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 #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         kthread_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         task_t          *tq_freelist;
  55         task_t          tq_task;
  56 };
  57
  58 static task_t *
  59 task_alloc(taskq_t *tq, int tqflags)
  60 {
  61         task_t *t;
  62         int rv;
  63
  64 again:  if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
  65                 tq->tq_freelist = t->task_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                         rv = cv_timedwait(&tq->tq_maxalloc_cv,
  83                             &tq->tq_lock, ddi_get_lbolt() + hz);
  84                         tq->tq_maxalloc_wait--;
  85                         if (rv > 0)
  86                                 goto again;             /* signaled */
  87                 }
  88                 mutex_exit(&tq->tq_lock);
  89
  90                 t = kmem_alloc(sizeof (task_t), tqflags);
  91
  92                 mutex_enter(&tq->tq_lock);
  93                 if (t != NULL)
  94                         tq->tq_nalloc++;
  95         }
  96         return (t);
  97 }
  98
  99 static void
 100 task_free(taskq_t *tq, task_t *t)
 101 {
 102         if (tq->tq_nalloc <= tq->tq_minalloc) {
 103                 t->task_next = tq->tq_freelist;
 104                 tq->tq_freelist = t;
 105         } else {
 106                 tq->tq_nalloc--;
 107                 mutex_exit(&tq->tq_lock);
 108                 kmem_free(t, sizeof (task_t));
 109                 mutex_enter(&tq->tq_lock);
 110         }
 111
 112         if (tq->tq_maxalloc_wait)
 113                 cv_signal(&tq->tq_maxalloc_cv);
 114 }
 115
 116 taskqid_t
 117 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 118 {
 119         task_t *t;
 120
 121         if (taskq_now) {
 122                 func(arg);
 123                 return (1);
 124         }
 125
 126         mutex_enter(&tq->tq_lock);
 127         ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 128         if ((t = task_alloc(tq, tqflags)) == NULL) {
 129                 mutex_exit(&tq->tq_lock);
 130                 return (0);
 131         }
 132         if (tqflags & TQ_FRONT) {
 133                 t->task_next = tq->tq_task.task_next;
 134                 t->task_prev = &tq->tq_task;
 135         } else {
 136                 t->task_next = &tq->tq_task;
 137                 t->task_prev = tq->tq_task.task_prev;
 138         }
 139         t->task_next->task_prev = t;
 140         t->task_prev->task_next = t;
 141         t->task_func = func;
 142         t->task_arg = arg;
 143         cv_signal(&tq->tq_dispatch_cv);
 144         mutex_exit(&tq->tq_lock);
 145         return (1);
 146 }
 147
 148 void
 149 taskq_wait(taskq_t *tq)
 150 {
 151         mutex_enter(&tq->tq_lock);
 152         while (tq->tq_task.task_next != &tq->tq_task || tq->tq_active != 0)
 153                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 154         mutex_exit(&tq->tq_lock);
 155 }
 156
 157 static void
 158 taskq_thread(void *arg)
 159 {
 160         taskq_t *tq = arg;
 161         task_t *t;
 162
 163         mutex_enter(&tq->tq_lock);
 164         while (tq->tq_flags & TASKQ_ACTIVE) {
 165                 if ((t = tq->tq_task.task_next) == &tq->tq_task) {
 166                         if (--tq->tq_active == 0)
 167                                 cv_broadcast(&tq->tq_wait_cv);
 168                         cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 169                         tq->tq_active++;
 170                         continue;
 171                 }
 172                 t->task_prev->task_next = t->task_next;
 173                 t->task_next->task_prev = t->task_prev;
 174                 mutex_exit(&tq->tq_lock);
 175
 176                 rw_enter(&tq->tq_threadlock, RW_READER);
 177                 t->task_func(t->task_arg);
 178                 rw_exit(&tq->tq_threadlock);
