[mirror_frr.git] / lib / workqueue.c

/*
 * Quagga Work Queue Support.
 *
 * Copyright (C) 2005 Sun Microsystems, Inc.
 *
 * This file is part of GNU Zebra.
 *
 * Quagga is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * Quagga is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>
#include "thread.h"
#include "memory.h"
#include "workqueue.h"
#include "linklist.h"
#include "command.h"
#include "log.h"

DEFINE_MTYPE(LIB, WORK_QUEUE, "Work queue")
DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_ITEM, "Work queue item")
DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_NAME, "Work queue name string")

/* master list of work_queues */
static struct list _work_queues;
/* pointer primarily to avoid an otherwise harmless warning on
 * ALL_LIST_ELEMENTS_RO
 */
static struct list *work_queues = &_work_queues;

#define WORK_QUEUE_MIN_GRANULARITY 1

static struct work_queue_item *work_queue_item_new(struct work_queue *wq)
{
	struct work_queue_item *item;
	assert(wq);

	item = XCALLOC(MTYPE_WORK_QUEUE_ITEM, sizeof(struct work_queue_item));

	return item;
}

static void work_queue_item_free(struct work_queue_item *item)
{
	XFREE(MTYPE_WORK_QUEUE_ITEM, item);
	return;
}

static void work_queue_item_remove(struct work_queue *wq,
				   struct work_queue_item *item)
{
	assert(item && item->data);

	/* call private data deletion callback if needed */
	if (wq->spec.del_item_data)
		wq->spec.del_item_data(wq, item->data);

	work_queue_item_dequeue(wq, item);

	work_queue_item_free(item);

	return;
}

/* create new work queue */
struct work_queue *work_queue_new(struct thread_master *m,
				  const char *queue_name)
{
	struct work_queue *new;

	new = XCALLOC(MTYPE_WORK_QUEUE, sizeof(struct work_queue));

	if (new == NULL)
		return new;

	new->name = XSTRDUP(MTYPE_WORK_QUEUE_NAME, queue_name);
	new->master = m;
	SET_FLAG(new->flags, WQ_UNPLUGGED);

	STAILQ_INIT(&new->items);

	listnode_add(work_queues, new);

	new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;

	/* Default values, can be overriden by caller */
	new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
	new->spec.yield = THREAD_YIELD_TIME_SLOT;

	return new;
}

void work_queue_free_original(struct work_queue *wq)
{
	if (wq->thread != NULL)
		thread_cancel(wq->thread);

	while (!work_queue_empty(wq)) {
		struct work_queue_item *item = work_queue_last_item(wq);

		work_queue_item_remove(wq, item);
	}

	listnode_delete(work_queues, wq);

	XFREE(MTYPE_WORK_QUEUE_NAME, wq->name);
	XFREE(MTYPE_WORK_QUEUE, wq);
	return;
}

void work_queue_free_and_null(struct work_queue **wq)
{
	work_queue_free_original(*wq);
	*wq = NULL;
}

bool work_queue_is_scheduled(struct work_queue *wq)
{
	return (wq->thread != NULL);
}

static int work_queue_schedule(struct work_queue *wq, unsigned int delay)
{
	/* if appropriate, schedule work queue thread */
	if (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) && (wq->thread == NULL)
	    && !work_queue_empty(wq)) {
		wq->thread = NULL;
		thread_add_timer_msec(wq->master, work_queue_run, wq, delay,
				      &wq->thread);
		/* set thread yield time, if needed */
		if (wq->thread && wq->spec.yield != THREAD_YIELD_TIME_SLOT)
			thread_set_yield_time(wq->thread, wq->spec.yield);
		return 1;
	} else
		return 0;
}

void work_queue_add(struct work_queue *wq, void *data)
{
	struct work_queue_item *item;

	assert(wq);

	if (!(item = work_queue_item_new(wq))) {
		zlog_err("%s: unable to get new queue item", __func__);
		return;
	}

	item->data = data;
	work_queue_item_enqueue(wq, item);

	work_queue_schedule(wq, wq->spec.hold);

	return;
}

static void work_queue_item_requeue(struct work_queue *wq,
				    struct work_queue_item *item)
{
	work_queue_item_dequeue(wq, item);

