lib/workqueue.c

   1 /*
   2  * Quagga Work Queue Support.
   3  *
   4  * Copyright (C) 2005 Sun Microsystems, Inc.
   5  *
   6  * This file is part of GNU Zebra.
   7  *
   8  * Quagga is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2, or (at your option) any
  11  * later version.
  12  *
  13  * Quagga is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; see the file COPYING; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <zebra.h>
  24 #include "thread.h"
  25 #include "memory.h"
  26 #include "workqueue.h"
  27 #include "linklist.h"
  28 #include "command.h"
  29 #include "log.h"
  30
  31 DEFINE_MTYPE(LIB, WORK_QUEUE, "Work queue")
  32 DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_ITEM, "Work queue item")
  33 DEFINE_MTYPE_STATIC(LIB, WORK_QUEUE_NAME, "Work queue name string")
  34
  35 /* master list of work_queues */
  36 static struct list _work_queues;
  37 /* pointer primarily to avoid an otherwise harmless warning on
  38  * ALL_LIST_ELEMENTS_RO
  39  */
  40 static struct list *work_queues = &_work_queues;
  41
  42 #define WORK_QUEUE_MIN_GRANULARITY 1
  43
  44 static struct work_queue_item *work_queue_item_new(struct work_queue *wq)
  45 {
  46         struct work_queue_item *item;
  47         assert(wq);
  48
  49         item = XCALLOC(MTYPE_WORK_QUEUE_ITEM, sizeof(struct work_queue_item));
  50
  51         return item;
  52 }
  53
  54 static void work_queue_item_free(struct work_queue_item *item)
  55 {
  56         XFREE(MTYPE_WORK_QUEUE_ITEM, item);
  57         return;
  58 }
  59
  60 static void work_queue_item_remove(struct work_queue *wq,
  61                                    struct work_queue_item *item)
  62 {
  63         assert(item && item->data);
  64
  65         /* call private data deletion callback if needed */
  66         if (wq->spec.del_item_data)
  67                 wq->spec.del_item_data(wq, item->data);
  68
  69         work_queue_item_dequeue(wq, item);
  70
  71         work_queue_item_free(item);
  72
  73         return;
  74 }
  75
  76 /* create new work queue */
  77 struct work_queue *work_queue_new(struct thread_master *m,
  78                                   const char *queue_name)
  79 {
  80         struct work_queue *new;
  81
  82         new = XCALLOC(MTYPE_WORK_QUEUE, sizeof(struct work_queue));
  83
  84         new->name = XSTRDUP(MTYPE_WORK_QUEUE_NAME, queue_name);
  85         new->master = m;
  86         SET_FLAG(new->flags, WQ_UNPLUGGED);
  87
  88         STAILQ_INIT(&new->items);
  89
  90         listnode_add(work_queues, new);
  91
  92         new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
  93
  94         /* Default values, can be overridden by caller */
  95         new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
  96         new->spec.yield = THREAD_YIELD_TIME_SLOT;
  97         new->spec.retry = WORK_QUEUE_DEFAULT_RETRY;
  98
  99         return new;
 100 }
 101
 102 void work_queue_free_and_null(struct work_queue **wqp)
 103 {
 104         struct work_queue *wq = *wqp;
 105
 106         if (wq->thread != NULL)
 107                 thread_cancel(wq->thread);
 108
 109         while (!work_queue_empty(wq)) {
 110                 struct work_queue_item *item = work_queue_last_item(wq);
 111
 112                 work_queue_item_remove(wq, item);
 113         }
 114
 115         listnode_delete(work_queues, wq);
 116
 117         XFREE(MTYPE_WORK_QUEUE_NAME, wq->name);
 118         XFREE(MTYPE_WORK_QUEUE, wq);
 119
 120         *wqp = NULL;
 121 }
 122
 123 bool work_queue_is_scheduled(struct work_queue *wq)
 124 {
 125         return (wq->thread != NULL);
 126 }
 127
 128 static int work_queue_schedule(struct work_queue *wq, unsigned int delay)
 129 {
 130         /* if appropriate, schedule work queue thread */
 131         if (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) && (wq->thread == NULL)
 132             && !work_queue_empty(wq)) {
 133                 wq->thread = NULL;
 134
 135                 /* Schedule timer if there's a delay, otherwise just schedule
 136                  * as an 'event'
 137                  */
 138                 if (delay > 0)
 139                         thread_add_timer_msec(wq->master, work_queue_run, wq,
 140                                               delay, &wq->thread);
 141                 else
 142                         thread_add_event(wq->master, work_queue_run, wq, 0,
 143                                          &wq->thread);
