Taskprocessors: Increase high-water mark

In practical tests, we have seen certain taskprocessors, specifically
Stasis subscription taskprocessors, cross the recently-added high-water
mark and emit a warning. This high-water mark warning is only intended
to be emitted when things have tanked on the system and things are
heading south quickly. In the practical tests, the Stasis taskprocessors
sometimes had a max depth of 180 tasks in them, and Asterisk wasn't in
any danger at all.

As such, this ups the high-water mark to 500 tasks instead. It also
redefines the SIP threadpool request denial number to be a multiple of
the taskprocessor high-water mark.

Change-Id: Ic8d3e9497452fecd768ac427bb6f58aa616eebce

include/asterisk/taskprocessor.h

@@ -56,6 +56,8 @@
 
 struct ast_taskprocessor;
 
+#define AST_TASKPROCESSOR_HIGH_WATER_LEVEL 500
+
 /*!
  * \brief ast_tps_options for specification of taskprocessor options
  *

main/taskprocessor.c

@@ -714,8 +714,6 @@ void *ast_taskprocessor_unreference(struct ast_taskprocessor *tps)
 	return NULL;
 }
 
-#define HIGH_WATER_LEVEL 100
-
 /* push the task into the taskprocessor queue */
 static int taskprocessor_push(struct ast_taskprocessor *tps, struct tps_task *t)
 {
@@ -736,7 +734,7 @@ static int taskprocessor_push(struct ast_taskprocessor *tps, struct tps_task *t)
 	AST_LIST_INSERT_TAIL(&tps->tps_queue, t, list);
 	previous_size = tps->tps_queue_size++;
 
-	if (previous_size >= HIGH_WATER_LEVEL && !tps->high_water_warned) {
+	if (previous_size >= AST_TASKPROCESSOR_HIGH_WATER_LEVEL && !tps->high_water_warned) {
 		ast_log(LOG_WARNING, "The '%s' task processor queue reached %d scheduled tasks.\n",
 			tps->name, previous_size);
 		tps->high_water_warned = 1;

res/res_pjsip/pjsip_distributor.c

@@ -245,7 +245,7 @@ static pjsip_module endpoint_mod = {
 	.on_rx_request = endpoint_lookup,
 };
 
-#define SIP_MAX_QUEUE 500L
+#define SIP_MAX_QUEUE (AST_TASKPROCESSOR_HIGH_WATER_LEVEL * 3)
 
 static pj_bool_t distributor(pjsip_rx_data *rdata)
 {