	/* attach to end of list */
	work_queue_item_enqueue(wq, item);
}

DEFUN (show_work_queues,
       show_work_queues_cmd,
       "show work-queues",
       SHOW_STR
       "Work Queue information\n")
{
	struct listnode *node;
	struct work_queue *wq;

	vty_out(vty, "%c %8s %5s %8s %8s %21s\n", ' ', "List", "(ms) ",
		"Q. Runs", "Yields", "Cycle Counts   ");
	vty_out(vty, "%c %8s %5s %8s %8s %7s %6s %8s %6s %s\n", 'P', "Items",
		"Hold", "Total", "Total", "Best", "Gran.", "Total", "Avg.",
		"Name");

	for (ALL_LIST_ELEMENTS_RO(work_queues, node, wq)) {
		vty_out(vty, "%c %8d %5d %8ld %8ld %7d %6d %8ld %6u %s\n",
			(CHECK_FLAG(wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
			work_queue_item_count(wq), wq->spec.hold, wq->runs,
			wq->yields, wq->cycles.best, wq->cycles.granularity,
			wq->cycles.total,
			(wq->runs) ? (unsigned int)(wq->cycles.total / wq->runs)
				   : 0,
			wq->name);
	}

	return CMD_SUCCESS;
}

void workqueue_cmd_init(void)
{
	install_element(VIEW_NODE, &show_work_queues_cmd);
}

/* 'plug' a queue: Stop it from being scheduled,
 * ie: prevent the queue from draining.
 */
void work_queue_plug(struct work_queue *wq)
{
	if (wq->thread)
		thread_cancel(wq->thread);

	wq->thread = NULL;

	UNSET_FLAG(wq->flags, WQ_UNPLUGGED);
}

/* unplug queue, schedule it again, if appropriate
 * Ie: Allow the queue to be drained again
 */
void work_queue_unplug(struct work_queue *wq)
{
	SET_FLAG(wq->flags, WQ_UNPLUGGED);

	/* if thread isnt already waiting, add one */
	work_queue_schedule(wq, wq->spec.hold);
}

/* timer thread to process a work queue
 * will reschedule itself if required,
 * otherwise work_queue_item_add
 */
int work_queue_run(struct thread *thread)
{
	struct work_queue *wq;
	struct work_queue_item *item, *titem;
	wq_item_status ret;
	unsigned int cycles = 0;
	char yielded = 0;

	wq = THREAD_ARG(thread);

	assert(wq);

	wq->thread = NULL;

	/* calculate cycle granularity:
	 * list iteration == 1 run
	 * listnode processing == 1 cycle
	 * granularity == # cycles between checks whether we should yield.
	 *
	 * granularity should be > 0, and can increase slowly after each run to
	 * provide some hysteris, but not past cycles.best or 2*cycles.
	 *
	 * Best: starts low, can only increase
	 *
	 * Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
	 *              if we run to end of time slot, can increase otherwise
	 *              by a small factor.
	 *
	 * We could use just the average and save some work, however we want to
	 * be
	 * able to adjust quickly to CPU pressure. Average wont shift much if
	 * daemon has been running a long time.
	 */
	if (wq->cycles.granularity == 0)
		wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;

	STAILQ_FOREACH_SAFE (item, &wq->items, wq, titem) {
		assert(item && item->data);

		/* dont run items which are past their allowed retries */
		if (item->ran > wq->spec.max_retries) {
			/* run error handler, if any */
			if (wq->spec.errorfunc)
				wq->spec.errorfunc(wq, item->data);
			work_queue_item_remove(wq, item);
			continue;
		}

		/* run and take care of items that want to be retried
		 * immediately */
		do {
			ret = wq->spec.workfunc(wq, item->data);
			item->ran++;
		} while ((ret == WQ_RETRY_NOW)
			 && (item->ran < wq->spec.max_retries));

		switch (ret) {
		case WQ_QUEUE_BLOCKED: {
			/* decrement item->ran again, cause this isn't an item
			 * specific error, and fall through to WQ_RETRY_LATER
			 */
			item->ran--;
		}
		case WQ_RETRY_LATER: {
			goto stats;
		}
		case WQ_REQUEUE: {
			item->ran--;
			work_queue_item_requeue(wq, item);
			/* If a single node is being used with a meta-queue
			 * (e.g., zebra),
			 * update the next node as we don't want to exit the
			 * thread and
			 * reschedule it after every node. By definition,
			 * WQ_REQUEUE is
			 * meant to continue the processing; the yield logic
			 * will kick in
			 * to terminate the thread when time has exceeded.
			 */
			if (titem == NULL)
				titem = item;
			break;
		}
		case WQ_RETRY_NOW:
		/* a RETRY_NOW that gets here has exceeded max_tries, same as
		 * ERROR */
		case WQ_ERROR: {
			if (wq->spec.errorfunc)
				wq->spec.errorfunc(wq, item);
		}
		/* fallthru */
		case WQ_SUCCESS:
		default: {
			work_queue_item_remove(wq, item);
			break;
		}
		}