 144
 145                 /* set thread yield time, if needed */
 146                 if (wq->thread && wq->spec.yield != THREAD_YIELD_TIME_SLOT)
 147                         thread_set_yield_time(wq->thread, wq->spec.yield);
 148                 return 1;
 149         } else
 150                 return 0;
 151 }
 152
 153 void work_queue_add(struct work_queue *wq, void *data)
 154 {
 155         struct work_queue_item *item;
 156
 157         assert(wq);
 158
 159         item = work_queue_item_new(wq);
 160
 161         item->data = data;
 162         work_queue_item_enqueue(wq, item);
 163
 164         work_queue_schedule(wq, wq->spec.hold);
 165
 166         return;
 167 }
 168
 169 static void work_queue_item_requeue(struct work_queue *wq,
 170                                     struct work_queue_item *item)
 171 {
 172         work_queue_item_dequeue(wq, item);
 173
 174         /* attach to end of list */
 175         work_queue_item_enqueue(wq, item);
 176 }
 177
 178 DEFUN (show_work_queues,
 179        show_work_queues_cmd,
 180        "show work-queues",
 181        SHOW_STR
 182        "Work Queue information\n")
 183 {
 184         struct listnode *node;
 185         struct work_queue *wq;
 186
 187         vty_out(vty, "%c %8s %5s %8s %8s %21s\n", ' ', "List", "(ms) ",
 188                 "Q. Runs", "Yields", "Cycle Counts   ");
 189         vty_out(vty, "%c %8s %5s %8s %8s %7s %6s %8s %6s %s\n", 'P', "Items",
 190                 "Hold", "Total", "Total", "Best", "Gran.", "Total", "Avg.",
 191                 "Name");
 192
 193         for (ALL_LIST_ELEMENTS_RO(work_queues, node, wq)) {
 194                 vty_out(vty, "%c %8d %5d %8ld %8ld %7d %6d %8ld %6u %s\n",
 195                         (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
 196                         work_queue_item_count(wq), wq->spec.hold, wq->runs,
 197                         wq->yields, wq->cycles.best, wq->cycles.granularity,
 198                         wq->cycles.total,
 199                         (wq->runs) ? (unsigned int)(wq->cycles.total / wq->runs)
 200                                    : 0,
 201                         wq->name);
 202         }
 203
 204         return CMD_SUCCESS;
 205 }
 206
 207 void workqueue_cmd_init(void)
 208 {
 209         install_element(VIEW_NODE, &show_work_queues_cmd);
 210 }
 211
 212 /* 'plug' a queue: Stop it from being scheduled,
 213  * ie: prevent the queue from draining.
 214  */
 215 void work_queue_plug(struct work_queue *wq)
 216 {
 217         if (wq->thread)
 218                 thread_cancel(wq->thread);
 219
 220         wq->thread = NULL;
 221
 222         UNSET_FLAG(wq->flags, WQ_UNPLUGGED);
 223 }
 224
 225 /* unplug queue, schedule it again, if appropriate
 226  * Ie: Allow the queue to be drained again
 227  */
 228 void work_queue_unplug(struct work_queue *wq)
 229 {
 230         SET_FLAG(wq->flags, WQ_UNPLUGGED);
 231
 232         /* if thread isnt already waiting, add one */
 233         work_queue_schedule(wq, wq->spec.hold);
 234 }
 235
 236 /* timer thread to process a work queue
 237  * will reschedule itself if required,
 238  * otherwise work_queue_item_add
 239  */
 240 int work_queue_run(struct thread *thread)
 241 {
 242         struct work_queue *wq;
 243         struct work_queue_item *item, *titem;
 244         wq_item_status ret = WQ_SUCCESS;
 245         unsigned int cycles = 0;
 246         char yielded = 0;
 247
 248         wq = THREAD_ARG(thread);
 249
 250         assert(wq);
 251
 252         wq->thread = NULL;
 253
 254         /* calculate cycle granularity:
 255          * list iteration == 1 run
 256          * listnode processing == 1 cycle
 257          * granularity == # cycles between checks whether we should yield.
 258          *
 259          * granularity should be > 0, and can increase slowly after each run to
 260          * provide some hysteris, but not past cycles.best or 2*cycles.
 261          *
 262          * Best: starts low, can only increase
 263          *
 264          * Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
 265          *              if we run to end of time slot, can increase otherwise
 266          *              by a small factor.
 267          *
 268          * We could use just the average and save some work, however we want to
 269          * be
 270          * able to adjust quickly to CPU pressure. Average wont shift much if
 271          * daemon has been running a long time.
