taskq.c revision 349203 
1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 */
25/*
26 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
27 * Copyright 2012 Garrett D'Amore <garrett@damore.org>.  All rights reserved.
28 * Copyright (c) 2014 by Delphix. All rights reserved.
29 */
30
31#include <sys/zfs_context.h>
32
33int taskq_now;
34taskq_t *system_taskq;
35
36#define	TASKQ_ACTIVE	0x00010000
37#define	TASKQ_NAMELEN	31
38
39struct taskq {
40	char		tq_name[TASKQ_NAMELEN + 1];
41	kmutex_t	tq_lock;
42	krwlock_t	tq_threadlock;
43	kcondvar_t	tq_dispatch_cv;
44	kcondvar_t	tq_wait_cv;
45	thread_t	*tq_threadlist;
46	int		tq_flags;
47	int		tq_active;
48	int		tq_nthreads;
49	int		tq_nalloc;
50	int		tq_minalloc;
51	int		tq_maxalloc;
52	kcondvar_t	tq_maxalloc_cv;
53	int		tq_maxalloc_wait;
54	taskq_ent_t	*tq_freelist;
55	taskq_ent_t	tq_task;
56};
57
58static taskq_ent_t *
59task_alloc(taskq_t *tq, int tqflags)
60{
61	taskq_ent_t *t;
62	int rv;
63
64again:	if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
65		tq->tq_freelist = t->tqent_next;
66	} else {
67		if (tq->tq_nalloc >= tq->tq_maxalloc) {
68			if (!(tqflags & KM_SLEEP))
69				return (NULL);
70
71			/*
72			 * We don't want to exceed tq_maxalloc, but we can't
73			 * wait for other tasks to complete (and thus free up
74			 * task structures) without risking deadlock with
75			 * the caller.  So, we just delay for one second
76			 * to throttle the allocation rate. If we have tasks
77			 * complete before one second timeout expires then
78			 * taskq_ent_free will signal us and we will
79			 * immediately retry the allocation.
80			 */
81			tq->tq_maxalloc_wait++;
82#ifdef __FreeBSD__
83			rv = cv_timedwait(&tq->tq_maxalloc_cv,
84			    &tq->tq_lock, hz);
85#else
86			rv = cv_timedwait(&tq->tq_maxalloc_cv,
87			    &tq->tq_lock, ddi_get_lbolt() + hz);
88#endif
89			tq->tq_maxalloc_wait--;
90			if (rv > 0)
91				goto again;		/* signaled */
92		}
93		mutex_exit(&tq->tq_lock);
94
95		t = kmem_alloc(sizeof (taskq_ent_t), tqflags & KM_SLEEP);
96
97		mutex_enter(&tq->tq_lock);
98		if (t != NULL)
99			tq->tq_nalloc++;
100	}
101	return (t);
102}
103
104static void
105task_free(taskq_t *tq, taskq_ent_t *t)
106{
107	if (tq->tq_nalloc <= tq->tq_minalloc) {
108		t->tqent_next = tq->tq_freelist;
109		tq->tq_freelist = t;
110	} else {
111		tq->tq_nalloc--;
112		mutex_exit(&tq->tq_lock);
113		kmem_free(t, sizeof (taskq_ent_t));
114		mutex_enter(&tq->tq_lock);
115	}
116
117	if (tq->tq_maxalloc_wait)
118		cv_signal(&tq->tq_maxalloc_cv);
119}
120
121taskqid_t
122taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
123{
124	taskq_ent_t *t;
125
126	if (taskq_now) {
127		func(arg);
128		return (1);
129	}
130
131	mutex_enter(&tq->tq_lock);
132	ASSERT(tq->tq_flags & TASKQ_ACTIVE);
133	if ((t = task_alloc(tq, tqflags)) == NULL) {
134		mutex_exit(&tq->tq_lock);
135		return (0);
136	}
137	if (tqflags & TQ_FRONT) {
138		t->tqent_next = tq->tq_task.tqent_next;
139		t->tqent_prev = &tq->tq_task;
140	} else {
141		t->tqent_next = &tq->tq_task;
142		t->tqent_prev = tq->tq_task.tqent_prev;
143	}
144	t->tqent_next->tqent_prev = t;
145	t->tqent_prev->tqent_next = t;
146	t->tqent_func = func;
147	t->tqent_arg = arg;
148	t->tqent_flags = 0;
149	cv_signal(&tq->tq_dispatch_cv);
150	mutex_exit(&tq->tq_lock);
151	return (1);
152}
153
154void
155taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
156    taskq_ent_t *t)
157{
158	ASSERT(func != NULL);
159	ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC));
160
161	/*
162	 * Mark it as a prealloc'd task.  This is important
163	 * to ensure that we don't free it later.
164	 */
165	t->tqent_flags |= TQENT_FLAG_PREALLOC;
166	/*
167	 * Enqueue the task to the underlying queue.
