[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;
}

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

	listnode_delete(work_queues, wq);

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

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_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;
}

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);
	wq->thread = NULL;

	assert(wq);

	/* 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	}
	59
	60	/* create new work queue */
d62a17ae	61	struct work_queue work_queue_new(struct thread_master m,
d62a17ae	62	const char *queue_name)
354d119a	63	{
d62a17ae	64	struct work_queue *new;
	65
	66	new = XCALLOC(MTYPE_WORK_QUEUE, sizeof(struct work_queue));
	67
	68	if (new == NULL)
	69	return new;
	70
	71	new->name = XSTRDUP(MTYPE_WORK_QUEUE_NAME, queue_name);
	72	new->master = m;
	73	SET_FLAG(new->flags, WQ_UNPLUGGED);
	74
f104f6c1	75	STAILQ_INIT(&new->items);
d62a17ae	76
	77	listnode_add(work_queues, new);
	78
	79	new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
	80
	81	/* Default values, can be overriden by caller */
	82	new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
	83	new->spec.yield = THREAD_YIELD_TIME_SLOT;
	84
	85	return new;
354d119a	86	}
354d119a	87
d62a17ae	88	void work_queue_free(struct work_queue *wq)
354d119a	89	{
d62a17ae	90	if (wq->thread != NULL)
	91	thread_cancel(wq->thread);
	92
d62a17ae	93	listnode_delete(work_queues, wq);
	94
	95	XFREE(MTYPE_WORK_QUEUE_NAME, wq->name);
	96	XFREE(MTYPE_WORK_QUEUE, wq);
	97	return;
354d119a	98	}
354d119a	99
d62a17ae	100	bool work_queue_is_scheduled(struct work_queue *wq)
86582682	101	{
d62a17ae	102	return (wq->thread != NULL);
86582682 PJ	103	}
86582682 PJ	104
d62a17ae	105	static int work_queue_schedule(struct work_queue *wq, unsigned int delay)
269d74fd	106	{
d62a17ae	107	/* if appropriate, schedule work queue thread */
f104f6c1 JB	108	if (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) && (wq->thread == NULL) &&
f104f6c1 JB	109	!work_queue_empty(wq)) {
d62a17ae	110	wq->thread = NULL;
	111	thread_add_timer_msec(wq->master, work_queue_run, wq, delay,
	112	&wq->thread);
	113	/* set thread yield time, if needed */
	114	if (wq->thread && wq->spec.yield != THREAD_YIELD_TIME_SLOT)
	115	thread_set_yield_time(wq->thread, wq->spec.yield);
	116	return 1;
	117	} else
	118	return 0;
269d74fd	119	}
d62a17ae	120
d62a17ae	121	void work_queue_add(struct work_queue wq, void data)
354d119a	122	{
d62a17ae	123	struct work_queue_item *item;
	124
	125	assert(wq);
	126
	127	if (!(item = work_queue_item_new(wq))) {
	128	zlog_err("%s: unable to get new queue item", __func__);
	129	return;
	130	}
	131
	132	item->data = data;
f104f6c1	133	work_queue_item_enqueue(wq, item);
d62a17ae	134
	135	work_queue_schedule(wq, wq->spec.hold);
	136
	137	return;
354d119a	138	}
354d119a	139
f104f6c1 JB	140	static void work_queue_item_remove(struct work_queue *wq,
f104f6c1 JB	141	struct work_queue_item *item)
354d119a	142	{
d62a17ae	143	assert(item && item->data);
354d119a	144
d62a17ae	145	/* call private data deletion callback if needed */
	146	if (wq->spec.del_item_data)
	147	wq->spec.del_item_data(wq, item->data);
354d119a	148
f104f6c1 JB	149	work_queue_item_dequeue(wq, item);
f104f6c1 JB	150
d62a17ae	151	work_queue_item_free(item);
	152
	153	return;
354d119a	154	}
354d119a	155
f104f6c1	156	static void work_queue_item_requeue(struct work_queue wq, struct work_queue_item item)
354d119a	157	{
