cddl/contrib/opensolaris/lib/libzpool/common/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 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  */
  29
  30 #include <sys/zfs_context.h>
  31
  32 int taskq_now;
  33 taskq_t *system_taskq;
  34
  35 #define TASKQ_ACTIVE    0x00010000
  36
  37 struct taskq {
  38         kmutex_t        tq_lock;
  39         krwlock_t       tq_threadlock;
  40         kcondvar_t      tq_dispatch_cv;
  41         kcondvar_t      tq_wait_cv;
  42         thread_t        *tq_threadlist;
  43         int             tq_flags;
  44         int             tq_active;
  45         int             tq_nthreads;
  46         int             tq_nalloc;
  47         int             tq_minalloc;
  48         int             tq_maxalloc;
  49         kcondvar_t      tq_maxalloc_cv;
  50         int             tq_maxalloc_wait;
  51         taskq_ent_t     *tq_freelist;
  52         taskq_ent_t     tq_task;
  53 };
  54
  55 static taskq_ent_t *
  56 task_alloc(taskq_t *tq, int tqflags)
  57 {
  58         taskq_ent_t *t;
  59         int rv;
  60
  61 again:  if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
  62                 tq->tq_freelist = t->tqent_next;
  63         } else {
  64                 if (tq->tq_nalloc >= tq->tq_maxalloc) {
  65                         if (!(tqflags & KM_SLEEP))
  66                                 return (NULL);
  67
  68                         /*
  69                          * We don't want to exceed tq_maxalloc, but we can't
  70                          * wait for other tasks to complete (and thus free up
  71                          * task structures) without risking deadlock with
  72                          * the caller.  So, we just delay for one second
  73                          * to throttle the allocation rate. If we have tasks
  74                          * complete before one second timeout expires then
  75                          * taskq_ent_free will signal us and we will
  76                          * immediately retry the allocation.
  77                          */
  78                         tq->tq_maxalloc_wait++;
  79                         rv = cv_timedwait(&tq->tq_maxalloc_cv,
  80                             &tq->tq_lock, ddi_get_lbolt() + hz);
  81                         tq->tq_maxalloc_wait--;
  82                         if (rv > 0)
  83                                 goto again;             /* signaled */
  84                 }
  85                 mutex_exit(&tq->tq_lock);
  86
  87                 t = kmem_alloc(sizeof (taskq_ent_t), tqflags & KM_SLEEP);
  88
  89                 mutex_enter(&tq->tq_lock);
  90                 if (t != NULL)
  91                         tq->tq_nalloc++;
  92         }
  93         return (t);
  94 }
  95
  96 static void
  97 task_free(taskq_t *tq, taskq_ent_t *t)
  98 {
  99         if (tq->tq_nalloc <= tq->tq_minalloc) {
 100                 t->tqent_next = tq->tq_freelist;
 101                 tq->tq_freelist = t;
 102         } else {
 103                 tq->tq_nalloc--;
 104                 mutex_exit(&tq->tq_lock);
 105                 kmem_free(t, sizeof (taskq_ent_t));
 106                 mutex_enter(&tq->tq_lock);
 107         }
 108
 109         if (tq->tq_maxalloc_wait)
 110                 cv_signal(&tq->tq_maxalloc_cv);
 111 }
 112
 113 taskqid_t
 114 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 115 {
 116         taskq_ent_t *t;
 117
 118         if (taskq_now) {
 119                 func(arg);
 120                 return (1);
 121         }
 122
 123         mutex_enter(&tq->tq_lock);
 124         ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 125         if ((t = task_alloc(tq, tqflags)) == NULL) {
 126                 mutex_exit(&tq->tq_lock);
 127                 return (0);
 128         }
 129         if (tqflags & TQ_FRONT) {
 130                 t->tqent_next = tq->tq_task.tqent_next;
 131                 t->tqent_prev = &tq->tq_task;
 132         } else {
 133                 t->tqent_next = &tq->tq_task;
 134                 t->tqent_prev = tq->tq_task.tqent_prev;
 135         }
 136         t->tqent_next->tqent_prev = t;
 137         t->tqent_prev->tqent_next = t;
 138         t->tqent_func = func;
 139         t->tqent_arg = arg;
 140         t->tqent_flags = 0;
 141         cv_signal(&tq->tq_dispatch_cv);
 142         mutex_exit(&tq->tq_lock);
 143         return (1);
 144 }
 145
 146 void
 147 taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 148     taskq_ent_t *t)
 149 {
 150         ASSERT(func != NULL);
 151         ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC));
 152
 153         /*
 154          * Mark it as a prealloc'd task.  This is important
 155          * to ensure that we don't free it later.
 156          */
 157         t->tqent_flags |= TQENT_FLAG_PREALLOC;
 158         /*
 159          * Enqueue the task to the underlying queue.