 272          */
 273         if (wq->cycles.granularity == 0)
 274                 wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
 275
 276         STAILQ_FOREACH_SAFE (item, &wq->items, wq, titem) {
 277                 assert(item->data);
 278
 279                 /* dont run items which are past their allowed retries */
 280                 if (item->ran > wq->spec.max_retries) {
 281                         /* run error handler, if any */
 282                         if (wq->spec.errorfunc)
 283                                 wq->spec.errorfunc(wq, item);
 284                         work_queue_item_remove(wq, item);
 285                         continue;
 286                 }
 287
 288                 /* run and take care of items that want to be retried
 289                  * immediately */
 290                 do {
 291                         ret = wq->spec.workfunc(wq, item->data);
 292                         item->ran++;
 293                 } while ((ret == WQ_RETRY_NOW)
 294                          && (item->ran < wq->spec.max_retries));
 295
 296                 switch (ret) {
 297                 case WQ_QUEUE_BLOCKED: {
 298                         /* decrement item->ran again, cause this isn't an item
 299                          * specific error, and fall through to WQ_RETRY_LATER
 300                          */
 301                         item->ran--;
 302                 }
 303                 case WQ_RETRY_LATER: {
 304                         goto stats;
 305                 }
 306                 case WQ_REQUEUE: {
 307                         item->ran--;
 308                         work_queue_item_requeue(wq, item);
 309                         /* If a single node is being used with a meta-queue
 310                          * (e.g., zebra),
 311                          * update the next node as we don't want to exit the
 312                          * thread and
 313                          * reschedule it after every node. By definition,
 314                          * WQ_REQUEUE is
 315                          * meant to continue the processing; the yield logic
 316                          * will kick in
 317                          * to terminate the thread when time has exceeded.
 318                          */
 319                         if (titem == NULL)
 320                                 titem = item;
 321                         break;
 322                 }
 323                 case WQ_RETRY_NOW:
 324                 /* a RETRY_NOW that gets here has exceeded max_tries, same as
 325                  * ERROR */
 326                 case WQ_ERROR: {
 327                         if (wq->spec.errorfunc)
 328                                 wq->spec.errorfunc(wq, item);
 329                 }
 330                 /* fallthru */
 331                 case WQ_SUCCESS:
 332                 default: {
 333                         work_queue_item_remove(wq, item);
 334                         break;
 335                 }
 336                 }
 337
 338                 /* completed cycle */
 339                 cycles++;
 340
 341                 /* test if we should yield */
 342                 if (!(cycles % wq->cycles.granularity)
 343                     && thread_should_yield(thread)) {
 344                         yielded = 1;
 345                         goto stats;
 346                 }
 347         }
 348
 349 stats:
 350
 351 #define WQ_HYSTERESIS_FACTOR 4
 352
 353         /* we yielded, check whether granularity should be reduced */
 354         if (yielded && (cycles < wq->cycles.granularity)) {
 355                 wq->cycles.granularity =
 356                         ((cycles > 0) ? cycles : WORK_QUEUE_MIN_GRANULARITY);
 357         }
 358         /* otherwise, should granularity increase? */
 359         else if (cycles >= (wq->cycles.granularity)) {
 360                 if (cycles > wq->cycles.best)
 361                         wq->cycles.best = cycles;
 362
 363                 /* along with yielded check, provides hysteresis for granularity
 364                  */
 365                 if (cycles > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR
 366                               * WQ_HYSTERESIS_FACTOR))
 367                         wq->cycles.granularity *=
 368                                 WQ_HYSTERESIS_FACTOR; /* quick ramp-up */
 369                 else if (cycles
 370                          > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR))
 371                         wq->cycles.granularity += WQ_HYSTERESIS_FACTOR;
 372         }
 373 #undef WQ_HYSTERIS_FACTOR
 374
 375         wq->runs++;
 376         wq->cycles.total += cycles;
 377         if (yielded)
 378                 wq->yields++;
 379
 380 #if 0
 381   printf ("%s: cycles %d, new: best %d, worst %d\n",
 382             __func__, cycles, wq->cycles.best, wq->cycles.granularity);
 383 #endif
 384
 385         /* Is the queue done yet? If it is, call the completion callback. */
 386         if (!work_queue_empty(wq)) {
 387                 if (ret == WQ_RETRY_LATER ||
 388                     ret == WQ_QUEUE_BLOCKED)
 389                         work_queue_schedule(wq, wq->spec.retry);
 390                 else
 391                         work_queue_schedule(wq, 0);
 392
 393         } else if (wq->spec.completion_func)
 394                 wq->spec.completion_func(wq);
 395
 396         return 0;
 397 }