168	 */
169	mutex_enter(&tq->tq_lock);
170
171	if (flags & TQ_FRONT) {
172		t->tqent_next = tq->tq_task.tqent_next;
173		t->tqent_prev = &tq->tq_task;
174	} else {
175		t->tqent_next = &tq->tq_task;
176		t->tqent_prev = tq->tq_task.tqent_prev;
177	}
178	t->tqent_next->tqent_prev = t;
179	t->tqent_prev->tqent_next = t;
180	t->tqent_func = func;
181	t->tqent_arg = arg;
182	cv_signal(&tq->tq_dispatch_cv);
183	mutex_exit(&tq->tq_lock);
184}
185
186void
187taskq_wait(taskq_t *tq)
188{
189	mutex_enter(&tq->tq_lock);
190	while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)
191		cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
192	mutex_exit(&tq->tq_lock);
193}
194
195void
196taskq_wait_id(taskq_t *tq, taskqid_t id)
197{
198        taskq_wait(tq);
199}
200
201static void *
202taskq_thread(void *arg)
203{
204	taskq_t *tq = arg;
205	taskq_ent_t *t;
206	boolean_t prealloc;
207
208	mutex_enter(&tq->tq_lock);
209	while (tq->tq_flags & TASKQ_ACTIVE) {
210		if ((t = tq->tq_task.tqent_next) == &tq->tq_task) {
211			if (--tq->tq_active == 0)
212				cv_broadcast(&tq->tq_wait_cv);
213			cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
214			tq->tq_active++;
215			continue;
216		}
217		t->tqent_prev->tqent_next = t->tqent_next;
218		t->tqent_next->tqent_prev = t->tqent_prev;
219		t->tqent_next = NULL;
220		t->tqent_prev = NULL;
221		prealloc = t->tqent_flags & TQENT_FLAG_PREALLOC;
222		mutex_exit(&tq->tq_lock);
223
224		rw_enter(&tq->tq_threadlock, RW_READER);
225		t->tqent_func(t->tqent_arg);
226		rw_exit(&tq->tq_threadlock);
227
228		mutex_enter(&tq->tq_lock);
229		if (!prealloc)
230			task_free(tq, t);
231	}
232	tq->tq_nthreads--;
233	cv_broadcast(&tq->tq_wait_cv);
234	mutex_exit(&tq->tq_lock);
235	return (NULL);
236}
237
238/*ARGSUSED*/
239taskq_t *
240taskq_create(const char *name, int nthreads, pri_t pri,
241	int minalloc, int maxalloc, uint_t flags)
242{
243	taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
244	int t;
245
246	if (flags & TASKQ_THREADS_CPU_PCT) {
247		int pct;
248		ASSERT3S(nthreads, >=, 0);
249		ASSERT3S(nthreads, <=, 100);
250		pct = MIN(nthreads, 100);
251		pct = MAX(pct, 0);
252
253		nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
254		nthreads = MAX(nthreads, 1);	/* need at least 1 thread */
255	} else {
256		ASSERT3S(nthreads, >=, 1);
257	}
258
259	rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
260	mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
261	cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
262	cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
263	cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
264	(void) strncpy(tq->tq_name, name, TASKQ_NAMELEN + 1);
265	tq->tq_flags = flags | TASKQ_ACTIVE;
266	tq->tq_active = nthreads;
267	tq->tq_nthreads = nthreads;
268	tq->tq_minalloc = minalloc;
269	tq->tq_maxalloc = maxalloc;
270	tq->tq_task.tqent_next = &tq->tq_task;
271	tq->tq_task.tqent_prev = &tq->tq_task;
272	tq->tq_threadlist = kmem_alloc(nthreads * sizeof (thread_t), KM_SLEEP);
273
274	if (flags & TASKQ_PREPOPULATE) {
275		mutex_enter(&tq->tq_lock);
276		while (minalloc-- > 0)
277			task_free(tq, task_alloc(tq, KM_SLEEP));
278		mutex_exit(&tq->tq_lock);
279	}
280
281	for (t = 0; t < nthreads; t++)
282		(void) thr_create(0, 0, taskq_thread,
283		    tq, THR_BOUND, &tq->tq_threadlist[t]);
284
285	return (tq);
286}
287
288void
289taskq_destroy(taskq_t *tq)
290{
291	int t;
292	int nthreads = tq->tq_nthreads;
293
294	taskq_wait(tq);
295
296	mutex_enter(&tq->tq_lock);
297
298	tq->tq_flags &= ~TASKQ_ACTIVE;
299	cv_broadcast(&tq->tq_dispatch_cv);
300
301	while (tq->tq_nthreads != 0)
302		cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
303
304	tq->tq_minalloc = 0;
305	while (tq->tq_nalloc != 0) {
306		ASSERT(tq->tq_freelist != NULL);
307		task_free(tq, task_alloc(tq, KM_SLEEP));
308	}
309
310	mutex_exit(&tq->tq_lock);
311
312	for (t = 0; t < nthreads; t++)
313		(void) thr_join(tq->tq_threadlist[t], NULL, NULL);
314
315	kmem_free(tq->tq_threadlist, nthreads * sizeof (thread_t));
316
317	rw_destroy(&tq->tq_threadlock);
318	mutex_destroy(&tq->tq_lock);
319	cv_destroy(&tq->tq_dispatch_cv);
320	cv_destroy(&tq->tq_wait_cv);
321	cv_destroy(&tq->tq_maxalloc_cv);
322
323	kmem_free(tq, sizeof (taskq_t));
324}
325
326int
327taskq_member(taskq_t *tq, void *t)
328{
329	int i;
330
331	if (taskq_now)
332		return (1);
333
334	for (i = 0; i < tq->tq_nthreads; i++)
335		if (tq->tq_threadlist[i] == (thread_t)(uintptr_t)t)
336			return (1);
337
338	return (0);
339}
340
341void
342system_taskq_init(void)
343{
344	system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
345	    TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
346}
347
348void
349system_taskq_fini(void)
350{
351	taskq_destroy(system_taskq);
352	system_taskq = NULL; /* defensive */
353}
354