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
  19  * along with Quagga; see the file COPYING.  If not, write to the Free
  20  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  21  * 02111-1307, USA.
  22  */
  23
  24 #include <lib/zebra.h>
  25 #include "thread.h"
  26 #include "memory.h"
  27 #include "workqueue.h"
  28 #include "linklist.h"
  29 #include "command.h"
  30 #include "log.h"
  31
  32 /* master list of work_queues */
  33 static struct list work_queues;
  34
  35 #define WORK_QUEUE_MIN_GRANULARITY 1
  36
  37 static struct work_queue_item *
  38 work_queue_item_new (struct work_queue *wq)
  39 {
  40   struct work_queue_item *item;
  41   assert (wq);
  42
  43   item = XCALLOC (MTYPE_WORK_QUEUE_ITEM,
  44                   sizeof (struct work_queue_item));
  45
  46   return item;
  47 }
  48
  49 static void
  50 work_queue_item_free (struct work_queue_item *item)
  51 {
  52   XFREE (MTYPE_WORK_QUEUE_ITEM, item);
  53   return;
  54 }
  55
  56 /* create new work queue */
  57 struct work_queue *
  58 work_queue_new (struct thread_master *m, const char *queue_name)
  59 {
  60   struct work_queue *new;
  61
  62   new = XCALLOC (MTYPE_WORK_QUEUE, sizeof (struct work_queue));
  63
  64   if (new == NULL)
  65     return new;
  66
  67   new->name = XSTRDUP (MTYPE_WORK_QUEUE_NAME, queue_name);
  68   new->master = m;
  69   SET_FLAG (new->flags, WQ_UNPLUGGED);
  70
  71   if ( (new->items = list_new ()) == NULL)
  72     {
  73       XFREE (MTYPE_WORK_QUEUE_NAME, new->name);
  74       XFREE (MTYPE_WORK_QUEUE, new);
  75
  76       return NULL;
  77     }
  78
  79   new->items->del = (void (*)(void *)) work_queue_item_free;
  80
  81   listnode_add (&work_queues, new);
  82
  83   new->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
  84
  85   /* Default values, can be overriden by caller */
  86   new->spec.hold = WORK_QUEUE_DEFAULT_HOLD;
  87
  88   return new;
  89 }
  90
  91 void
  92 work_queue_free (struct work_queue *wq)
  93 {
  94   /* list_delete frees items via callback */
  95   list_delete (wq->items);
  96   listnode_delete (&work_queues, wq);
  97
  98   XFREE (MTYPE_WORK_QUEUE_NAME, wq->name);
  99   XFREE (MTYPE_WORK_QUEUE, wq);
 100   return;
 101 }
 102
 103 static inline int
 104 work_queue_schedule (struct work_queue *wq, unsigned int delay)
 105 {
 106   /* if appropriate, schedule work queue thread */
 107   if ( CHECK_FLAG (wq->flags, WQ_UNPLUGGED)
 108        && (wq->thread == NULL)
 109        && (listcount (wq->items) > 0) )
 110     {
 111       wq->thread = thread_add_background (wq->master, work_queue_run,
 112                                           wq, delay);
 113       return 1;
 114     }
 115   else
 116     return 0;
 117 }
 118
 119 void
 120 work_queue_add (struct work_queue *wq, void *data)
 121 {
 122   struct work_queue_item *item;
 123
 124   assert (wq);
 125
 126   if (!(item = work_queue_item_new (wq)))
 127     {
 128       zlog_err ("%s: unable to get new queue item", __func__);
 129       return;
 130     }
 131
 132   item->data = data;
 133   listnode_add (wq->items, item);
 134
 135   work_queue_schedule (wq, wq->spec.hold);
 136
 137   return;
 138 }
 139
 140 static void
 141 work_queue_item_remove (struct work_queue *wq, struct listnode *ln)
 142 {
 143   struct work_queue_item *item = listgetdata (ln);
 144
 145   assert (item && item->data);