		/* completed cycle */
		cycles++;

		/* test if we should yield */
		if (!(cycles % wq->cycles.granularity)
		    && thread_should_yield(thread)) {
			yielded = 1;
			goto stats;
		}
	}

stats:

#define WQ_HYSTERESIS_FACTOR 4

	/* we yielded, check whether granularity should be reduced */
	if (yielded && (cycles < wq->cycles.granularity)) {
		wq->cycles.granularity =
			((cycles > 0) ? cycles : WORK_QUEUE_MIN_GRANULARITY);
	}
	/* otherwise, should granularity increase? */
	else if (cycles >= (wq->cycles.granularity)) {
		if (cycles > wq->cycles.best)
			wq->cycles.best = cycles;

		/* along with yielded check, provides hysteresis for granularity
		 */
		if (cycles > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR
			      * WQ_HYSTERESIS_FACTOR))
			wq->cycles.granularity *=
				WQ_HYSTERESIS_FACTOR; /* quick ramp-up */
		else if (cycles
			 > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR))
			wq->cycles.granularity += WQ_HYSTERESIS_FACTOR;
	}
#undef WQ_HYSTERIS_FACTOR

	wq->runs++;
	wq->cycles.total += cycles;
	if (yielded)
		wq->yields++;

#if 0
  printf ("%s: cycles %d, new: best %d, worst %d\n",
            __func__, cycles, wq->cycles.best, wq->cycles.granularity);
#endif

	/* Is the queue done yet? If it is, call the completion callback. */
	if (!work_queue_empty(wq))
		work_queue_schedule(wq, 0);
	else if (wq->spec.completion_func)
		wq->spec.completion_func(wq);

