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         if (new == NULL)
  85                 return new;
  86
  87         new->name = XSTRDUP(MTYPE_WORK_QUEUE_NAME, queue_name);
  88         new->master = m;
  89         SET_FLAG(new->flags, WQ_UNPLUGGED);
  90
  91         STAILQ_INIT(&new->items);
  92
  93         listnode_add(work_queues, new);
  94
  95         new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
  96
  97         /* Default values, can be overriden by caller */
  98         new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
  99         new->spec.yield = THREAD_YIELD_TIME_SLOT;
 100
 101         return new;
 102 }
 103
 104 void work_queue_free(struct work_queue *wq)
 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         return;
 120 }
 121
 122 bool work_queue_is_scheduled(struct work_queue *wq)
 123 {
 124         return (wq->thread != NULL);
 125 }
 126
 127 static int work_queue_schedule(struct work_queue *wq, unsigned int delay)
 128 {
 129         /* if appropriate, schedule work queue thread */
 130         if (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) && (wq->thread == NULL)
 131             && !work_queue_empty(wq)) {
 132                 wq->thread = NULL;
 133                 thread_add_timer_msec(wq->master, work_queue_run, wq, delay,
 134                                       &wq->thread);
 135                 /* set thread yield time, if needed */
 136                 if (wq->thread && wq->spec.yield != THREAD_YIELD_TIME_SLOT)
 137                         thread_set_yield_time(wq->thread, wq->spec.yield);
 138                 return 1;
 139         } else
 140                 return 0;
 141 }
 142
 143 void work_queue_add(struct work_queue *wq, void *data)
 144 {
 145         struct work_queue_item *item;
 146
 147         assert(wq);
 148
 149         if (!(item = work_queue_item_new(wq))) {
 150                 zlog_err("%s: unable to get new queue item", __func__);
 151                 return;
 152         }
 153
 154         item->data = data;
 155         work_queue_item_enqueue(wq, item);
 156
 157         work_queue_schedule(wq, wq->spec.hold);
 158
 159         return;
 160 }
 161
 162 static void work_queue_item_requeue(struct work_queue *wq,
 163                                     struct work_queue_item *item)
 164 {
 165         work_queue_item_dequeue(wq, item);
 166
 167         /* attach to end of list */
 168         work_queue_item_enqueue(wq, item);
 169 }
 170
 171 DEFUN (show_work_queues,
 172        show_work_queues_cmd,
 173        "show work-queues",
 174        SHOW_STR
 175        "Work Queue information\n")
 176 {
 177         struct listnode *node;
 178         struct work_queue *wq;
 179
 180         vty_out(vty, "%c %8s %5s %8s %8s %21s\n", ' ', "List", "(ms) ",
 181                 "Q. Runs", "Yields", "Cycle Counts   ");
 182         vty_out(vty, "%c %8s %5s %8s %8s %7s %6s %8s %6s %s\n", 'P', "Items",
 183                 "Hold", "Total", "Total", "Best", "Gran.", "Total", "Avg.",
 184                 "Name");
 185
 186         for (ALL_LIST_ELEMENTS_RO(work_queues, node, wq)) {
 187                 vty_out(vty, "%c %8d %5d %8ld %8ld %7d %6d %8ld %6u %s\n",
 188                         (CHECK_FLAG(wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
 189                         work_queue_item_count(wq), wq->spec.hold, wq->runs,
 190                         wq->yields, wq->cycles.best, wq->cycles.granularity,
 191                         wq->cycles.total,
 192                         (wq->runs) ? (unsigned int)(wq->cycles.total / wq->runs)
 193                                    : 0,
 194                         wq->name);
 195         }
 196
 197         return CMD_SUCCESS;
 198 }
 199
 200 void workqueue_cmd_init(void)
 201 {
 202         install_element(VIEW_NODE, &show_work_queues_cmd);
 203 }
 204
 205 /* 'plug' a queue: Stop it from being scheduled,
 206  * ie: prevent the queue from draining.
 207  */
 208 void work_queue_plug(struct work_queue *wq)
 209 {
 210         if (wq->thread)
 211                 thread_cancel(wq->thread);
 212
 213         wq->thread = NULL;
 214
 215         UNSET_FLAG(wq->flags, WQ_UNPLUGGED);
 216 }
 217
 218 /* unplug queue, schedule it again, if appropriate
 219  * Ie: Allow the queue to be drained again
 220  */
 221 void work_queue_unplug(struct work_queue *wq)
 222 {
 223         SET_FLAG(wq->flags, WQ_UNPLUGGED);
 224
 225         /* if thread isnt already waiting, add one */
 226         work_queue_schedule(wq, wq->spec.hold);
 227 }
 228
 229 /* timer thread to process a work queue
 230  * will reschedule itself if required,
 231  * otherwise work_queue_item_add
 232  */
 233 int work_queue_run(struct thread *thread)
 234 {
 235         struct work_queue *wq;
 236         struct work_queue_item *item, *titem;
 237         wq_item_status ret;
 238         unsigned int cycles = 0;
 239         char yielded = 0;
 240
 241         wq = THREAD_ARG(thread);
 242         wq->thread = NULL;
 243
 244         assert(wq);
 245
 246         /* calculate cycle granularity:
 247          * list iteration == 1 run
 248          * listnode processing == 1 cycle
 249          * granularity == # cycles between checks whether we should yield.
