lib/libzpool/taskq.c

   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 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 #include <sys/zfs_context.h>
  27
  28 int taskq_now;
  29 taskq_t *system_taskq;
  30
  31 typedef struct task {
  32         struct task     *task_next;
  33         struct task     *task_prev;
  34         task_func_t     *task_func;
  35         void            *task_arg;
  36 } task_t;
  37
  38 #define TASKQ_ACTIVE    0x00010000
  39
  40 struct taskq {
  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         task_t          *tq_freelist;
  53         task_t          tq_task;
  54 };
  55
  56 static task_t *
  57 task_alloc(taskq_t *tq, int tqflags)
  58 {
  59         task_t *t;
  60
  61         if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
  62                 tq->tq_freelist = t->task_next;
  63         } else {
  64                 mutex_exit(&tq->tq_lock);
  65                 if (tq->tq_nalloc >= tq->tq_maxalloc) {
  66                         if (!(tqflags & KM_SLEEP)) {
  67                                 mutex_enter(&tq->tq_lock);
  68                                 return (NULL);
  69                         }
  70                         /*
  71                          * We don't want to exceed tq_maxalloc, but we can't
  72                          * wait for other tasks to complete (and thus free up
  73                          * task structures) without risking deadlock with
  74                          * the caller.  So, we just delay for one second
  75                          * to throttle the allocation rate.
  76                          */
  77                         delay(hz);
  78                 }
  79                 t = kmem_alloc(sizeof (task_t), tqflags);
  80                 mutex_enter(&tq->tq_lock);
  81                 if (t != NULL)
  82                         tq->tq_nalloc++;
  83         }
  84         return (t);
  85 }
  86
  87 static void
  88 task_free(taskq_t *tq, task_t *t)
  89 {
  90         if (tq->tq_nalloc <= tq->tq_minalloc) {
  91                 t->task_next = tq->tq_freelist;
  92                 tq->tq_freelist = t;
  93         } else {
  94                 tq->tq_nalloc--;
  95                 mutex_exit(&tq->tq_lock);
  96                 kmem_free(t, sizeof (task_t));
  97                 mutex_enter(&tq->tq_lock);
  98         }
  99 }
 100
 101 taskqid_t
 102 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 103 {
 104         task_t *t;
 105
 106         if (taskq_now) {
 107                 func(arg);
 108                 return (1);
 109         }
 110
 111         mutex_enter(&tq->tq_lock);
 112         ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 113         if ((t = task_alloc(tq, tqflags)) == NULL) {
 114                 mutex_exit(&tq->tq_lock);
 115                 return (0);
 116         }
 117         t->task_next = &tq->tq_task;
 118         t->task_prev = tq->tq_task.task_prev;
 119         t->task_next->task_prev = t;
 120         t->task_prev->task_next = t;
 121         t->task_func = func;
 122         t->task_arg = arg;
 123         cv_signal(&tq->tq_dispatch_cv);
 124         mutex_exit(&tq->tq_lock);
 125         return (1);
 126 }
 127
 128 void
 129 taskq_wait(taskq_t *tq)
 130 {
 131         mutex_enter(&tq->tq_lock);
 132         while (tq->tq_task.task_next != &tq->tq_task || tq->tq_active != 0)
 133                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 134         mutex_exit(&tq->tq_lock);
 135 }
 136
 137 static void *
 138 taskq_thread(void *arg)
 139 {
 140         taskq_t *tq = arg;
 141         task_t *t;
 142
 143         mutex_enter(&tq->tq_lock);
 144         while (tq->tq_flags & TASKQ_ACTIVE) {
 145                 if ((t = tq->tq_task.task_next) == &tq->tq_task) {
 146                         if (--tq->tq_active == 0)
 147                                 cv_broadcast(&tq->tq_wait_cv);
 148                         cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 149                         tq->tq_active++;
 150                         continue;
 151                 }