 160          */
 161         mutex_enter(&tq->tq_lock);
 162
 163         if (flags & TQ_FRONT) {
 164                 t->tqent_next = tq->tq_task.tqent_next;
 165                 t->tqent_prev = &tq->tq_task;
 166         } else {
 167                 t->tqent_next = &tq->tq_task;
 168                 t->tqent_prev = tq->tq_task.tqent_prev;
 169         }
 170         t->tqent_next->tqent_prev = t;
 171         t->tqent_prev->tqent_next = t;
 172         t->tqent_func = func;
 173         t->tqent_arg = arg;
 174         cv_signal(&tq->tq_dispatch_cv);
 175         mutex_exit(&tq->tq_lock);
 176 }
 177
 178 void
 179 taskq_wait(taskq_t *tq)
 180 {
 181         mutex_enter(&tq->tq_lock);
 182         while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)
 183                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 184         mutex_exit(&tq->tq_lock);
 185 }
 186
 187 static void *
 188 taskq_thread(void *arg)
 189 {
 190         taskq_t *tq = arg;
 191         taskq_ent_t *t;
 192         boolean_t prealloc;
 193
 194         mutex_enter(&tq->tq_lock);
 195         while (tq->tq_flags & TASKQ_ACTIVE) {
 196                 if ((t = tq->tq_task.tqent_next) == &tq->tq_task) {
 197                         if (--tq->tq_active == 0)
 198                                 cv_broadcast(&tq->tq_wait_cv);
 199                         cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 200                         tq->tq_active++;
 201                         continue;
 202                 }
 203                 t->tqent_prev->tqent_next = t->tqent_next;
 204                 t->tqent_next->tqent_prev = t->tqent_prev;
 205                 t->tqent_next = NULL;
 206                 t->tqent_prev = NULL;
 207                 prealloc = t->tqent_flags & TQENT_FLAG_PREALLOC;
 208                 mutex_exit(&tq->tq_lock);
 209
 210                 rw_enter(&tq->tq_threadlock, RW_READER);
 211                 t->tqent_func(t->tqent_arg);
 212                 rw_exit(&tq->tq_threadlock);
 213
 214                 mutex_enter(&tq->tq_lock);
 215                 if (!prealloc)
 216                         task_free(tq, t);
 217         }
 218         tq->tq_nthreads--;
 219         cv_broadcast(&tq->tq_wait_cv);
 220         mutex_exit(&tq->tq_lock);
 221         return (NULL);
 222 }
 223
 224 /*ARGSUSED*/
 225 taskq_t *
 226 taskq_create(const char *name, int nthreads, pri_t pri,
 227         int minalloc, int maxalloc, uint_t flags)
 228 {
 229         taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 230         int t;
 231
 232         if (flags & TASKQ_THREADS_CPU_PCT) {
 233                 int pct;
 234                 ASSERT3S(nthreads, >=, 0);
 235                 ASSERT3S(nthreads, <=, 100);
 236                 pct = MIN(nthreads, 100);
 237                 pct = MAX(pct, 0);
 238
 239                 nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
 240                 nthreads = MAX(nthreads, 1);    /* need at least 1 thread */
 241         } else {
 242                 ASSERT3S(nthreads, >=, 1);
 243         }
 244
 245         rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 246         mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 247         cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 248         cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 249         cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
 250         tq->tq_flags = flags | TASKQ_ACTIVE;
 251         tq->tq_active = nthreads;
 252         tq->tq_nthreads = nthreads;
 253         tq->tq_minalloc = minalloc;
 254         tq->tq_maxalloc = maxalloc;
 255         tq->tq_task.tqent_next = &tq->tq_task;
 256         tq->tq_task.tqent_prev = &tq->tq_task;
 257         tq->tq_threadlist = kmem_alloc(nthreads * sizeof (thread_t), KM_SLEEP);
 258
 259         if (flags & TASKQ_PREPOPULATE) {
 260                 mutex_enter(&tq->tq_lock);
 261                 while (minalloc-- > 0)
 262                         task_free(tq, task_alloc(tq, KM_SLEEP));
 263                 mutex_exit(&tq->tq_lock);
 264         }
 265
 266         for (t = 0; t < nthreads; t++)
 267                 (void) thr_create(0, 0, taskq_thread,
 268                     tq, THR_BOUND, &tq->tq_threadlist[t]);
 269
 270         return (tq);
 271 }
 272
 273 void
 274 taskq_destroy(taskq_t *tq)
 275 {
 276         int t;
 277         int nthreads = tq->tq_nthreads;
 278
 279         taskq_wait(tq);
 280
 281         mutex_enter(&tq->tq_lock);
 282
 283         tq->tq_flags &= ~TASKQ_ACTIVE;
 284         cv_broadcast(&tq->tq_dispatch_cv);
 285
 286         while (tq->tq_nthreads != 0)
 287                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 288
 289         tq->tq_minalloc = 0;
 290         while (tq->tq_nalloc != 0) {
 291                 ASSERT(tq->tq_freelist != NULL);
 292                 task_free(tq, task_alloc(tq, KM_SLEEP));
 293         }
 294
 295         mutex_exit(&tq->tq_lock);
 296
 297         for (t = 0; t < nthreads; t++)
 298                 (void) thr_join(tq->tq_threadlist[t], NULL, NULL);
 299
 300         kmem_free(tq->tq_threadlist, nthreads * sizeof (thread_t));
 301
 302         rw_destroy(&tq->tq_threadlock);
 303         mutex_destroy(&tq->tq_lock);
 304         cv_destroy(&tq->tq_dispatch_cv);
 305         cv_destroy(&tq->tq_wait_cv);
 306         cv_destroy(&tq->tq_maxalloc_cv);
 307
 308         kmem_free(tq, sizeof (taskq_t));
 309 }
 310
 311 int
 312 taskq_member(taskq_t *tq, void *t)
 313 {
 314         int i;
 315
 316         if (taskq_now)
 317                 return (1);
 318
 319         for (i = 0; i < tq->tq_nthreads; i++)
 320                 if (tq->tq_threadlist[i] == (thread_t)(uintptr_t)t)
 321                         return (1);
 322
 323         return (0);
 324 }
 325
 326 void
 327 system_taskq_init(void)
 328 {
 329         system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
 330             TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 331 }
 332
 333 void
 334 system_taskq_fini(void)
 335 {
 336         taskq_destroy(system_taskq);
 337         system_taskq = NULL; /* defensive */
 338 }