 146
 147   /* call private data deletion callback if needed */
 148   if (wq->spec.del_item_data)
 149     wq->spec.del_item_data (wq, item->data);
 150
 151   list_delete_node (wq->items, ln);
 152   work_queue_item_free (item);
 153
 154   return;
 155 }
 156
 157 static void
 158 work_queue_item_requeue (struct work_queue *wq, struct listnode *ln)
 159 {
 160   LISTNODE_DETACH (wq->items, ln);
 161   LISTNODE_ATTACH (wq->items, ln); /* attach to end of list */
 162 }
 163
 164 DEFUN(show_work_queues,
 165       show_work_queues_cmd,
 166       "show work-queues",
 167       SHOW_STR
 168       "Work Queue information\n")
 169 {
 170   struct listnode *node;
 171   struct work_queue *wq;
 172
 173   vty_out (vty,
 174            "%c %8s %5s %8s %21s%s",
 175            ' ', "List","(ms) ","Q. Runs","Cycle Counts   ",
 176            VTY_NEWLINE);
 177   vty_out (vty,
 178            "%c %8s %5s %8s %7s %6s %6s %s%s",
 179            'P',
 180            "Items",
 181            "Hold",
 182            "Total",
 183            "Best","Gran.","Avg.",
 184            "Name",
 185            VTY_NEWLINE);
 186
 187   for (ALL_LIST_ELEMENTS_RO ((&work_queues), node, wq))
 188     {
 189       vty_out (vty,"%c %8d %5d %8ld %7d %6d %6u %s%s",
 190                (CHECK_FLAG (wq->flags, WQ_UNPLUGGED) ? ' ' : 'P'),
 191                listcount (wq->items),
 192                wq->spec.hold,
 193                wq->runs,
 194                wq->cycles.best, wq->cycles.granularity,
 195                  (wq->runs) ?
 196                    (unsigned int) (wq->cycles.total / wq->runs) : 0,
 197                wq->name,
 198                VTY_NEWLINE);
 199     }
 200
 201   return CMD_SUCCESS;
 202 }
 203
 204 /* 'plug' a queue: Stop it from being scheduled,
 205  * ie: prevent the queue from draining.
 206  */
 207 void
 208 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
 222 work_queue_unplug (struct work_queue *wq)
 223 {
 224   SET_FLAG (wq->flags, WQ_UNPLUGGED);
 225
 226   /* if thread isnt already waiting, add one */
 227   work_queue_schedule (wq, wq->spec.hold);
 228 }
 229
 230 /* timer thread to process a work queue
 231  * will reschedule itself if required,
 232  * otherwise work_queue_item_add
 233  */
 234 int
 235 work_queue_run (struct thread *thread)
 236 {
 237   struct work_queue *wq;
 238   struct work_queue_item *item;
 239   wq_item_status ret;
 240   unsigned int cycles = 0;
 241   struct listnode *node, *nnode;
 242   char yielded = 0;
 243
 244   wq = THREAD_ARG (thread);
 245   wq->thread = NULL;
 246
 247   assert (wq && wq->items);
 248
 249   /* calculate cycle granularity:
 250    * list iteration == 1 cycle
 251    * granularity == # cycles between checks whether we should yield.
 252    *
 253    * granularity should be > 0, and can increase slowly after each run to
 254    * provide some hysteris, but not past cycles.best or 2*cycles.
 255    *
 256    * Best: starts low, can only increase
 257    *
 258    * Granularity: starts at WORK_QUEUE_MIN_GRANULARITY, can be decreased
 259    *              if we run to end of time slot, can increase otherwise
 260    *              by a small factor.
 261    *
 262    * We could use just the average and save some work, however we want to be
 263    * able to adjust quickly to CPU pressure. Average wont shift much if
 264    * daemon has been running a long time.
