sys/kern/dsched/fq/fq_core.c

   1 /*
   2  * Copyright (c) 2009, 2010 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Alex Hornung <ahornung@gmail.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34 #include <sys/param.h>
  35 #include <sys/systm.h>
  36 #include <sys/kernel.h>
  37 #include <sys/proc.h>
  38 #include <sys/sysctl.h>
  39 #include <sys/buf.h>
  40 #include <sys/conf.h>
  41 #include <sys/diskslice.h>
  42 #include <sys/disk.h>
  43 #include <machine/atomic.h>
  44 #include <sys/thread.h>
  45 #include <sys/thread2.h>
  46 #include <sys/ctype.h>
  47 #include <sys/buf2.h>
  48 #include <sys/syslog.h>
  49 #include <sys/dsched.h>
  50 #include <machine/param.h>
  51
  52 #include <kern/dsched/fq/fq.h>
  53
  54 static int      dsched_fq_version_maj = 1;
  55 static int      dsched_fq_version_min = 1;
  56
  57 /* Make sure our structs fit */
  58 CTASSERT(sizeof(struct fq_thread_io) <= DSCHED_THREAD_IO_MAX_SZ);
  59 CTASSERT(sizeof(struct fq_disk_ctx) <= DSCHED_DISK_CTX_MAX_SZ);
  60
  61 struct dsched_fq_stats  fq_stats;
  62
  63 extern struct dsched_policy dsched_fq_policy;
  64
  65 void
  66 fq_dispatcher(struct fq_disk_ctx *diskctx)
  67 {
  68         struct dispatch_prep dispatch_ary[FQ_DISPATCH_ARRAY_SZ];
  69         struct dsched_thread_io *ds_tdio, *ds_tdio2;
  70         struct fq_thread_io     *tdio;
  71         struct bio *bio, *bio2;
  72         int idle;
  73         int i, prepd_io;
  74
  75         /*
  76          * We need to manually assign an tdio to the tdctx of this thread
  77          * since it isn't assigned one during fq_prepare, as the disk
  78          * is not set up yet.
  79          */
  80         tdio = (struct fq_thread_io *)dsched_new_policy_thread_tdio(&diskctx->head,
  81             &dsched_fq_policy);
  82
  83         DSCHED_DISK_CTX_LOCK(&diskctx->head);
  84         for(;;) {
  85                 idle = 0;
  86                 /* sleep ~60 ms */
  87                 if ((lksleep(diskctx, &diskctx->head.lock, 0, "fq_dispatcher", hz/15) == 0)) {
  88                         /*
  89                          * We've been woken up; this either means that we are
  90                          * supposed to die away nicely or that the disk is idle.
  91                          */
  92
  93                         if (__predict_false(diskctx->die == 1)) {
  94                                 /* If we are supposed to die, drain all queues */
  95                                 fq_drain(diskctx, FQ_DRAIN_FLUSH);
  96
  97                                 /* Now we can safely unlock and exit */
  98                                 DSCHED_DISK_CTX_UNLOCK(&diskctx->head);
  99                                 kprintf("fq_dispatcher is peacefully dying\n");
 100                                 lwkt_exit();
 101                                 /* NOTREACHED */
 102                         }
 103
 104                         /*
 105                          * We have been awakened because the disk is idle.
 106                          * So let's get ready to dispatch some extra bios.
 107                          */
 108                         idle = 1;
 109                 }
 110
 111                 /* Maybe the disk is idle and we just didn't get the wakeup */
 112                 if (idle == 0)
 113                         idle = diskctx->idle;
 114
 115                 /* Set the number of prepared requests to 0 */
 116                 i = 0;
 117
 118                 /*
 119                  * XXX: further room for improvements here. It would be better
 120                  *      to dispatch a few requests from each tdio as to ensure
 121                  *      real fairness.
 122                  */
 123                 TAILQ_FOREACH_MUTABLE(ds_tdio, &diskctx->head.tdio_list, dlink, ds_tdio2) {
 124                         tdio = (struct fq_thread_io *)ds_tdio;
 125                         if (tdio->head.qlength == 0)
 126                                 continue;
 127
 128                         DSCHED_THREAD_IO_LOCK(&tdio->head);
 129                         if (atomic_cmpset_int(&tdio->rebalance, 1, 0))
 130                                 fq_balance_self(tdio);
 131                         /*
 132                          * XXX: why 5 extra? should probably be dynamic,
 133                          *      relying on information on latency.