 152                 t->task_prev->task_next = t->task_next;
 153                 t->task_next->task_prev = t->task_prev;
 154                 mutex_exit(&tq->tq_lock);
 155
 156                 rw_enter(&tq->tq_threadlock, RW_READER);
 157                 t->task_func(t->task_arg);
 158                 rw_exit(&tq->tq_threadlock);
 159
 160                 mutex_enter(&tq->tq_lock);
 161                 task_free(tq, t);
 162         }
 163         tq->tq_nthreads--;
 164         cv_broadcast(&tq->tq_wait_cv);
 165         mutex_exit(&tq->tq_lock);
 166         return (NULL);
 167 }
 168
 169 /*ARGSUSED*/
 170 taskq_t *
 171 taskq_create(const char *name, int nthreads, pri_t pri,
 172         int minalloc, int maxalloc, uint_t flags)
 173 {
 174         taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 175         int t;
 176
 177         if (flags & TASKQ_THREADS_CPU_PCT) {
 178                 int pct;
 179                 ASSERT3S(nthreads, >=, 0);
 180                 ASSERT3S(nthreads, <=, 100);
 181                 pct = MIN(nthreads, 100);
 182                 pct = MAX(pct, 0);
 183
 184                 nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
 185                 nthreads = MAX(nthreads, 1);    /* need at least 1 thread */
 186         } else {
 187                 ASSERT3S(nthreads, >=, 1);
 188         }
 189
 190         rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 191         mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 192         cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 193         cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 194         tq->tq_flags = flags | TASKQ_ACTIVE;
 195         tq->tq_active = nthreads;
 196         tq->tq_nthreads = nthreads;
 197         tq->tq_minalloc = minalloc;
 198         tq->tq_maxalloc = maxalloc;
 199         tq->tq_task.task_next = &tq->tq_task;
 200         tq->tq_task.task_prev = &tq->tq_task;
 201         tq->tq_threadlist = kmem_alloc(nthreads * sizeof (thread_t), KM_SLEEP);
 202
 203         if (flags & TASKQ_PREPOPULATE) {
 204                 mutex_enter(&tq->tq_lock);
 205                 while (minalloc-- > 0)
 206                         task_free(tq, task_alloc(tq, KM_SLEEP));
 207                 mutex_exit(&tq->tq_lock);
 208         }
 209
 210         for (t = 0; t < nthreads; t++)
 211                 (void) thr_create(0, 0, taskq_thread,
 212                     tq, THR_BOUND, &tq->tq_threadlist[t]);
 213
 214         return (tq);
 215 }
 216
 217 void
 218 taskq_destroy(taskq_t *tq)
 219 {
 220         int t;
 221         int nthreads = tq->tq_nthreads;
 222
 223         taskq_wait(tq);
 224
 225         mutex_enter(&tq->tq_lock);
 226
 227         tq->tq_flags &= ~TASKQ_ACTIVE;
 228         cv_broadcast(&tq->tq_dispatch_cv);
 229
 230         while (tq->tq_nthreads != 0)
 231                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 232
 233         tq->tq_minalloc = 0;
 234         while (tq->tq_nalloc != 0) {
 235                 ASSERT(tq->tq_freelist != NULL);
 236                 task_free(tq, task_alloc(tq, KM_SLEEP));
 237         }
 238
 239         mutex_exit(&tq->tq_lock);
 240
 241         for (t = 0; t < nthreads; t++)
 242                 (void) thr_join(tq->tq_threadlist[t], NULL, NULL);
 243
 244         kmem_free(tq->tq_threadlist, nthreads * sizeof (thread_t));
 245
 246         rw_destroy(&tq->tq_threadlock);
 247         mutex_destroy(&tq->tq_lock);
 248         cv_destroy(&tq->tq_dispatch_cv);
 249         cv_destroy(&tq->tq_wait_cv);
 250
 251         kmem_free(tq, sizeof (taskq_t));
 252 }
 253
 254 int
 255 taskq_member(taskq_t *tq, void *t)
 256 {
 257         int i;
 258
 259         if (taskq_now)
 260                 return (1);
 261
 262         for (i = 0; i < tq->tq_nthreads; i++)
 263                 if (tq->tq_threadlist[i] == (thread_t)(uintptr_t)t)
 264                         return (1);
 265
 266         return (0);
 267 }
 268
 269 void
 270 system_taskq_init(void)
 271 {
 272         system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
 273             TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 274 }