Add STARPU_MPI_NOBIND environment variable

ChangeLog

@@ -52,6 +52,7 @@ StarPU 1.3.5 (git revision xxx)
 
 Small changes:
   * Move MPI cache functions into the public API
+  * Add STARPU_MPI_NOBIND environment variable.
 
 StarPU 1.3.4 (git revision c37a5d024cd997596da41f765557c58099baf896)
 ====================================================================

doc/doxygen/chapters/501_environment_variables.doxy

@@ -255,6 +255,14 @@ it to -1 (the default value) will use a reserved CPU, subtracted from the CPU
 workers.
 </dd>
 
+<dt>STARPU_MPI_NOBIND</dt>
+<dd>
+\anchor STARPU_MPI_NOBIND
+\addindex __env__STARPU_MPI_NOBIND
+Setting it to non-zero will prevent StarPU from binding the MPI to
+a separate core. This is for instance useful when running the testsuite on a single system.
+</dd>
+
 <dt>STARPU_WORKERS_CUDAID</dt>
 <dd>
 \anchor STARPU_WORKERS_CUDAID

mpi/src/mpi/starpu_mpi_mpi.c

@@ -1206,14 +1206,14 @@ static void *_starpu_mpi_progress_thread_func(void *arg)
 		_starpu_mpi_thread_cpuid = starpu_get_next_bindid(STARPU_THREAD_ACTIVE, NULL, 0);
 	}
 
-	if (starpu_bind_thread_on(_starpu_mpi_thread_cpuid, STARPU_THREAD_ACTIVE, "MPI") < 0)
+	if (!_starpu_mpi_nobind && starpu_bind_thread_on(_starpu_mpi_thread_cpuid, STARPU_THREAD_ACTIVE, "MPI") < 0)
 	{
 		char hostname[65];
 		gethostname(hostname, sizeof(hostname));
 		_STARPU_DISP("[%s] No core was available for the MPI thread. You should use STARPU_RESERVE_NCPU to leave one core available for MPI, or specify one core less in STARPU_NCPU\n", hostname);
 	}
 	_starpu_mpi_do_initialize(argc_argv);
-	if (_starpu_mpi_thread_cpuid >= 0)
+	if (!_starpu_mpi_nobind && _starpu_mpi_thread_cpuid >= 0)
 		/* In case MPI changed the binding */
 		starpu_bind_thread_on(_starpu_mpi_thread_cpuid, STARPU_THREAD_ACTIVE, "MPI");
 #else

mpi/src/nmad/starpu_mpi_nmad.c

@@ -451,7 +451,7 @@ static void *_starpu_mpi_progress_thread_func(void *arg)
 	struct _starpu_mpi_argc_argv *argc_argv = (struct _starpu_mpi_argc_argv *) arg;
 
 #ifndef STARPU_SIMGRID
-	if (starpu_bind_thread_on(_starpu_mpi_thread_cpuid, 0, "MPI") < 0)
+	if (!_starpu_mpi_nobind && starpu_bind_thread_on(_starpu_mpi_thread_cpuid, 0, "MPI") < 0)
 	{
 		char hostname[65];
 		gethostname(hostname, sizeof(hostname));
@@ -623,7 +623,7 @@ int _starpu_mpi_progress_init(struct _starpu_mpi_argc_argv *argc_argv)
 	 * required for piom_ltask_set_bound_thread_indexes() */
 	_starpu_mpi_do_initialize(argc_argv);
 
-	if (_starpu_mpi_thread_cpuid < 0)
+	if (!_starpu_mpi_nobind && _starpu_mpi_thread_cpuid < 0)
 	{
 		_starpu_mpi_thread_cpuid = starpu_get_next_bindid(STARPU_THREAD_ACTIVE, NULL, 0);
 	}
@@ -633,7 +633,8 @@ int _starpu_mpi_progress_init(struct _starpu_mpi_argc_argv *argc_argv)
 	/* Tell pioman to use a bound thread for communication progression:
 	 * share the same core as StarPU's MPI thread, the MPI thread has very low activity with NMAD backend */
 	int indexes[1] = { _starpu_mpi_thread_cpuid };
-	piom_ltask_set_bound_thread_indexes(HWLOC_OBJ_PU, indexes, 1);
+	if (!_starpu_mpi_nobind)
+		piom_ltask_set_bound_thread_indexes(HWLOC_OBJ_PU, indexes, 1);
 
 	/* Register some hooks for communication progress if needed */
 	int polling_point_prog, polling_point_idle;

mpi/src/starpu_mpi_private.c

@@ -22,6 +22,7 @@ int _starpu_debug_level_max=0;
 int _starpu_mpi_tag = 42;
 int _starpu_mpi_comm_debug;
 
+int _starpu_mpi_nobind = -1;
 int _starpu_mpi_thread_cpuid = -1;
 int _starpu_mpi_use_prio = 1;
 int _starpu_mpi_fake_world_size = -1;
@@ -62,6 +63,7 @@ void _starpu_mpi_env_init(void)
         _starpu_mpi_comm_debug = starpu_getenv("STARPU_MPI_COMM") != NULL;
 	_starpu_mpi_fake_world_size = starpu_get_env_number("STARPU_MPI_FAKE_SIZE");
 	_starpu_mpi_fake_world_rank = starpu_get_env_number("STARPU_MPI_FAKE_RANK");
+	_starpu_mpi_nobind = starpu_get_env_number_default("STARPU_MPI_NOBIND", 0);
 	_starpu_mpi_thread_cpuid = starpu_get_env_number_default("STARPU_MPI_THREAD_CPUID", -1);
 	_starpu_mpi_use_prio = starpu_get_env_number_default("STARPU_MPI_PRIORITIES", 1);
 	_starpu_mpi_use_coop_sends = starpu_get_env_number_default("STARPU_MPI_COOP_SENDS", 1);

mpi/src/starpu_mpi_private.h

@@ -61,6 +61,7 @@ void _starpu_mpi_set_debug_level_max(int level);
 extern int _starpu_mpi_fake_world_size;
 extern int _starpu_mpi_fake_world_rank;
 extern int _starpu_mpi_use_prio;
+extern int _starpu_mpi_nobind;
 extern int _starpu_mpi_thread_cpuid;
 extern int _starpu_mpi_use_coop_sends;
 extern int _starpu_mpi_mem_throttle;