 134                          */
 135                         if ((tdio->max_tp > 0) && idle &&
 136                             (tdio->issued >= tdio->max_tp)) {
 137                                 tdio->max_tp += 5;
 138                         }
 139
 140                         prepd_io = 0;
 141                         TAILQ_FOREACH_MUTABLE(bio, &tdio->head.queue, link, bio2) {
 142                                 if (atomic_cmpset_int(&tdio->rebalance, 1, 0))
 143                                         fq_balance_self(tdio);
 144                                 if (((tdio->max_tp > 0) &&
 145                                     (tdio->issued + prepd_io >= tdio->max_tp)) ||
 146                                     (i == FQ_DISPATCH_ARRAY_SZ))
 147                                         break;
 148
 149                                 TAILQ_REMOVE(&tdio->head.queue, bio, link);
 150                                 --tdio->head.qlength;
 151
 152                                 /*
 153                                  * beware that we do have an tdio reference
 154                                  * from the queueing
 155                                  *
 156                                  * XXX: note that here we don't dispatch it yet
 157                                  *      but just prepare it for dispatch so
 158                                  *      that no locks are held when calling
 159                                  *      into the drivers.
 160                                  */
 161                                 dispatch_ary[i].bio = bio;
 162                                 dispatch_ary[i].tdio = tdio;
 163                                 ++i;
 164                                 ++prepd_io;
 165                         }
 166                         DSCHED_THREAD_IO_UNLOCK(&tdio->head);
 167
 168                 }
 169
 170                 dsched_disk_ctx_ref(&diskctx->head);
 171                 DSCHED_DISK_CTX_UNLOCK(&diskctx->head);
 172
 173                 /*
 174                  * Dispatch all the previously prepared bios, now without
 175                  * holding any locks.
 176                  */
 177                 for (--i; i >= 0; i--) {
 178                         bio = dispatch_ary[i].bio;
 179                         tdio = dispatch_ary[i].tdio;
 180                         fq_dispatch(diskctx, bio, tdio);
 181                 }
 182
 183                 DSCHED_DISK_CTX_LOCK(&diskctx->head);
 184                 dsched_disk_ctx_unref(&diskctx->head);
 185         }
 186 }
 187
 188 void
 189 fq_balance_thread(struct fq_disk_ctx *diskctx)
 190 {
 191         struct dsched_thread_io *ds_tdio;
 192         struct  fq_thread_io    *tdio;
 193         struct timeval tv, old_tv;
 194         int64_t total_budget, product;
 195         int64_t budget[FQ_PRIO_MAX+1];
 196         int     n, i, sum, total_disk_time;
 197         int     lost_bits;
 198
 199         DSCHED_DISK_CTX_LOCK(&diskctx->head);
 200
 201         getmicrotime(&diskctx->start_interval);
 202
 203         for (;;) {
 204                 /* sleep ~1s */
 205                 if ((lksleep(curthread, &diskctx->head.lock, 0, "fq_balancer", hz/2) == 0)) {
 206                         if (__predict_false(diskctx->die)) {
 207                                 DSCHED_DISK_CTX_UNLOCK(&diskctx->head);
 208                                 lwkt_exit();
 209                         }
 210                 }
 211
 212                 bzero(budget, sizeof(budget));
 213                 total_budget = 0;
 214                 n = 0;
 215
 216                 old_tv = diskctx->start_interval;
 217                 getmicrotime(&tv);
 218
 219                 total_disk_time = (int)(1000000*((tv.tv_sec - old_tv.tv_sec)) +
 220                     (tv.tv_usec - old_tv.tv_usec));
 221
 222                 if (total_disk_time == 0)
 223                         total_disk_time = 1;
 224
 225                 dsched_debug(LOG_INFO, "total_disk_time = %d\n", total_disk_time);
 226
 227                 diskctx->start_interval = tv;
 228
 229                 diskctx->disk_busy = (100*(total_disk_time - diskctx->idle_time)) / total_disk_time;
 230                 if (diskctx->disk_busy < 0)
 231                         diskctx->disk_busy = 0;
 232
 233                 diskctx->idle_time = 0;
 234                 lost_bits = 0;
 235
 236                 TAILQ_FOREACH(ds_tdio, &diskctx->head.tdio_list, dlink) {
 237                         tdio = (struct fq_thread_io *)ds_tdio;
 238                         tdio->interval_avg_latency = tdio->avg_latency;
 239                         tdio->interval_transactions = tdio->transactions;
 240                         if (tdio->interval_transactions > 0) {
