And STARPU_LIMIT_BANDWIDTH environment variable

ChangeLog

@@ -53,6 +53,7 @@ Small features:
   * Add STARPU_LIMIT_CPU_NUMA_MEM environment variable.
   * Add STARPU_WORKERS_GETBIND environment variable.
   * Add STARPU_SCHED_SIMPLE_DECIDE_ALWAYS modular scheduler flag.
+  * And STARPU_LIMIT_BANDWIDTH environment variable.
 
 StarPU 1.3.3 (git revision 11afc5b007fe1ab1c729b55b47a5a98ef7f3cfad)
 ====================================================================

configure.ac

@@ -190,7 +190,7 @@ if test x$enable_simgrid = xyes ; then
 
 	# Latest functions
 	AC_CHECK_FUNCS([MSG_process_attach sg_actor_attach sg_actor_init sg_actor_set_stacksize MSG_zone_get_hosts sg_zone_get_hosts MSG_process_self_name MSG_process_userdata_init sg_actor_data])
-	AC_CHECK_FUNCS([xbt_mutex_try_acquire smpi_process_set_user_data SMPI_thread_create sg_zone_get_by_name sg_link_name sg_host_route sg_host_self sg_host_list sg_host_speed simcall_process_create sg_config_continue_after_help])
+	AC_CHECK_FUNCS([xbt_mutex_try_acquire smpi_process_set_user_data SMPI_thread_create sg_zone_get_by_name sg_link_name sg_link_bandwidth_set sg_host_route sg_host_self sg_host_list sg_host_speed simcall_process_create sg_config_continue_after_help])
 	AC_CHECK_FUNCS([simgrid_init], [AC_DEFINE([STARPU_SIMGRID_HAVE_SIMGRID_INIT], [1], [Define to 1 if you have the `simgrid_init' function.])])
 	AC_CHECK_FUNCS([xbt_barrier_init], [AC_DEFINE([STARPU_SIMGRID_HAVE_XBT_BARRIER_INIT], [1], [Define to 1 if you have the `xbt_barrier_init' function.])])
 	AC_CHECK_FUNCS([sg_actor_sleep_for sg_actor_self sg_actor_ref sg_host_get_properties sg_host_send_to sg_host_sendto sg_cfg_set_int sg_actor_self_execute sg_actor_execute simgrid_get_clock])

doc/doxygen/chapters/501_environment_variables.doxy

@@ -986,6 +986,23 @@ NUMA nodes used by StarPU. Any \ref STARPU_LIMIT_CPU_NUMA_devid_MEM additionally
 specified will take over STARPU_LIMIT_CPU_NUMA_MEM.
 </dd>
 
+<dt>STARPU_LIMIT_BANDWIDTH</dt>
+<dd>
+\anchor STARPU_LIMIT_BANDWIDTH
+\addindex __env__STARPU_LIMIT_BANDWIDTH
+Specify the maximum available PCI bandwidth of the system in MB/s. This can only
+be effective with simgrid simulation. This allows to easily override the
+bandwidths stored in the platform file generated from measurements on the native
+system. This can be used e.g. for convenient
+
+Specify the maximum number of megabytes that should be available to the
+application on each NUMA node. This is the same as specifying that same amount
+with \ref STARPU_LIMIT_CPU_NUMA_devid_MEM for each NUMA node number. The total
+memory available to StarPU will thus be this amount multiplied by the number of
+NUMA nodes used by StarPU. Any \ref STARPU_LIMIT_CPU_NUMA_devid_MEM additionally
+specified will take over STARPU_LIMIT_BANDWIDTH.
+</dd>
+
 <dt>STARPU_MINIMUM_AVAILABLE_MEM</dt>
 <dd>
 \anchor STARPU_MINIMUM_AVAILABLE_MEM

src/core/perfmodel/perfmodel_bus.c

@@ -80,8 +80,8 @@ struct dev_timing
 };
 
 /* TODO: measure latency */
-static double bandwidth_matrix[STARPU_MAXNODES][STARPU_MAXNODES];
-static double latency_matrix[STARPU_MAXNODES][STARPU_MAXNODES];
+static double bandwidth_matrix[STARPU_MAXNODES][STARPU_MAXNODES]; /* MB/s */
+static double latency_matrix[STARPU_MAXNODES][STARPU_MAXNODES]; /* µs */
 static unsigned was_benchmarked = 0;
 #ifndef STARPU_SIMGRID
 static unsigned ncpus = 0;
@@ -1546,6 +1546,20 @@ static int load_bus_bandwidth_file_content(void)
 				return 0;
 			}
 
+			int limit_bandwidth = starpu_get_env_number("STARPU_LIMIT_BANDWIDTH");
+			if (limit_bandwidth >= 0)
+			{
+#ifndef STARPU_SIMGRID
+				_STARPU_DISP("Warning: STARPU_LIMIT_BANDWIDTH set to %d but simgrid not enabled, thus ignored\n", limit_bandwidth);
+#else
+#ifdef HAVE_SG_LINK_BANDWIDTH_SET
+				bandwidth = limit_bandwidth;
+#else
+				_STARPU_DISP("Warning: STARPU_LIMIT_BANDWIDTH set to %d but this requires simgrid 3.26\n", limit_bandwidth);
+#endif
+#endif
+			}
+
 			bandwidth_matrix[src][dst] = bandwidth;
 
 			/* Look out for \t\n */

src/core/simgrid.c

@@ -337,6 +337,19 @@ void _starpu_start_simgrid(int *argc, char **argv)
 #else
 	MSG_create_environment(path);
 #endif
+	int limit_bandwidth = starpu_get_env_number("STARPU_LIMIT_BANDWIDTH");
+	if (limit_bandwidth >= 0)
+	{
+#ifdef HAVE_SG_LINK_BANDWIDTH_SET
+		sg_link_t *links = sg_link_list();
+		int count = sg_link_count(), i;
+		for (i = 0; i < count; i++) {
+			sg_link_bandwidth_set(links[i], limit_bandwidth * 1000000.);
+		}
+#else
+		_STARPU_DISP("Warning: STARPU_LIMIT_BANDWIDTH set to %d but this requires simgrid 3.26, thus ignored\n", limit_bandwidth);
+#endif
+	}
 
 	simgrid_transfer_cost = starpu_get_env_number_default("STARPU_SIMGRID_TRANSFER_COST", 1);
 }