_argument, 0, 'd'},
+        {"help", 0, 0, 'h'},
+        {"limit", required_argument, 0, 'm'},
+        {"iter", required_argument, 0, 'n'},
+        {"sort", required_argument, 0, 's'},
+        {"processes", 0, 0, 'P'},
+        {0, 0, 0, 0},
+    };
+    c = getopt_long(argc, argv, "d:hm:n:Ps:", longopts, NULL);
+    if (c < 0) {
+      break;
+    }
+    switch (c) {
+    case 'd':
+      delay = atoi(optarg);
+      break;
+    case 'h':
+      usage(argv[0]);
+      return(EXIT_SUCCESS);
+    case 'm':
+      limit = atoi(optarg);
+      break;
+    case 'n':
+      cycles = atoi(optarg);
+      break;
+    case 's': {
+      sorter = GetSorter(optarg);
+      if (sorter == nullptr) {
+        LOG(ERROR) << "Invalid sort column \"" << optarg << "\"";
+        usage(argv[0]);
+        return(EXIT_FAILURE);
+      }
+      break;
+    }
+    case 'P':
+      processes = true;
+      break;
+    case '?':
+      usage(argv[0]);
+      return(EXIT_FAILURE);
+    default:
+      abort();
+    }
+  }
+
+  std::map<pid_t, std::vector<pid_t>> tgid_map;
+
+  TaskstatsSocket taskstats_socket;
+  taskstats_socket.Open();
+
+  std::unordered_map<pid_t, TaskStatistics> pid_stats;
+  std::unordered_map<pid_t, TaskStatistics> tgid_stats;
+  std::vector<TaskStatistics> stats;
+
+  bool first = true;
+  bool second = true;
+
+  while (true) {
+    stats.clear();
+    if (!TaskList::Scan(tgid_map)) {
+      LOG(FATAL) << "failed to scan tasks";
+    }
+    for (auto& tgid_it : tgid_map) {
+      pid_t tgid = tgid_it.first;
+      std::vector<pid_t>& pid_list = tgid_it.second;
+
+      TaskStatistics tgid_stats_new;
+      TaskStatistics tgid_stats_delta;
+
+      if (processes) {
+        // If printing processes, collect stats for the tgid which will
+        // hold delay accounting data across all threads, including
+        // ones that have exited.
+        if (!taskstats_socket.GetTgidStats(tgid, tgid_stats_new)) {
+          continue;
+        }
+        tgid_stats_delta = tgid_stats[tgid].Update(tgid_stats_new);
+      }
+
+      // Collect per-thread stats
+      for (pid_t pid : pid_list) {
+        TaskStatistics pid_stats_new;
+        if (!taskstats_socket.GetPidStats(pid, pid_stats_new)) {
+          continue;
+        }
+
+        TaskStatistics pid_stats_delta = pid_stats[pid].Update(pid_stats_new);
+
+        if (processes) {
+          tgid_stats_delta.AddPidToTgid(pid_stats_delta);
+        } else {
+          stats.push_back(pid_stats_delta);
+        }
+      }
+
+      if (processes) {
+        stats.push_back(tgid_stats_delta);
+      }
+    }
+
+    if (!first) {
+      sorter(stats);
+      if (!second) {
+        printf("\n");
+      }
+      printf("%6s %-16s %20s %34s\n", "", "",
+          "--- IO (KiB/s) ---", "----------- delayed on ----------");
+      printf("%6s %-16s %6s %6s %6s  %-5s  %-5s  %-5s  %-5s  %-5s\n",
+          "PID",
+          "Command",
+          "read",
+          "write",
+          "total",
+          "IO",
+          "swap",
+          "sched",
