erts: Add the +sfwi system flag

+sfwi Interval
    Set scheduler forced wakeup interval. All run queues will be scanned
    each Interval milliseconds. While there are sleeping schedulers in
    the system, one scheduler will be woken for each non-empty run queue
    found. An Interval of zero disables this feature, which also is the
    default.

    This feature has been introduced as a temporary workaround for lengthy
    executing native code, and native code that do not bump reductions
    properly in OTP. When these bugs have be fixed the +sfwi flag will
    be removed.

Conflicts:

	erts/doc/src/erl.xml
	erts/etc/common/erlexec.c

1 files changed, 16 insertions, 0 deletions

diff --git a/erts/emulator/beam/erl_init.c b/erts/emulator/beam/erl_init.c
index 1eb3dba240..7f52b111ac 100644
--- a/erts/emulator/beam/erl_init.c
+++ b/erts/emulator/beam/erl_init.c
@@ -1240,6 +1240,22 @@ erl_start(int argc, char **argv)
 			("suggested scheduler thread stack size %d kilo words\n",
 			 erts_sched_thread_suggested_stack_size));
 	    }
+	    else if (has_prefix("fwi", sub_param)) {
+		long val;
+		arg = get_arg(sub_param+3, argv[i+1], &i);
+		errno = 0;
+		val = strtol(arg, NULL, 10);
+		if (errno != 0 || val < 0) {
+		    erts_fprintf(stderr,
+				 "bad scheduler forced wakeup "
+				 "interval %s\n",
+				 arg);
+		    erts_usage();
+		}
+#ifdef ERTS_SMP
+		erts_runq_supervision_interval = val;
+#endif
+	    }
 	    else {
 		erts_fprintf(stderr, "bad scheduling option %s\n", argv[i]);
 		erts_usage();