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 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         kthread_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                 ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
  63                 tq->tq_freelist = t->tqent_next;
  64         } else {
  65                 if (tq->tq_nalloc >= tq->tq_maxalloc) {
  66                         if (!(tqflags & KM_SLEEP))
  67                                 return (NULL);
  68
  69                         /*
  70                          * We don't want to exceed tq_maxalloc, but we can't
  71                          * wait for other tasks to complete (and thus free up
  72                          * task structures) without risking deadlock with
  73                          * the caller.  So, we just delay for one second
  74                          * to throttle the allocation rate. If we have tasks
  75                          * complete before one second timeout expires then
  76                          * taskq_ent_free will signal us and we will
  77                          * immediately retry the allocation.
  78                          */
  79                         tq->tq_maxalloc_wait++;
  80                         rv = cv_timedwait(&tq->tq_maxalloc_cv,
  81                             &tq->tq_lock, ddi_get_lbolt() + hz);
  82                         tq->tq_maxalloc_wait--;
  83                         if (rv > 0)
  84                                 goto again;             /* signaled */
  85                 }
  86                 mutex_exit(&tq->tq_lock);
  87
  88                 t = kmem_alloc(sizeof (taskq_ent_t), tqflags);
  89
  90                 mutex_enter(&tq->tq_lock);
  91                 if (t != NULL) {
  92                         /* Make sure we start without any flags */
  93                         t->tqent_flags = 0;
  94                         tq->tq_nalloc++;
  95                 }
  96         }
  97         return (t);
  98 }
  99
 100 static void
 101 task_free(taskq_t *tq, taskq_ent_t *t)
 102 {
 103         if (tq->tq_nalloc <= tq->tq_minalloc) {
 104                 t->tqent_next = tq->tq_freelist;
 105                 tq->tq_freelist = t;
 106         } else {
 107                 tq->tq_nalloc--;
 108                 mutex_exit(&tq->tq_lock);
 109                 kmem_free(t, sizeof (taskq_ent_t));
 110                 mutex_enter(&tq->tq_lock);
 111         }
 112
 113         if (tq->tq_maxalloc_wait)
 114                 cv_signal(&tq->tq_maxalloc_cv);
 115 }
 116
 117 taskqid_t
 118 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 119 {
 120         taskq_ent_t *t;
 121
 122         if (taskq_now) {
 123                 func(arg);
 124                 return (1);
 125         }
 126
 127         mutex_enter(&tq->tq_lock);
 128         ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 129         if ((t = task_alloc(tq, tqflags)) == NULL) {
 130                 mutex_exit(&tq->tq_lock);
 131                 return (0);
 132         }
 133         if (tqflags & TQ_FRONT) {
 134                 t->tqent_next = tq->tq_task.tqent_next;
 135                 t->tqent_prev = &tq->tq_task;
 136         } else {
 137                 t->tqent_next = &tq->tq_task;
 138                 t->tqent_prev = tq->tq_task.tqent_prev;
 139         }
 140         t->tqent_next->tqent_prev = t;
 141         t->tqent_prev->tqent_next = t;
 142         t->tqent_func = func;
 143         t->tqent_arg = arg;
 144         t->tqent_flags = 0;
 145         cv_signal(&tq->tq_dispatch_cv);
 146         mutex_exit(&tq->tq_lock);
 147         return (1);
 148 }
 149
 150 taskqid_t
 151 taskq_dispatch_delay(taskq_t *tq,  task_func_t func, void *arg, uint_t tqflags,
 152     clock_t expire_time)
 153 {
 154         return (0);
 155 }
 156
 157 int
 158 taskq_empty_ent(taskq_ent_t *t)
 159 {
 160         return t->tqent_next == NULL;
 161 }
 162
 163 void
 164 taskq_init_ent(taskq_ent_t *t)
 165 {
 166         t->tqent_next = NULL;
 167         t->tqent_prev = NULL;
 168         t->tqent_func = NULL;
 169         t->tqent_arg = NULL;
 170         t->tqent_flags = 0;
 171 }
 172
 173 void
 174 taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 175     taskq_ent_t *t)
 176 {
 177         ASSERT(func != NULL);
 178         ASSERT(!(tq->tq_flags & TASKQ_DYNAMIC));
 179
 180         /*
 181          * Mark it as a prealloc'd task.  This is important
 182          * to ensure that we don't free it later.
 183          */
 184         t->tqent_flags |= TQENT_FLAG_PREALLOC;
 185         /*
 186          * Enqueue the task to the underlying queue.