+          "mem",
+          "total");
+      int n = limit;
+      for (const TaskStatistics& statistics : stats) {
+        printf("%6d %-16s %6" PRIu64 " %6" PRIu64 " %6" PRIu64 " %5.2f%% %5.2f%% %5.2f%% %5.2f%% %5.2f%%\n",
+            statistics.pid(),
+            statistics.comm().c_str(),
+            BytesToKB(statistics.read()),
+            BytesToKB(statistics.write()),
+            BytesToKB(statistics.read_write()),
+            TimeToTgidPercent(statistics.delay_io(), delay, statistics),
+            TimeToTgidPercent(statistics.delay_swap(), delay, statistics),
+            TimeToTgidPercent(statistics.delay_sched(), delay, statistics),
+            TimeToTgidPercent(statistics.delay_mem(), delay, statistics),
+            TimeToTgidPercent(statistics.delay_total(), delay, statistics));
+        if (n > 0 && --n == 0) break;
+      }
+      second = false;
+
+      if (cycles > 0 && --cycles == 0) break;
+    }
+    first = false;
+    sleep(delay);
+  }
+
+  return 0;
+}
diff --git a/iotop/tasklist.cpp b/iotop/tasklist.cpp
new file mode 100644
index 00000000..c1041a46
--- /dev/null
+++ b/iotop/tasklist.cpp
@@ -0,0 +1,65 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/types.h>
+#include <dirent.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <base/stringprintf.h>
+
+#include "tasklist.h"
+
+template<typename Func>
+static bool ScanPidsInDir(std::string name, Func f) {
+  std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(name.c_str()), closedir);
+  if (!dir) {
+    return false;
+  }
+
+  dirent* entry;
+  while ((entry = readdir(dir.get())) != nullptr) {
+    if (isdigit(entry->d_name[0])) {
+      pid_t pid = atoi(entry->d_name);
+      f(pid);
+    }
+  }
+
+  return true;
+}
+
+bool TaskList::Scan(std::map<pid_t, std::vector<pid_t>>& tgid_map) {
+  tgid_map.clear();
+
+  return ScanPidsInDir("/proc", [&tgid_map](pid_t tgid) {
+    std::vector<pid_t> pid_list;
+    if (ScanPid(tgid, pid_list)) {
+      tgid_map.insert({tgid, pid_list});
+    }
+  });
+}
+
+bool TaskList::ScanPid(pid_t tgid, std::vector<pid_t>& pid_list) {
+  std::string filename = android::base::StringPrintf("/proc/%d/task", tgid);
+
+  return ScanPidsInDir(filename, [&pid_list](pid_t pid) {
+    pid_list.push_back(pid);
+  });
+}
diff --git a/iotop/tasklist.h b/iotop/tasklist.h
new file mode 100644
index 00000000..1a19c8fb
--- /dev/null
+++ b/iotop/tasklist.h
@@ -0,0 +1,30 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <map>
+#include <vector>
+
+#ifndef _IOTOP_TASKLIST_H
+#define _IOTOP_TASKLIST_H
+
+class TaskList {
+public:
+  static bool Scan(std::map<pid_t, std::vector<pid_t>>&);
+
+private:
+  TaskList() {}
+  static bool ScanPid(pid_t pid, std::vector<pid_t>&);
+};
+
+#endif // _IOTOP_TASKLIST_H
diff --git a/iotop/taskstats.cpp b/iotop/taskstats.cpp
new file mode 100644
index 00000000..0c397dc5
--- /dev/null
+++ b/iotop/taskstats.cpp
@@ -0,0 +1,228 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <linux/taskstats.h>
+#include <netlink/socket.h>