f104f6c1 JB	158	work_queue_item_dequeue(wq, item);
	159
	160	/* attach to end of list */
	161	work_queue_item_enqueue(wq, item);
354d119a	162	}
354d119a	163
49d41a26 DS	164	DEFUN (show_work_queues,
	165	show_work_queues_cmd,
	166	"show work-queues",
	167	SHOW_STR
	168	"Work Queue information\n")
354d119a	169	{
d62a17ae	170	struct listnode *node;
	171	struct work_queue *wq;
	172
	173	vty_out(vty, "%c %8s %5s %8s %8s %21s\n", ' ', "List", "(ms) ",
	174	"Q. Runs", "Yields", "Cycle Counts ");
	175	vty_out(vty, "%c %8s %5s %8s %8s %7s %6s %8s %6s %s\n", 'P', "Items",
	176	"Hold", "Total", "Total", "Best", "Gran.", "Total", "Avg.",
	177	"Name");
	178
	179	for (ALL_LIST_ELEMENTS_RO(work_queues, node, wq)) {
	180	vty_out(vty, "%c %8d %5d %8ld %8ld %7d %6d %8ld %6u %s\n",
	181	(CHECK_FLAG(wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
f104f6c1	182	work_queue_item_count(wq), wq->spec.hold, wq->runs,
d62a17ae	183	wq->yields, wq->cycles.best, wq->cycles.granularity,
	184	wq->cycles.total,
	185	(wq->runs) ? (unsigned int)(wq->cycles.total / wq->runs)
	186	: 0,
	187	wq->name);
	188	}
	189
	190	return CMD_SUCCESS;
354d119a	191	}
354d119a	192
d62a17ae	193	void workqueue_cmd_init(void)
0b84f294	194	{
d62a17ae	195	install_element(VIEW_NODE, &show_work_queues_cmd);
0b84f294 DL	196	}
0b84f294 DL	197
269d74fd	198	/* 'plug' a queue: Stop it from being scheduled,
	199	* ie: prevent the queue from draining.
	200	*/
d62a17ae	201	void work_queue_plug(struct work_queue *wq)
269d74fd	202	{
d62a17ae	203	if (wq->thread)
	204	thread_cancel(wq->thread);
	205
	206	wq->thread = NULL;
	207
	208	UNSET_FLAG(wq->flags, WQ_UNPLUGGED);
269d74fd	209	}
	210
	211	/* unplug queue, schedule it again, if appropriate
	212	* Ie: Allow the queue to be drained again
	213	*/
d62a17ae	214	void work_queue_unplug(struct work_queue *wq)
269d74fd	215	{
d62a17ae	216	SET_FLAG(wq->flags, WQ_UNPLUGGED);
269d74fd	217
d62a17ae	218	/* if thread isnt already waiting, add one */
d62a17ae	219	work_queue_schedule(wq, wq->spec.hold);
269d74fd	220	}
269d74fd	221
354d119a	222	/* timer thread to process a work queue
354d119a	223	* will reschedule itself if required,
d62a17ae	224	* otherwise work_queue_item_add
354d119a	225	*/
d62a17ae	226	int work_queue_run(struct thread *thread)
354d119a	227	{
d62a17ae	228	struct work_queue *wq;
f104f6c1	229	struct work_queue_item item, titem;
d62a17ae	230	wq_item_status ret;
d62a17ae	231	unsigned int cycles = 0;
d62a17ae	232	char yielded = 0;
	233
	234	wq = THREAD_ARG(thread);
	235	wq->thread = NULL;
	236
f104f6c1	237	assert(wq);
d62a17ae	238
	239	/* calculate cycle granularity:
	240	* list iteration == 1 run
	241	* listnode processing == 1 cycle
	242	* granularity == # cycles between checks whether we should yield.
	243	*
	244	* granularity should be > 0, and can increase slowly after each run to
	245	* provide some hysteris, but not past cycles.best or 2*cycles.
	246	*
	247	* Best: starts low, can only increase
	248	*
	249	* Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
	250	* if we run to end of time slot, can increase otherwise
	251	* by a small factor.
	252	*
	253	* We could use just the average and save some work, however we want to
	254	* be
	255	* able to adjust quickly to CPU pressure. Average wont shift much if
	256	* daemon has been running a long time.
	257	*/
	258	if (wq->cycles.granularity == 0)
	259	wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
	260
a2addae8	261	STAILQ_FOREACH_SAFE (item, &wq->items, wq, titem) {