	return 0;
}
Commit	Line	Data
d62a17ae	1	/*
354d119a	2	* Quagga Work Queue Support.
	3	*
	4	* Copyright (C) 2005 Sun Microsystems, Inc.
	5	*
	6	* This file is part of GNU Zebra.
	7	*
	8	* Quagga is free software; you can redistribute it and/or modify it
	9	* under the terms of the GNU General Public License as published by the
	10	* Free Software Foundation; either version 2, or (at your option) any
	11	* later version.
	12	*
	13	* Quagga is distributed in the hope that it will be useful, but
	14	* WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* General Public License for more details.
	17	*
896014f4 DL	18	* You should have received a copy of the GNU General Public License along
	19	* with this program; see the file COPYING; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
354d119a	21	*/
354d119a	22
7a2fbbf0	23	#include <zebra.h>
354d119a	24	#include "thread.h"
	25	#include "memory.h"
	26	#include "workqueue.h"
	27	#include "linklist.h"
	28	#include "command.h"
	29	#include "log.h"
	30
d62a17ae	31	DEFINE_MTYPE(LIB, WORK_QUEUE, "Work queue")
4a1ab8e4 DL	32	DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_ITEM, "Work queue item")
	33	DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_NAME, "Work queue name string")
	34
354d119a	35	/* master list of work_queues */
24873f0c	36	static struct list _work_queues;
1f9a9fff	37	/* pointer primarily to avoid an otherwise harmless warning on
24873f0c DS	38	* ALL_LIST_ELEMENTS_RO
	39	*/
	40	static struct list *work_queues = &_work_queues;
354d119a	41
	42	#define WORK_QUEUE_MIN_GRANULARITY 1
	43
d62a17ae	44	static struct work_queue_item work_queue_item_new(struct work_queue wq)
354d119a	45	{
d62a17ae	46	struct work_queue_item *item;
d62a17ae	47	assert(wq);
354d119a	48
d62a17ae	49	item = XCALLOC(MTYPE_WORK_QUEUE_ITEM, sizeof(struct work_queue_item));
	50
	51	return item;
354d119a	52	}
354d119a	53
d62a17ae	54	static void work_queue_item_free(struct work_queue_item *item)
354d119a	55	{
d62a17ae	56	XFREE(MTYPE_WORK_QUEUE_ITEM, item);
d62a17ae	57	return;
354d119a	58	}
354d119a	59
da7f979a DS	60	static void work_queue_item_remove(struct work_queue *wq,
	61	struct work_queue_item *item)
	62	{
	63	assert(item && item->data);
	64
	65	/* call private data deletion callback if needed */
	66	if (wq->spec.del_item_data)
	67	wq->spec.del_item_data(wq, item->data);
	68
	69	work_queue_item_dequeue(wq, item);
	70
	71	work_queue_item_free(item);
	72
	73	return;
	74	}
	75
354d119a	76	/* create new work queue */
d62a17ae	77	struct work_queue work_queue_new(struct thread_master m,
d62a17ae	78	const char *queue_name)
354d119a	79	{
d62a17ae	80	struct work_queue *new;
	81
	82	new = XCALLOC(MTYPE_WORK_QUEUE, sizeof(struct work_queue));
	83
	84	if (new == NULL)
	85	return new;
	86
	87	new->name = XSTRDUP(MTYPE_WORK_QUEUE_NAME, queue_name);
	88	new->master = m;
	89	SET_FLAG(new->flags, WQ_UNPLUGGED);
	90
f104f6c1	91	STAILQ_INIT(&new->items);
d62a17ae	92
	93	listnode_add(work_queues, new);
	94
	95	new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
	96
	97	/* Default values, can be overriden by caller */
	98	new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
	99	new->spec.yield = THREAD_YIELD_TIME_SLOT;
	100
	101	return new;
354d119a	102	}
354d119a	103
e208c8f9	104	void work_queue_free_original(struct work_queue *wq)
354d119a	105	{
d62a17ae	106	if (wq->thread != NULL)
	107	thread_cancel(wq->thread);
	108
da7f979a DS	109	while (!work_queue_empty(wq)) {
	110	struct work_queue_item *item = work_queue_last_item(wq);
	111
	112	work_queue_item_remove(wq, item);
	113	}
	114
d62a17ae	115	listnode_delete(work_queues, wq);
	116
	117	XFREE(MTYPE_WORK_QUEUE_NAME, wq->name);
	118	XFREE(MTYPE_WORK_QUEUE, wq);
	119	return;
354d119a	120	}
354d119a	121
e208c8f9 DS	122	void work_queue_free_and_null(struct work_queue **wq)
	123	{
	124	work_queue_free_original(*wq);
	125	*wq = NULL;
	126	}
	127
d62a17ae	128	bool work_queue_is_scheduled(struct work_queue *wq)
86582682	129	{
d62a17ae	130	return (wq->thread != NULL);
86582682 PJ	131	}
86582682 PJ	132