+#include <netlink/genl/ctrl.h>
+#include <netlink/genl/genl.h>
+
+#include <algorithm>
+#include <memory>
+
+#include <base/logging.h>
+
+#include "taskstats.h"
+
+TaskstatsSocket::TaskstatsSocket()
+    : nl_(nullptr, nl_socket_free), family_id_(0) {
+}
+
+bool TaskstatsSocket::Open() {
+  std::unique_ptr<nl_sock, decltype(&nl_socket_free)> nl(
+      nl_socket_alloc(), nl_socket_free);
+  if (!nl.get()) {
+    LOG(FATAL) << "Failed to allocate netlink socket";
+  }
+
+  int ret = genl_connect(nl.get());
+  if (ret < 0) {
+    LOG(FATAL) << nl_geterror(ret) << std::endl << "Unable to open netlink socket (are you root?)";
+  }
+
+  int family_id = genl_ctrl_resolve(nl.get(), TASKSTATS_GENL_NAME);
+  if (family_id < 0) {
+    LOG(FATAL) << nl_geterror(family_id) << std::endl << "Unable to determine taskstats family id (does your kernel support taskstats?)";
+  }
+
+  nl_ = std::move(nl);
+  family_id_ = family_id;
+
+  return true;
+}
+
+void TaskstatsSocket::Close() {
+  nl_.reset();
+}
+
+struct TaskStatsRequest {
+  pid_t requested_pid;
+  taskstats stats;
+};
+
+static pid_t ParseAggregateTaskStats(nlattr* attr, int attr_size,
+                                     taskstats* stats) {
+  pid_t received_pid = -1;
+  nla_for_each_attr(attr, attr, attr_size, attr_size) {
+    switch (nla_type(attr)) {
+    case TASKSTATS_TYPE_PID:
+    case TASKSTATS_TYPE_TGID:
+      received_pid = nla_get_u32(attr);
+      break;
+    case TASKSTATS_TYPE_STATS:
+    {
+      int len = static_cast<int>(sizeof(*stats));
+      len = std::min(len, nla_len(attr));
+      nla_memcpy(stats, attr, len);
+      return received_pid;
+    }
+    default:
+      LOG(ERROR) << "unexpected attribute inside AGGR";
+      return -1;
+    }
+  }
+
+  return -1;
+}
+
+static int ParseTaskStats(nl_msg* msg, void* arg) {
+  TaskStatsRequest* taskstats_request = static_cast<TaskStatsRequest*>(arg);
+  genlmsghdr* gnlh = static_cast<genlmsghdr*>(nlmsg_data(nlmsg_hdr(msg)));
+  nlattr* attr = genlmsg_attrdata(gnlh, 0);
+
+  switch (nla_type(attr)) {
+  case TASKSTATS_TYPE_AGGR_PID:
+  case TASKSTATS_TYPE_AGGR_TGID:
+    nlattr* nested_attr = static_cast<nlattr*>(nla_data(attr));
+    taskstats stats;
+    pid_t ret;
+
+    ret = ParseAggregateTaskStats(nested_attr, nla_len(attr), &stats);
+    if (ret < 0) {
+      LOG(ERROR) << "Bad AGGR_PID contents";
+    } else if (ret == taskstats_request->requested_pid) {
+      taskstats_request->stats = stats;
+    } else {
+      LOG(WARNING) << "got taskstats for unexpected pid " << ret <<
+          " (expected " << taskstats_request->requested_pid << ", continuing...";
+    }
+  }
+  return NL_OK;
+}
+
+bool TaskstatsSocket::GetStats(int pid, int type, TaskStatistics& stats) {
+  TaskStatsRequest taskstats_request = TaskStatsRequest();
+  taskstats_request.requested_pid = pid;
+
+  std::unique_ptr<nl_msg, decltype(&nlmsg_free)> message(nlmsg_alloc(),
+                                                         nlmsg_free);
+
+  genlmsg_put(message.get(), NL_AUTO_PID, NL_AUTO_SEQ, family_id_, 0, 0,