 187          */
 188         mutex_enter(&tq->tq_lock);
 189
 190         if (flags & TQ_FRONT) {
 191                 t->tqent_next = tq->tq_task.tqent_next;
 192                 t->tqent_prev = &tq->tq_task;
 193         } else {
 194                 t->tqent_next = &tq->tq_task;
 195                 t->tqent_prev = tq->tq_task.tqent_prev;
 196         }
 197         t->tqent_next->tqent_prev = t;
 198         t->tqent_prev->tqent_next = t;
 199         t->tqent_func = func;
 200         t->tqent_arg = arg;
 201         cv_signal(&tq->tq_dispatch_cv);
 202         mutex_exit(&tq->tq_lock);
 203 }
 204
 205 void
 206 taskq_wait(taskq_t *tq)
 207 {
 208         mutex_enter(&tq->tq_lock);
 209         while (tq->tq_task.tqent_next != &tq->tq_task || tq->tq_active != 0)
 210                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 211         mutex_exit(&tq->tq_lock);
 212 }
 213
 214 static void
 215 taskq_thread(void *arg)
 216 {
 217         taskq_t *tq = arg;
 218         taskq_ent_t *t;
 219         boolean_t prealloc;
 220
 221         mutex_enter(&tq->tq_lock);
 222         while (tq->tq_flags & TASKQ_ACTIVE) {
 223                 if ((t = tq->tq_task.tqent_next) == &tq->tq_task) {
 224                         if (--tq->tq_active == 0)
 225                                 cv_broadcast(&tq->tq_wait_cv);
 226                         cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 227                         tq->tq_active++;
 228                         continue;
 229                 }
 230                 t->tqent_prev->tqent_next = t->tqent_next;
 231                 t->tqent_next->tqent_prev = t->tqent_prev;
 232                 t->tqent_next = NULL;
 233                 t->tqent_prev = NULL;
 234                 prealloc = t->tqent_flags & TQENT_FLAG_PREALLOC;
 235                 mutex_exit(&tq->tq_lock);
 236
 237                 rw_enter(&tq->tq_threadlock, RW_READER);
 238                 t->tqent_func(t->tqent_arg);
 239                 rw_exit(&tq->tq_threadlock);
 240
 241                 mutex_enter(&tq->tq_lock);
 242                 if (!prealloc)
 243                         task_free(tq, t);
 244         }
 245         tq->tq_nthreads--;
 246         cv_broadcast(&tq->tq_wait_cv);
 247         mutex_exit(&tq->tq_lock);
 248         thread_exit();
 249 }
 250
 251 /*ARGSUSED*/
 252 taskq_t *
 253 taskq_create(const char *name, int nthreads, pri_t pri,
 254         int minalloc, int maxalloc, uint_t flags)
 255 {
 256         taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 257         int t;
 258
 259         if (flags & TASKQ_THREADS_CPU_PCT) {
 260                 int pct;
 261                 ASSERT3S(nthreads, >=, 0);
 262                 ASSERT3S(nthreads, <=, 100);
 263                 pct = MIN(nthreads, 100);
 264                 pct = MAX(pct, 0);
 265
 266                 nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
 267                 nthreads = MAX(nthreads, 1);    /* need at least 1 thread */
 268         } else {
 269                 ASSERT3S(nthreads, >=, 1);
 270         }
 271
 272         rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 273         mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 274         cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 275         cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 276         cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
 277         tq->tq_flags = flags | TASKQ_ACTIVE;
 278         tq->tq_active = nthreads;
 279         tq->tq_nthreads = nthreads;
 280         tq->tq_minalloc = minalloc;
 281         tq->tq_maxalloc = maxalloc;
 282         tq->tq_task.tqent_next = &tq->tq_task;
 283         tq->tq_task.tqent_prev = &tq->tq_task;
 284         tq->tq_threadlist = kmem_alloc(nthreads*sizeof(kthread_t *), KM_SLEEP);
 285
 286         if (flags & TASKQ_PREPOPULATE) {
 287                 mutex_enter(&tq->tq_lock);
 288                 while (minalloc-- > 0)
 289                         task_free(tq, task_alloc(tq, KM_SLEEP));
 290                 mutex_exit(&tq->tq_lock);
 291         }
 292
 293         for (t = 0; t < nthreads; t++)
 294                 VERIFY((tq->tq_threadlist[t] = thread_create(NULL, 0,
 295                     taskq_thread, tq, TS_RUN, NULL, 0, 0)) != NULL);
 296
 297         return (tq);
 298 }
 299
 300 void
 301 taskq_destroy(taskq_t *tq)
 302 {
 303         int nthreads = tq->tq_nthreads;
 304
 305         taskq_wait(tq);
 306
 307         mutex_enter(&tq->tq_lock);
 308
 309         tq->tq_flags &= ~TASKQ_ACTIVE;
 310         cv_broadcast(&tq->tq_dispatch_cv);
 311
 312         while (tq->tq_nthreads != 0)
 313                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 314
 315         tq->tq_minalloc = 0;
 316         while (tq->tq_nalloc != 0) {
 317                 ASSERT(tq->tq_freelist != NULL);
 318                 task_free(tq, task_alloc(tq, KM_SLEEP));
 319         }
 320
 321         mutex_exit(&tq->tq_lock);
 322
 323         kmem_free(tq->tq_threadlist, nthreads * sizeof (kthread_t *));
 324
 325         rw_destroy(&tq->tq_threadlock);
 326         mutex_destroy(&tq->tq_lock);
 327         cv_destroy(&tq->tq_dispatch_cv);
 328         cv_destroy(&tq->tq_wait_cv);
 329         cv_destroy(&tq->tq_maxalloc_cv);
 330
 331         kmem_free(tq, sizeof (taskq_t));
 332 }
 333
 334 int
 335 taskq_member(taskq_t *tq, kthread_t *t)
 336 {
 337         int i;
 338
 339         if (taskq_now)
 340                 return (1);
 341
 342         for (i = 0; i < tq->tq_nthreads; i++)
 343                 if (tq->tq_threadlist[i] == t)
 344                         return (1);
 345
 346         return (0);
 347 }
 348
 349 int
 350 taskq_cancel_id(taskq_t *tq, taskqid_t id)
 351 {
 352         return (ENOENT);
 353 }
 354
 355 void
 356 system_taskq_init(void)
 357 {
 358         system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
 359             TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 360 }
 361
 362 void
 363 system_taskq_fini(void)
 364 {
 365         taskq_destroy(system_taskq);
 366         system_taskq = NULL; /* defensive */
 367 }