d62a17ae	262	assert(item && item->data);
	263
	264	/* dont run items which are past their allowed retries */
	265	if (item->ran > wq->spec.max_retries) {
	266	/* run error handler, if any */
	267	if (wq->spec.errorfunc)
	268	wq->spec.errorfunc(wq, item->data);
f104f6c1	269	work_queue_item_remove(wq, item);
d62a17ae	270	continue;
	271	}
	272
	273	/* run and take care of items that want to be retried
	274	* immediately */
	275	do {
	276	ret = wq->spec.workfunc(wq, item->data);
	277	item->ran++;
	278	} while ((ret == WQ_RETRY_NOW)
	279	&& (item->ran < wq->spec.max_retries));
	280
	281	switch (ret) {
	282	case WQ_QUEUE_BLOCKED: {
	283	/* decrement item->ran again, cause this isn't an item
	284	* specific error, and fall through to WQ_RETRY_LATER
	285	*/
	286	item->ran--;
	287	}
	288	case WQ_RETRY_LATER: {
	289	goto stats;
	290	}
	291	case WQ_REQUEUE: {
	292	item->ran--;
f104f6c1	293	work_queue_item_requeue(wq, item);
d62a17ae	294	/* If a single node is being used with a meta-queue
	295	* (e.g., zebra),
	296	* update the next node as we don't want to exit the
	297	* thread and
	298	* reschedule it after every node. By definition,
	299	* WQ_REQUEUE is
	300	* meant to continue the processing; the yield logic
	301	* will kick in
	302	* to terminate the thread when time has exceeded.
	303	*/
f104f6c1 JB	304	if (titem == NULL)
f104f6c1 JB	305	titem = item;
d62a17ae	306	break;
	307	}
	308	case WQ_RETRY_NOW:
	309	/* a RETRY_NOW that gets here has exceeded max_tries, same as
	310	* ERROR */
	311	case WQ_ERROR: {
	312	if (wq->spec.errorfunc)
	313	wq->spec.errorfunc(wq, item);
	314	}
	315	/* fallthru */
	316	case WQ_SUCCESS:
	317	default: {
f104f6c1	318	work_queue_item_remove(wq, item);
d62a17ae	319	break;
	320	}
	321	}
	322
	323	/* completed cycle */
	324	cycles++;
	325
	326	/* test if we should yield */
	327	if (!(cycles % wq->cycles.granularity)
	328	&& thread_should_yield(thread)) {
	329	yielded = 1;
	330	goto stats;
	331	}
354d119a	332	}
354d119a	333
	334	stats:
	335
3322055b	336	#define WQ_HYSTERESIS_FACTOR 4
354d119a	337
d62a17ae	338	/* we yielded, check whether granularity should be reduced */
	339	if (yielded && (cycles < wq->cycles.granularity)) {
	340	wq->cycles.granularity =
	341	((cycles > 0) ? cycles : WORK_QUEUE_MIN_GRANULARITY);
	342	}
	343	/* otherwise, should granularity increase? */
	344	else if (cycles >= (wq->cycles.granularity)) {
	345	if (cycles > wq->cycles.best)
	346	wq->cycles.best = cycles;
	347
	348	/* along with yielded check, provides hysteresis for granularity
	349	*/
	350	if (cycles > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR
	351	* WQ_HYSTERESIS_FACTOR))
	352	wq->cycles.granularity *=
	353	WQ_HYSTERESIS_FACTOR; /* quick ramp-up */
	354	else if (cycles
	355	> (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR))
	356	wq->cycles.granularity += WQ_HYSTERESIS_FACTOR;
	357	}
354d119a	358	#undef WQ_HYSTERIS_FACTOR
d62a17ae	359
	360	wq->runs++;
	361	wq->cycles.total += cycles;
	362	if (yielded)
	363	wq->yields++;
354d119a	364
	365	#if 0
	366	printf ("%s: cycles %d, new: best %d, worst %d\n",
	367	__func__, cycles, wq->cycles.best, wq->cycles.granularity);
	368	#endif
d62a17ae	369
d62a17ae	370	/* Is the queue done yet? If it is, call the completion callback. */
f104f6c1	371	if (!work_queue_empty(wq))
d62a17ae	372	work_queue_schedule(wq, 0);
	373	else if (wq->spec.completion_func)
	374	wq->spec.completion_func(wq);
	375
	376	return 0;
354d119a	377	}