+              TASKSTATS_CMD_GET, TASKSTATS_VERSION);
+  nla_put_u32(message.get(), type, pid);
+
+  int result = nl_send_auto_complete(nl_.get(), message.get());
+  if (result < 0) {
+    return false;
+  }
+
+  std::unique_ptr<nl_cb, decltype(&nl_cb_put)> callbacks(
+      nl_cb_alloc(NL_CB_DEFAULT), nl_cb_put);
+  nl_cb_set(callbacks.get(), NL_CB_VALID, NL_CB_CUSTOM, &ParseTaskStats,
+            static_cast<void*>(&taskstats_request));
+
+  result = nl_recvmsgs(nl_.get(), callbacks.get());
+  if (result < 0) {
+    return false;
+  }
+  nl_wait_for_ack(nl_.get());
+
+  stats = TaskStatistics(taskstats_request.stats);
+
+  return true;
+}
+
+bool TaskstatsSocket::GetPidStats(int pid, TaskStatistics& stats) {
+  return GetStats(pid, TASKSTATS_CMD_ATTR_PID, stats);
+}
+
+bool TaskstatsSocket::GetTgidStats(int tgid, TaskStatistics& stats) {
+  bool ret = GetStats(tgid, TASKSTATS_CMD_ATTR_TGID, stats);
+  if (ret) {
+    stats.set_pid(tgid);
+  }
+  return ret;
+}
+
+TaskStatistics::TaskStatistics(const taskstats& taskstats_stats) {
+  comm_ = std::string(taskstats_stats.ac_comm);
+  pid_ = taskstats_stats.ac_pid;
+
+  uid_ = taskstats_stats.ac_uid;
+  gid_ = taskstats_stats.ac_gid;
+  pid_ = taskstats_stats.ac_pid;
+  ppid_ = taskstats_stats.ac_ppid;
+
+  cpu_delay_count_ = taskstats_stats.cpu_count;
+  cpu_delay_ns_ = taskstats_stats.cpu_delay_total;
+
+  block_io_delay_count_ = taskstats_stats.blkio_count;
+  block_io_delay_ns_ = taskstats_stats.blkio_delay_total;
+
+  swap_in_delay_count_ = taskstats_stats.swapin_count;
+  swap_in_delay_ns_ = taskstats_stats.swapin_delay_total;
+
+  reclaim_delay_count_ = taskstats_stats.freepages_count;
+  reclaim_delay_ns_ = taskstats_stats.freepages_delay_total;
+
+  total_delay_ns_ =
+      cpu_delay_ns_ + block_io_delay_ns_ + swap_in_delay_ns_ + reclaim_delay_ns_;
+
+  cpu_time_real_ = taskstats_stats.cpu_run_real_total;
+  cpu_time_virtual_ = taskstats_stats.cpu_run_virtual_total;
+
+  read_bytes_ = taskstats_stats.read_bytes;
+  write_bytes_ = taskstats_stats.write_bytes;
+  read_write_bytes_ = read_bytes_ + write_bytes_;
+  cancelled_write_bytes_ = taskstats_stats.cancelled_write_bytes;
+  threads_ = 1;
+}
+
+void TaskStatistics::AddPidToTgid(const TaskStatistics& pid_statistics) {
+  // tgid statistics already contain delay values totalled across all pids
+  // only add IO statistics
+  read_bytes_            += pid_statistics.read_bytes_;
+  write_bytes_           += pid_statistics.write_bytes_;
+  read_write_bytes_      += pid_statistics.read_write_bytes_;
+  cancelled_write_bytes_ += pid_statistics.cancelled_write_bytes_;
+  if (pid_ == pid_statistics.pid_) {
+    comm_ = pid_statistics.comm_;
+    uid_ = pid_statistics.uid_;
+    gid_ = pid_statistics.pid_;
+    ppid_ = pid_statistics.ppid_;
+  } else {
+    threads_++;
+  }
+}
+
+// Store new statistics and return the delta from the old statistics
+TaskStatistics TaskStatistics::Update(const TaskStatistics& new_statistics) {
+  TaskStatistics delta = new_statistics;