 265    */
 266    if (wq->cycles.granularity == 0)
 267      wq->cycles.granularity = WORK_QUEUE_MIN_GRANULARITY;
 268
 269   for (ALL_LIST_ELEMENTS (wq->items, node, nnode, item))
 270   {
 271     assert (item && item->data);
 272
 273     /* dont run items which are past their allowed retries */
 274     if (item->ran > wq->spec.max_retries)
 275       {
 276         /* run error handler, if any */
 277         if (wq->spec.errorfunc)
 278           wq->spec.errorfunc (wq, item->data);
 279         work_queue_item_remove (wq, node);
 280         continue;
 281       }
 282
 283     /* run and take care of items that want to be retried immediately */
 284     do
 285       {
 286         ret = wq->spec.workfunc (wq, item->data);
 287         item->ran++;
 288       }
 289     while ((ret == WQ_RETRY_NOW)
 290            && (item->ran < wq->spec.max_retries));
 291
 292     switch (ret)
 293       {
 294       case WQ_QUEUE_BLOCKED:
 295         {
 296           /* decrement item->ran again, cause this isn't an item
 297            * specific error, and fall through to WQ_RETRY_LATER
 298            */
 299           item->ran--;
 300         }
 301       case WQ_RETRY_LATER:
 302         {
 303           goto stats;
 304         }
 305       case WQ_REQUEUE:
 306         {
 307           item->ran--;
 308           work_queue_item_requeue (wq, node);
 309           break;
 310         }
 311       case WQ_RETRY_NOW:
 312         /* a RETRY_NOW that gets here has exceeded max_tries, same as ERROR */
 313       case WQ_ERROR:
 314         {
 315           if (wq->spec.errorfunc)
 316             wq->spec.errorfunc (wq, item);
 317         }
 318         /* fall through here is deliberate */
 319       case WQ_SUCCESS:
 320       default:
 321         {
 322           work_queue_item_remove (wq, node);
 323           break;
 324         }
 325       }
 326
 327     /* completed cycle */
 328     cycles++;
 329
 330     /* test if we should yield */
 331     if ( !(cycles % wq->cycles.granularity)
 332         && thread_should_yield (thread))
 333       {
 334         yielded = 1;
 335         goto stats;
 336       }
 337   }
 338
 339 stats:
 340
 341 #define WQ_HYSTERIS_FACTOR 2
 342
 343   /* we yielded, check whether granularity should be reduced */
 344   if (yielded && (cycles < wq->cycles.granularity))
 345     {
 346       wq->cycles.granularity = ((cycles > 0) ? cycles
 347                                              : WORK_QUEUE_MIN_GRANULARITY);
 348     }
 349
 350   if (cycles >= (wq->cycles.granularity))
 351     {
 352       if (cycles > wq->cycles.best)
 353         wq->cycles.best = cycles;
 354
 355       /* along with yielded check, provides hysteris for granularity */
 356       if (cycles > (wq->cycles.granularity * WQ_HYSTERIS_FACTOR * 2))
 357         wq->cycles.granularity *= WQ_HYSTERIS_FACTOR; /* quick ramp-up */
 358       else if (cycles > (wq->cycles.granularity * WQ_HYSTERIS_FACTOR))
 359         wq->cycles.granularity += WQ_HYSTERIS_FACTOR;
 360     }
 361 #undef WQ_HYSTERIS_FACTOR
 362
 363   wq->runs++;
 364   wq->cycles.total += cycles;
 365
 366 #if 0
 367   printf ("%s: cycles %d, new: best %d, worst %d\n",
 368             __func__, cycles, wq->cycles.best, wq->cycles.granularity);
 369 #endif
 370
 371   /* Is the queue done yet? If it is, call the completion callback. */
 372   if (listcount (wq->items) > 0)
 373     work_queue_schedule (wq, 0);
 374   else if (wq->spec.completion_func)
 375     wq->spec.completion_func (wq);
 376
 377   return 0;
 378 }