[Openmp-commits] [PATCH] D19030: [ITTNOTIFY] Correct barrier imbalance time in case of tasks

[Jonathan Peyton via Openmp-commits]

jlpeyton created this revision.
jlpeyton added reviewers: omalyshe, AndreyChurbanov.
jlpeyton added a subscriber: openmp-commits.
jlpeyton set the repository for this revision to rL LLVM.

ittnotify fix for barrier imbalance time in case tasks exist. In the current implementation, task execution time is included into aggregated time on a barrier.  This fix calculates task execution time and corrects the arrive time by subtracing the task execution time.

Since __kmp_invoke_task() can not only be called on a barrier, the field th.th_bar_arrive_time is used to check if the function was called at the barrier (th.th_bar_arrive_time != 0). So for this check, th_bar_arrive_time is set to zero right after the value is used on the barrier.

Repository:
  rL LLVM

http://reviews.llvm.org/D19030

Files:
  runtime/src/kmp_barrier.cpp
  runtime/src/kmp_tasking.c

Index: runtime/src/kmp_tasking.c
===================================================================
--- runtime/src/kmp_tasking.c
+++ runtime/src/kmp_tasking.c
@@ -1103,6 +1103,7 @@
 __kmp_invoke_task( kmp_int32 gtid, kmp_task_t *task, kmp_taskdata_t * current_task )
 {
     kmp_taskdata_t * taskdata = KMP_TASK_TO_TASKDATA(task);
+    kmp_uint64 cur_time;
 #if OMP_40_ENABLED
     int discard = 0 /* false */;
 #endif
@@ -1126,6 +1127,13 @@
          }
 #endif
 
+#if USE_ITT_BUILD && USE_ITT_NOTIFY
+    if(__kmp_forkjoin_frames_mode == 3) {
+        // Get the current time stamp to measure task execution time to correct barrier imbalance time
+        cur_time = __itt_get_timestamp();
+    }
+#endif
+
 #if OMP_41_ENABLED
     // Proxy tasks are not handled by the runtime
     if ( taskdata->td_flags.proxy != TASK_PROXY )
@@ -1219,6 +1227,15 @@
 #endif
        __kmp_task_finish( gtid, task, current_task );
 
+#if USE_ITT_BUILD && USE_ITT_NOTIFY
+    // Barrier imbalance - correct arrive time after the task finished
+    if(__kmp_forkjoin_frames_mode == 3) {
+        kmp_info_t *this_thr = __kmp_threads [ gtid ];
+        if(this_thr->th.th_bar_arrive_time) {
+            this_thr->th.th_bar_arrive_time += (__itt_get_timestamp() - cur_time);
+        }
+    }
+#endif
     KA_TRACE(30, ("__kmp_invoke_task(exit): T#%d completed task %p, resuming task %p\n",
                   gtid, taskdata, current_task) );
     return;
Index: runtime/src/kmp_barrier.cpp
===================================================================
--- runtime/src/kmp_barrier.cpp
+++ runtime/src/kmp_barrier.cpp
@@ -1198,8 +1198,11 @@
                     if( __itt_metadata_add_ptr ) {
                         // Initialize with master's wait time
                         kmp_uint64 delta = cur_time - this_thr->th.th_bar_arrive_time;
+                        // Set arrive time to zero to be able to check it in __kmp_invoke_task(); the same is done inside the loop below
+                        this_thr->th.th_bar_arrive_time = 0;
                         for (i=1; i<nproc; ++i) {
                             delta += ( cur_time - other_threads[i]->th.th_bar_arrive_time );
+                            other_threads[i]->th.th_bar_arrive_time = 0;
                         }
                         __kmp_itt_metadata_imbalance(gtid, this_thr->th.th_frame_time, cur_time, delta, (kmp_uint64)( reduce != NULL));
                     }
@@ -1489,8 +1492,11 @@
                 if( __itt_metadata_add_ptr ) {
                     // Initialize with master's wait time
                     kmp_uint64 delta = cur_time - this_thr->th.th_bar_arrive_time;
+                    // Set arrive time to zero to be able to check it in __kmp_invoke_task(); the same is done inside the loop below
+                    this_thr->th.th_bar_arrive_time = 0;
                     for (i=1; i<nproc; ++i) {
                         delta += ( cur_time - other_threads[i]->th.th_bar_arrive_time );
+                        other_threads[i]->th.th_bar_arrive_time = 0;
                     }
                     __kmp_itt_metadata_imbalance(gtid, this_thr->th.th_frame_time, cur_time, delta, 0);
                 }


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