+  delta.cpu_delay_count_       -= cpu_delay_count_;
+  delta.cpu_delay_ns_          -= cpu_delay_ns_;
+  delta.block_io_delay_count_  -= block_io_delay_count_;
+  delta.block_io_delay_ns_     -= block_io_delay_ns_;
+  delta.swap_in_delay_count_   -= swap_in_delay_count_;
+  delta.swap_in_delay_ns_      -= swap_in_delay_ns_;
+  delta.reclaim_delay_count_   -= reclaim_delay_count_;
+  delta.reclaim_delay_ns_      -= reclaim_delay_ns_;
+  delta.total_delay_ns_        -= total_delay_ns_;
+  delta.cpu_time_real_         -= cpu_time_real_;
+  delta.cpu_time_virtual_      -= cpu_time_virtual_;
+  delta.read_bytes_            -= read_bytes_;
+  delta.write_bytes_           -= write_bytes_;
+  delta.read_write_bytes_      -= read_write_bytes_;
+  delta.cancelled_write_bytes_ -= cancelled_write_bytes_;
+  *this = new_statistics;
+  return delta;
+}
diff --git a/iotop/taskstats.h b/iotop/taskstats.h
new file mode 100644
index 00000000..f5ad2d20
--- /dev/null
+++ b/iotop/taskstats.h
@@ -0,0 +1,94 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <memory>
+#include <string>
+
+#include <stdint.h>
+
+#ifndef _IOTOP_TASKSTATS_H
+#define _IOTOP_TASKSTATS_H
+
+struct nl_sock;
+struct taskstats;
+
+class TaskStatistics {
+public:
+  TaskStatistics(const taskstats&);
+  TaskStatistics() = default;
+  TaskStatistics(const TaskStatistics&) = default;
+  void AddPidToTgid(const TaskStatistics&);
+  TaskStatistics Update(const TaskStatistics&);
+
+  pid_t pid() const { return pid_; }
+  const std::string& comm() const { return comm_; }
+  uint64_t read() const { return read_bytes_; }
+  uint64_t write() const { return write_bytes_; }
+  uint64_t read_write() const { return read_write_bytes_; }
+  uint64_t delay_io() const { return block_io_delay_ns_; }
+  uint64_t delay_swap() const { return swap_in_delay_ns_; }
+  uint64_t delay_sched() const { return cpu_delay_ns_; }
+  uint64_t delay_mem() const { return reclaim_delay_ns_; }
+  uint64_t delay_total() const { return total_delay_ns_; }
+  int threads() const { return threads_; }
+
+  void set_pid(pid_t pid) { pid_ = pid; }
+
+private:
+  std::string comm_;
+  uid_t uid_;
+  gid_t gid_;
+  pid_t pid_;
+  pid_t ppid_;
+
+  uint64_t cpu_delay_count_;
+  uint64_t cpu_delay_ns_;
+
+  uint64_t block_io_delay_count_;
+  uint64_t block_io_delay_ns_;
+
+  uint64_t swap_in_delay_count_;
+  uint64_t swap_in_delay_ns_;
+
+  uint64_t reclaim_delay_count_;
+  uint64_t reclaim_delay_ns_;
+
+  uint64_t total_delay_ns_;
+
+  uint64_t cpu_time_real_;
+  uint64_t cpu_time_virtual_;
+
+  uint64_t read_bytes_;
+  uint64_t write_bytes_;
+  uint64_t read_write_bytes_;
+  uint64_t cancelled_write_bytes_;
+
+  int threads_;
+};
+
+class TaskstatsSocket {
+public:
+  TaskstatsSocket();
+  bool Open();
+  void Close();
+
+  bool GetPidStats(int, TaskStatistics&);
+  bool GetTgidStats(int, TaskStatistics&);
+private:
+  bool GetStats(int, int, TaskStatistics& stats);
+  std::unique_ptr<nl_sock, void(*)(nl_sock*)> nl_;
+  int family_id_;
+};
+
+#endif // _IOTOP_TASKSTATS_H