[Openmp-commits] [PATCH] D123044: [OpenMP] libomp: honor passive wait policy requested in the presence of tasking

[Jonathan Peyton via Phabricator via Openmp-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGc44ba01de7f0: [OpenMP] libomp: honor passive wait policy requested with tasking (authored by AndreyChurbanov, committed by jlpeyton).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D123044/new/

https://reviews.llvm.org/D123044

Files:
  openmp/runtime/src/kmp.h
  openmp/runtime/src/kmp_global.cpp
  openmp/runtime/src/kmp_settings.cpp
  openmp/runtime/src/kmp_tasking.cpp
  openmp/runtime/src/kmp_wait_release.h


Index: openmp/runtime/src/kmp_wait_release.h
===================================================================
--- openmp/runtime/src/kmp_wait_release.h
+++ openmp/runtime/src/kmp_wait_release.h
@@ -609,7 +609,8 @@
       continue;
 
     // Don't suspend if there is a likelihood of new tasks being spawned.
-    if ((task_team != NULL) && TCR_4(task_team->tt.tt_found_tasks))
+    if (task_team != NULL && TCR_4(task_team->tt.tt_found_tasks) &&
+        !__kmp_wpolicy_passive)
       continue;
 
 #if KMP_USE_MONITOR
Index: openmp/runtime/src/kmp_tasking.cpp
===================================================================
--- openmp/runtime/src/kmp_tasking.cpp
+++ openmp/runtime/src/kmp_tasking.cpp
@@ -1909,8 +1909,21 @@
     if (serialize_immediate)
       new_taskdata->td_flags.task_serial = 1;
     __kmp_invoke_task(gtid, new_task, current_task);
+  } else if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME &&
+             __kmp_wpolicy_passive) {
+    kmp_info_t *this_thr = __kmp_threads[gtid];
+    kmp_team_t *team = this_thr->th.th_team;
+    kmp_int32 nthreads = this_thr->th.th_team_nproc;
+    for (int i = 0; i < nthreads; ++i) {
+      kmp_info_t *thread = team->t.t_threads[i];
+      if (thread == this_thr)
+        continue;
+      if (thread->th.th_sleep_loc != NULL) {
+        __kmp_null_resume_wrapper(thread);
+        break; // awake one thread at a time
+      }
+    }
   }
-
   return TASK_CURRENT_NOT_QUEUED;
 }
 
@@ -4282,6 +4295,17 @@
       pass = pass << 1;
 
   } while (!__kmp_give_task(thread, k, ptask, pass));
+
+  if (__kmp_dflt_blocktime != KMP_MAX_BLOCKTIME && __kmp_wpolicy_passive) {
+    // awake at least one thread to execute given task
+    for (int i = 0; i < nthreads; ++i) {
+      thread = team->t.t_threads[i];
+      if (thread->th.th_sleep_loc != NULL) {
+        __kmp_null_resume_wrapper(thread);
+        break;
+      }
+    }
+  }
 }
 
 /*!
Index: openmp/runtime/src/kmp_settings.cpp
===================================================================
--- openmp/runtime/src/kmp_settings.cpp
+++ openmp/runtime/src/kmp_settings.cpp
@@ -812,6 +812,7 @@
       }
     } else if (__kmp_str_match("PASSIVE", 1, value)) {
       __kmp_library = library_throughput;
+      __kmp_wpolicy_passive = true; /* allow sleep while active tasking */
       if (blocktime_str == NULL) {
         // KMP_BLOCKTIME not specified, so set default to 0.
         __kmp_dflt_blocktime = 0;
Index: openmp/runtime/src/kmp_global.cpp
===================================================================
--- openmp/runtime/src/kmp_global.cpp
+++ openmp/runtime/src/kmp_global.cpp
@@ -154,6 +154,7 @@
 kmp_hier_sched_env_t __kmp_hier_scheds = {0, 0, NULL, NULL, NULL};
 #endif
 int __kmp_dflt_blocktime = KMP_DEFAULT_BLOCKTIME;
+bool __kmp_wpolicy_passive = false;
 #if KMP_USE_MONITOR
 int __kmp_monitor_wakeups = KMP_MIN_MONITOR_WAKEUPS;
 int __kmp_bt_intervals = KMP_INTERVALS_FROM_BLOCKTIME(KMP_DEFAULT_BLOCKTIME,
Index: openmp/runtime/src/kmp.h
===================================================================
--- openmp/runtime/src/kmp.h
+++ openmp/runtime/src/kmp.h
@@ -3160,6 +3160,7 @@
                                (__kmpc_threadprivate_cached()) */
 extern int __kmp_dflt_blocktime; /* number of milliseconds to wait before
                                     blocking (env setting) */
+extern bool __kmp_wpolicy_passive; /* explicitly set passive wait policy */
 #if KMP_USE_MONITOR
 extern int
     __kmp_monitor_wakeups; /* number of times monitor wakes up per second */


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