 250          *
 251          * granularity should be > 0, and can increase slowly after each run to
 252          * provide some hysteris, but not past cycles.best or 2*cycles.
 253          *
 254          * Best: starts low, can only increase
 255          *
 256          * Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
 257          *              if we run to end of time slot, can increase otherwise
 258          *              by a small factor.
 259          *
 260          * We could use just the average and save some work, however we want to
 261          * be
 262          * able to adjust quickly to CPU pressure. Average wont shift much if
 263          * daemon has been running a long time.
 264          */
 265         if (wq->cycles.granularity == 0)
 266                 wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
 267
 268         STAILQ_FOREACH_SAFE (item, &wq->items, wq, titem) {
 269                 assert(item && item->data);
 270
 271                 /* dont run items which are past their allowed retries */
 272                 if (item->ran > wq->spec.max_retries) {
 273                         /* run error handler, if any */
 274                         if (wq->spec.errorfunc)
 275                                 wq->spec.errorfunc(wq, item->data);
 276                         work_queue_item_remove(wq, item);
 277                         continue;
 278                 }
 279
 280                 /* run and take care of items that want to be retried
 281                  * immediately */
 282                 do {
 283                         ret = wq->spec.workfunc(wq, item->data);
 284                         item->ran++;
 285                 } while ((ret == WQ_RETRY_NOW)
 286                          && (item->ran < wq->spec.max_retries));
 287
 288                 switch (ret) {
 289                 case WQ_QUEUE_BLOCKED: {
 290                         /* decrement item->ran again, cause this isn't an item
 291                          * specific error, and fall through to WQ_RETRY_LATER
 292                          */
 293                         item->ran--;
 294                 }
 295                 case WQ_RETRY_LATER: {
 296                         goto stats;
 297                 }
 298                 case WQ_REQUEUE: {
 299                         item->ran--;
 300                         work_queue_item_requeue(wq, item);
 301                         /* If a single node is being used with a meta-queue
 302                          * (e.g., zebra),
 303                          * update the next node as we don't want to exit the
 304                          * thread and
 305                          * reschedule it after every node. By definition,
 306                          * WQ_REQUEUE is
 307                          * meant to continue the processing; the yield logic
 308                          * will kick in
 309                          * to terminate the thread when time has exceeded.
 310                          */
 311                         if (titem == NULL)
 312                                 titem = item;
 313                         break;
 314                 }
 315                 case WQ_RETRY_NOW:
 316                 /* a RETRY_NOW that gets here has exceeded max_tries, same as
 317                  * ERROR */
 318                 case WQ_ERROR: {
 319                         if (wq->spec.errorfunc)
 320                                 wq->spec.errorfunc(wq, item);
 321                 }
 322                 /* fallthru */
 323                 case WQ_SUCCESS:
 324                 default: {
 325                         work_queue_item_remove(wq, item);
 326                         break;
 327                 }
 328                 }
 329
 330                 /* completed cycle */
 331                 cycles++;
 332
 333                 /* test if we should yield */
 334                 if (!(cycles % wq->cycles.granularity)
 335                     && thread_should_yield(thread)) {
 336                         yielded = 1;
 337                         goto stats;
 338                 }
 339         }
 340
 341 stats:
 342
 343 #define WQ_HYSTERESIS_FACTOR 4
 344
 345         /* we yielded, check whether granularity should be reduced */
 346         if (yielded && (cycles < wq->cycles.granularity)) {
 347                 wq->cycles.granularity =
 348                         ((cycles > 0) ? cycles : WORK_QUEUE_MIN_GRANULARITY);
 349         }
 350         /* otherwise, should granularity increase? */
 351         else if (cycles >= (wq->cycles.granularity)) {
 352                 if (cycles > wq->cycles.best)
 353                         wq->cycles.best = cycles;
 354
 355                 /* along with yielded check, provides hysteresis for granularity
 356                  */
 357                 if (cycles > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR
 358                               * WQ_HYSTERESIS_FACTOR))
 359                         wq->cycles.granularity *=
 360                                 WQ_HYSTERESIS_FACTOR; /* quick ramp-up */
 361                 else if (cycles
 362                          > (wq->cycles.granularity * WQ_HYSTERESIS_FACTOR))
 363                         wq->cycles.granularity += WQ_HYSTERESIS_FACTOR;
 364         }
 365 #undef WQ_HYSTERIS_FACTOR
 366
 367         wq->runs++;
 368         wq->cycles.total += cycles;
 369         if (yielded)
 370                 wq->yields++;
 371
 372 #if 0
 373   printf ("%s: cycles %d, new: best %d, worst %d\n",
 374             __func__, cycles, wq->cycles.best, wq->cycles.granularity);
 375 #endif
 376
 377         /* Is the queue done yet? If it is, call the completion callback. */
 378         if (!work_queue_empty(wq))
 379                 work_queue_schedule(wq, 0);
 380         else if (wq->spec.completion_func)
 381                 wq->spec.completion_func(wq);
 382
 383         return 0;
 384 }