 179
 180                 mutex_enter(&tq->tq_lock);
 181                 task_free(tq, t);
 182         }
 183         tq->tq_nthreads--;
 184         cv_broadcast(&tq->tq_wait_cv);
 185         mutex_exit(&tq->tq_lock);
 186         thread_exit();
 187 }
 188
 189 /*ARGSUSED*/
 190 taskq_t *
 191 taskq_create(const char *name, int nthreads, pri_t pri,
 192         int minalloc, int maxalloc, uint_t flags)
 193 {
 194         taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 195         int t;
 196
 197         if (flags & TASKQ_THREADS_CPU_PCT) {
 198                 int pct;
 199                 ASSERT3S(nthreads, >=, 0);
 200                 ASSERT3S(nthreads, <=, 100);
 201                 pct = MIN(nthreads, 100);
 202                 pct = MAX(pct, 0);
 203
 204                 nthreads = (sysconf(_SC_NPROCESSORS_ONLN) * pct) / 100;
 205                 nthreads = MAX(nthreads, 1);    /* need at least 1 thread */
 206         } else {
 207                 ASSERT3S(nthreads, >=, 1);
 208         }
 209
 210         rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 211         mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 212         cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 213         cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 214         cv_init(&tq->tq_maxalloc_cv, NULL, CV_DEFAULT, NULL);
 215         tq->tq_flags = flags | TASKQ_ACTIVE;
 216         tq->tq_active = nthreads;
 217         tq->tq_nthreads = nthreads;
 218         tq->tq_minalloc = minalloc;
 219         tq->tq_maxalloc = maxalloc;
 220         tq->tq_task.task_next = &tq->tq_task;
 221         tq->tq_task.task_prev = &tq->tq_task;
 222         tq->tq_threadlist = kmem_alloc(nthreads*sizeof(kthread_t *), KM_SLEEP);
 223
 224         if (flags & TASKQ_PREPOPULATE) {
 225                 mutex_enter(&tq->tq_lock);
 226                 while (minalloc-- > 0)
 227                         task_free(tq, task_alloc(tq, KM_SLEEP));
 228                 mutex_exit(&tq->tq_lock);
 229         }
 230
 231         for (t = 0; t < nthreads; t++)
 232                 VERIFY((tq->tq_threadlist[t] = thread_create(NULL, 0,
 233                     taskq_thread, tq, TS_RUN, NULL, 0, 0)) != NULL);
 234
 235         return (tq);
 236 }
 237
 238 void
 239 taskq_destroy(taskq_t *tq)
 240 {
 241         int nthreads = tq->tq_nthreads;
 242
 243         taskq_wait(tq);
 244
 245         mutex_enter(&tq->tq_lock);
 246
 247         tq->tq_flags &= ~TASKQ_ACTIVE;
 248         cv_broadcast(&tq->tq_dispatch_cv);
 249
 250         while (tq->tq_nthreads != 0)
 251                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 252
 253         tq->tq_minalloc = 0;
 254         while (tq->tq_nalloc != 0) {
 255                 ASSERT(tq->tq_freelist != NULL);
 256                 task_free(tq, task_alloc(tq, KM_SLEEP));
 257         }
 258
 259         mutex_exit(&tq->tq_lock);
 260
 261         kmem_free(tq->tq_threadlist, nthreads * sizeof (kthread_t *));
 262
 263         rw_destroy(&tq->tq_threadlock);
 264         mutex_destroy(&tq->tq_lock);
 265         cv_destroy(&tq->tq_dispatch_cv);
 266         cv_destroy(&tq->tq_wait_cv);
 267         cv_destroy(&tq->tq_maxalloc_cv);
 268
 269         kmem_free(tq, sizeof (taskq_t));
 270 }
 271
 272 int
 273 taskq_member(taskq_t *tq, kthread_t *t)
 274 {
 275         int i;
 276
 277         if (taskq_now)
 278                 return (1);
 279
 280         for (i = 0; i < tq->tq_nthreads; i++)
 281                 if (tq->tq_threadlist[i] == t)
 282                         return (1);
 283
 284         return (0);
 285 }
 286
 287 void
 288 system_taskq_init(void)
 289 {
 290         system_taskq = taskq_create("system_taskq", 64, minclsyspri, 4, 512,
 291             TASKQ_DYNAMIC | TASKQ_PREPOPULATE);
 292 }
 293
 294 void
 295 system_taskq_fini(void)
 296 {
 297         taskq_destroy(system_taskq);
 298         system_taskq = NULL; /* defensive */
 299 }