Miscellaneous #2482

dbms/src/Common/CurrentThread.h

@@ -56,7 +56,7 @@ public:
     static void attachQueryContext(Context & query_context);
 
     /// You must call one of these methods when create a query child thread:
-    /// Add current thread to a group associated with thr thread group
+    /// Add current thread to a group associated with the thread group
     static void attachTo(const ThreadGroupStatusPtr & thread_group);
     /// Is useful for a ThreadPool tasks
     static void attachToIfDetached(const ThreadGroupStatusPtr & thread_group);

dbms/src/Common/ProfileEvents.h

@@ -59,9 +59,10 @@ namespace ProfileEvents
             } while (current != nullptr);
         }
 
+        /// Every single value is fetched atomically, but not all values as a whole.
         Counters getPartiallyAtomicSnapshot() const;
 
-        /// Reset metrics and parent
+        /// Reset all counters to zero and reset parent.
         void reset();
 
         /// Get parent (thread unsafe)

dbms/src/Common/TaskStatsInfoGetter.cpp

@@ -174,7 +174,7 @@ bool TaskStatsInfoGetter::getStatImpl(int tid, ::taskstats & out_stats, bool thr
     {
         ::nlmsgerr * err = static_cast<::nlmsgerr *>(NLMSG_DATA(&msg));
         if (throw_on_error)
-            throw Exception("Can't get Netlink response, error=" + std::to_string(err->error), ErrorCodes::NETLINK_ERROR);
+            throw Exception("Can't get Netlink response, error: " + std::to_string(err->error), ErrorCodes::NETLINK_ERROR);
         else
             return false;
     }
@@ -198,16 +198,16 @@ bool TaskStatsInfoGetter::getStatImpl(int tid, ::taskstats & out_stats, bool thr
             {
                 if (na->nla_type == TASKSTATS_TYPE_STATS)
                 {
-                    ::taskstats *ts = static_cast<::taskstats *>(NLA_DATA(na));
+                    ::taskstats * ts = static_cast<::taskstats *>(NLA_DATA(na));
                     out_stats = *ts;
                 }
 
                 len2 += NLA_ALIGN(na->nla_len);
-                na = reinterpret_cast<::nlattr *>((char *) na + len2);
+                na = reinterpret_cast<::nlattr *>(reinterpret_cast<char *>(na) + len2);
             }
         }
 
-        na = reinterpret_cast<::nlattr *>((char *) GENLMSG_DATA(&msg) + len);
+        na = reinterpret_cast<::nlattr *>(reinterpret_cast<char *>(GENLMSG_DATA(&msg)) + len);
     }
 
     return true;
@@ -215,13 +215,13 @@ bool TaskStatsInfoGetter::getStatImpl(int tid, ::taskstats & out_stats, bool thr
 
 void TaskStatsInfoGetter::getStat(::taskstats & stat, int tid)
 {
-    tid = tid < 0 ? getDefaultTid() : tid;
+    tid = tid < 0 ? getDefaultTID() : tid;
     getStatImpl(tid, stat, true);
 }
 
 bool TaskStatsInfoGetter::tryGetStat(::taskstats & stat, int tid)
 {
-    tid = tid < 0 ? getDefaultTid() : tid;
+    tid = tid < 0 ? getDefaultTID() : tid;
     return getStatImpl(tid, stat, false);
 }
 
@@ -233,10 +233,11 @@ TaskStatsInfoGetter::~TaskStatsInfoGetter()
 
 int TaskStatsInfoGetter::getCurrentTID()
 {
+    /// This call is always successful. - man gettid
     return static_cast<int>(syscall(SYS_gettid));
 }
 
-int TaskStatsInfoGetter::getDefaultTid()
+int TaskStatsInfoGetter::getDefaultTID()
 {
     if (default_tid < 0)
         default_tid = getCurrentTID();

dbms/src/Common/TaskStatsInfoGetter.h

@@ -10,11 +10,10 @@ namespace DB
 class Exception;
 
 
-/// Get taskstat infor from OS kernel via Netlink protocol
+/// Get taskstat info from OS kernel via Netlink protocol.
 class TaskStatsInfoGetter
 {
 public:
-
     TaskStatsInfoGetter();
     TaskStatsInfoGetter(const TaskStatsInfoGetter &) = delete;
 
@@ -30,9 +29,8 @@ public:
     static bool checkProcessHasRequiredPermissions();
 
 private:
-
     /// Caches current thread tid to avoid extra sys calls
-    int getDefaultTid();
+    int getDefaultTID();
     int default_tid = -1;
 
     bool getStatImpl(int tid, ::taskstats & out_stats, bool throw_on_error = false);

dbms/src/Interpreters/tests/internal_iotop.cpp

@@ -99,7 +99,7 @@ void do_io(size_t id)
     get_info.getStat(stat, tid);
     {
         std::lock_guard<std::mutex> lock(mutex);
-        std::cerr << "#" << id << ", tid " << tid << ", step2\n" << stat << "\n";
+        std::cerr << "#" << id << ", tid " << tid << ", step3\n" << stat << "\n";
     }
 
     Poco::File(path_dst).remove(false);
@@ -113,16 +113,12 @@ void test_perf()
     TaskStatsInfoGetter get_info;
 
     rusage rusage;
-    timespec ts;
 
     constexpr size_t num_samples = 1000000;
     {
         Stopwatch watch;
         for (size_t i = 0; i < num_samples; ++i)
-        {
             getrusage(RUSAGE_THREAD, &rusage);
-            clock_gettime(CLOCK_MONOTONIC, &ts);
-        }
 
         auto ms = watch.elapsedMilliseconds();
         if (ms > 0)
@@ -151,13 +147,9 @@ try
     ThreadPool pool(num_threads);
     for (size_t i = 0; i < num_threads; ++i)
         pool.schedule([i]() { do_io(i); });
-
     pool.wait();
 
-
     test_perf();
-
-
     return 0;
 }
 catch (...)