d62a17ae	133	static int work_queue_schedule(struct work_queue *wq, unsigned int delay)
269d74fd	134	{
d62a17ae	135	/* if appropriate, schedule work queue thread */
996c9314 LB	136	if (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) && (wq->thread == NULL)
996c9314 LB	137	&& !work_queue_empty(wq)) {
d62a17ae	138	wq->thread = NULL;
	139	thread_add_timer_msec(wq->master, work_queue_run, wq, delay,
	140	&wq->thread);
	141	/* set thread yield time, if needed */
	142	if (wq->thread && wq->spec.yield != THREAD_YIELD_TIME_SLOT)
	143	thread_set_yield_time(wq->thread, wq->spec.yield);
	144	return 1;
	145	} else
	146	return 0;
269d74fd	147	}
d62a17ae	148
d62a17ae	149	void work_queue_add(struct work_queue wq, void data)
354d119a	150	{
d62a17ae	151	struct work_queue_item *item;
	152
	153	assert(wq);
	154
	155	if (!(item = work_queue_item_new(wq))) {
	156	zlog_err("%s: unable to get new queue item", __func__);
	157	return;
	158	}
	159
	160	item->data = data;
f104f6c1	161	work_queue_item_enqueue(wq, item);
d62a17ae	162
	163	work_queue_schedule(wq, wq->spec.hold);
	164
	165	return;
354d119a	166	}
354d119a	167
996c9314 LB	168	static void work_queue_item_requeue(struct work_queue *wq,
996c9314 LB	169	struct work_queue_item *item)
354d119a	170	{
f104f6c1 JB	171	work_queue_item_dequeue(wq, item);
	172
	173	/* attach to end of list */
	174	work_queue_item_enqueue(wq, item);
354d119a	175	}
354d119a	176
49d41a26 DS	177	DEFUN (show_work_queues,
	178	show_work_queues_cmd,
	179	"show work-queues",
	180	SHOW_STR
	181	"Work Queue information\n")
354d119a	182	{
d62a17ae	183	struct listnode *node;
	184	struct work_queue *wq;
	185
	186	vty_out(vty, "%c %8s %5s %8s %8s %21s\n", ' ', "List", "(ms) ",
	187	"Q. Runs", "Yields", "Cycle Counts ");
	188	vty_out(vty, "%c %8s %5s %8s %8s %7s %6s %8s %6s %s\n", 'P', "Items",
	189	"Hold", "Total", "Total", "Best", "Gran.", "Total", "Avg.",
	190	"Name");
	191
	192	for (ALL_LIST_ELEMENTS_RO(work_queues, node, wq)) {
	193	vty_out(vty, "%c %8d %5d %8ld %8ld %7d %6d %8ld %6u %s\n",
	194	(CHECK_FLAG(wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
f104f6c1	195	work_queue_item_count(wq), wq->spec.hold, wq->runs,
d62a17ae	196	wq->yields, wq->cycles.best, wq->cycles.granularity,
	197	wq->cycles.total,
	198	(wq->runs) ? (unsigned int)(wq->cycles.total / wq->runs)
	199	: 0,
	200	wq->name);
	201	}
	202
	203	return CMD_SUCCESS;
354d119a	204	}
354d119a	205
d62a17ae	206	void workqueue_cmd_init(void)
0b84f294	207	{
d62a17ae	208	install_element(VIEW_NODE, &show_work_queues_cmd);
0b84f294 DL	209	}
0b84f294 DL	210
269d74fd	211	/* 'plug' a queue: Stop it from being scheduled,
	212	* ie: prevent the queue from draining.
	213	*/
d62a17ae	214	void work_queue_plug(struct work_queue *wq)
269d74fd	215	{
d62a17ae	216	if (wq->thread)
	217	thread_cancel(wq->thread);
	218
	219	wq->thread = NULL;
	220
	221	UNSET_FLAG(wq->flags, WQ_UNPLUGGED);
269d74fd	222	}
	223
	224	/* unplug queue, schedule it again, if appropriate
	225	* Ie: Allow the queue to be drained again
	226	*/
d62a17ae	227	void work_queue_unplug(struct work_queue *wq)
269d74fd	228	{
d62a17ae	229	SET_FLAG(wq->flags, WQ_UNPLUGGED);
269d74fd	230
d62a17ae	231	/* if thread isnt already waiting, add one */
d62a17ae	232	work_queue_schedule(wq, wq->spec.hold);
269d74fd	233	}
269d74fd	234
354d119a	235	/* timer thread to process a work queue
354d119a	236	* will reschedule itself if required,
d62a17ae	237	* otherwise work_queue_item_add
354d119a	238	*/
d62a17ae	239	int work_queue_run(struct thread *thread)
354d119a	240	{
d62a17ae	241	struct work_queue *wq;
f104f6c1	242	struct work_queue_item item, titem;
d62a17ae	243	wq_item_status ret;
d62a17ae	244	unsigned int cycles = 0;
d62a17ae	245	char yielded = 0;
	246
	247	wq = THREAD_ARG(thread);
d62a17ae	248
f104f6c1	249	assert(wq);
d62a17ae	250
b575a12c A	251	wq->thread = NULL;
b575a12c A	252
d62a17ae	253	/* calculate cycle granularity:
	254	* list iteration == 1 run
	255	* listnode processing == 1 cycle
	256	* granularity == # cycles between checks whether we should yield.
	257	*
	258	* granularity should be > 0, and can increase slowly after each run to
	259	* provide some hysteris, but not past cycles.best or 2*cycles.
	260	*
	261	* Best: starts low, can only increase
	262	*
	263	* Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
	264	* if we run to end of time slot, can increase otherwise
	265	* by a small factor.
	266	*
	267	* We could use just the average and save some work, however we want to
	268	* be
	269	* able to adjust quickly to CPU pressure. Average wont shift much if
	270	* daemon has been running a long time.
	271	*/
	272	if (wq->cycles.granularity == 0)
	273	wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
	274
a2addae8	275	STAILQ_FOREACH_SAFE (item, &wq->items, wq, titem) {
d62a17ae	276	assert(item && item->data);
	277
	278	/* dont run items which are past their allowed retries */
	279	if (item->ran > wq->spec.max_retries) {
	280	/* run error handler, if any */
	281	if (wq->spec.errorfunc)
	282	wq->spec.errorfunc(wq, item->data);
f104f6c1	283	work_queue_item_remove(wq, item);
d62a17ae	284	continue;
	285	}
	286
	287	/* run and take care of items that want to be retried
	288	* immediately */
	289	do {
	290	ret = wq->spec.workfunc(wq, item->data);
	291	item->ran++;
	292	} while ((ret == WQ_RETRY_NOW)
	293	&& (item->ran < wq->spec.max_retries));
	294
	295	switch (ret) {
	296	case WQ_QUEUE_BLOCKED: {
	297	/* decrement item->ran again, cause this isn't an item
	298	* specific error, and fall through to WQ_RETRY_LATER
	299	*/
	300	item->ran--;
	301	}
	302	case WQ_RETRY_LATER: {
	303	goto stats;
	304	}
	305	case WQ_REQUEUE: {
	306	item->ran--;
f104f6c1	307	work_queue_item_requeue(wq, item);
d62a17ae	308	/* If a single node is being used with a meta-queue
	309	* (e.g., zebra),
	310	* update the next node as we don't want to exit the
	311	* thread and
	312	* reschedule it after every node. By definition,
	313	* WQ_REQUEUE is
	314	* meant to continue the processing; the yield logic
	315	* will kick in
	316	* to terminate the thread when time has exceeded.
	317	*/
f104f6c1 JB	318	if (titem == NULL)
f104f6c1 JB	319	titem = item;
d62a17ae	320	break;
	321	}
	322	case WQ_RETRY_NOW:
	323	/* a RETRY_NOW that gets here has exceeded max_tries, same as
	324	* ERROR */
	325	case WQ_ERROR: {
	326	if (wq->spec.errorfunc)
	327	wq->spec.errorfunc(wq, item);
	328	}
	329	/* fallthru */
	330	case WQ_SUCCESS:
	331	default: {
f104f6c1	332	work_queue_item_remove(wq, item);
d62a17ae	333	break;
	334	}
	335	}
	336
	337	/* completed cycle */
	338	cycles++;
	339
	340	/* test if we should yield */
	341	if (!(cycles % wq->cycles.granularity)
	342	&& thread_should_yield(thread)) {
	343	yielded = 1;
	344	goto stats;
	345	}
354d119a	346	}
354d119a	347
	348	stats:
	349
3322055b	350	#define WQ_HYSTERESIS_FACTOR 4
354d119a	351
d62a17ae	352	/* we yielded, check whether granularity should be reduced */
	353	if (yielded && (cycles < wq->cycles.granularity)) {
	354	wq->cycles.granularity =
	355	((cycles > 0) ? cycles : WORK_QUEUE_MIN_GRANULARITY);
	356	}
	357	/* otherwise, should granularity increase? */
	358	else if (cycles >= (wq->cycles.granularity)) {
	359	if (cycles > wq->cycles.best)
	360	wq->cycles.best = cycles;
	361
	362	/* along with yielded check, provides hysteresis for granularity
	363	*/
	364	if (cycles > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR
	365	* WQ_HYSTERESIS_FACTOR))
	366	wq->cycles.granularity *=
	367	WQ_HYSTERESIS_FACTOR; /* quick ramp-up */
	368	else if (cycles
	369	> (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR))
	370	wq->cycles.granularity += WQ_HYSTERESIS_FACTOR;
	371	}
354d119a	372	#undef WQ_HYSTERIS_FACTOR
d62a17ae	373
	374	wq->runs++;
	375	wq->cycles.total += cycles;
	376	if (yielded)
	377	wq->yields++;
354d119a	378
	379	#if 0
	380	printf ("%s: cycles %d, new: best %d, worst %d\n",
	381	__func__, cycles, wq->cycles.best, wq->cycles.granularity);
	382	#endif
d62a17ae	383
d62a17ae	384	/* Is the queue done yet? If it is, call the completion callback. */
f104f6c1	385	if (!work_queue_empty(wq))
d62a17ae	386	work_queue_schedule(wq, 0);
	387	else if (wq->spec.completion_func)
	388	wq->spec.completion_func(wq);
	389
	390	return 0;
354d119a	391	}