 241                                 product = (int64_t)tdio->interval_avg_latency *
 242                                     tdio->interval_transactions;
 243                                 product >>= lost_bits;
 244                                 while(total_budget >= INT64_MAX - product) {
 245                                         ++lost_bits;
 246                                         product >>= 1;
 247                                         total_budget >>= 1;
 248                                 }
 249                                 total_budget += product;
 250                                 ++budget[(tdio->head.p) ? tdio->head.p->p_ionice : 0];
 251                                 KKASSERT(total_budget >= 0);
 252                                 dsched_debug(LOG_INFO,
 253                                     "%d) avg_latency = %d, transactions = %d, ioprio = %d\n",
 254                                     n, tdio->interval_avg_latency, tdio->interval_transactions,
 255                                     (tdio->head.p) ? tdio->head.p->p_ionice : 0);
 256                                 ++n;
 257                         } else {
 258                                 tdio->max_tp = 0;
 259                         }
 260                         tdio->rebalance = 0;
 261                         tdio->transactions = 0;
 262                         tdio->avg_latency = 0;
 263                         tdio->issued = 0;
 264                 }
 265
 266                 dsched_debug(LOG_INFO, "%d procs competing for disk\n"
 267                     "total_budget = %jd (lost bits = %d)\n"
 268                     "incomplete tp = %d\n", n, (intmax_t)total_budget,
 269                     lost_bits, diskctx->incomplete_tp);
 270
 271                 if (n == 0)
 272                         continue;
 273
 274                 sum = 0;
 275
 276                 for (i = 0; i < FQ_PRIO_MAX+1; i++) {
 277                         if (budget[i] == 0)
 278                                 continue;
 279                         sum += (FQ_PRIO_BIAS+i)*budget[i];
 280                 }
 281
 282                 if (sum == 0)
 283                         sum = 1;
 284
 285                 dsched_debug(LOG_INFO, "sum = %d\n", sum);
 286
 287                 for (i = 0; i < FQ_PRIO_MAX+1; i++) {
 288                         if (budget[i] == 0)
 289                                 continue;
 290
 291                         /*
 292                          * XXX: if we still overflow here, we really need to switch to
 293                          *      some more advanced mechanism such as compound int128 or
 294                          *      storing the lost bits so they can be used in the
 295                          *      fq_balance_self.
 296                          */
 297                         diskctx->budgetpb[i] = ((FQ_PRIO_BIAS+i)*total_budget/sum) << lost_bits;
 298                         KKASSERT(diskctx->budgetpb[i] >= 0);
 299                 }
 300
 301                 dsched_debug(4, "disk is %d%% busy\n", diskctx->disk_busy);
 302                 TAILQ_FOREACH(ds_tdio, &diskctx->head.tdio_list, dlink) {
 303                         tdio = (struct fq_thread_io *)ds_tdio;
 304                         tdio->rebalance = 1;
 305                 }
 306
 307                 diskctx->prev_full = diskctx->last_full;
 308                 diskctx->last_full = (diskctx->disk_busy >= 90)?1:0;
 309         }
 310 }
 311
 312
 313 /*
 314  * fq_balance_self should be called from all sorts of dispatchers. It basically
 315  * offloads some of the heavier calculations on throttling onto the process that
 316  * wants to do I/O instead of doing it in the fq_balance thread.
 317  * - should be called with diskctx lock held
 318  */
 319 void
 320 fq_balance_self(struct fq_thread_io *tdio) {
 321         struct fq_disk_ctx *diskctx;
 322
 323         int64_t budget, used_budget;
 324         int64_t avg_latency;
 325         int64_t transactions;
 326
 327         transactions = (int64_t)tdio->interval_transactions;
 328         avg_latency = (int64_t)tdio->interval_avg_latency;
 329         diskctx = (struct fq_disk_ctx *)tdio->head.diskctx;
 330
 331 #if 0
 332         /* XXX: do we really require the lock? */
 333         DSCHED_DISK_CTX_LOCK_ASSERT(diskctx);
 334 #endif
 335
 336         used_budget = ((int64_t)avg_latency * transactions);
 337         budget = diskctx->budgetpb[(tdio->head.p) ? tdio->head.p->p_ionice : 0];
 338
 339         if (used_budget > 0) {
 340                 dsched_debug(LOG_INFO,
 341                     "info: used_budget = %jd, budget = %jd\n",
 342                     (intmax_t)used_budget, budget);
 343         }
 344
 345         if ((used_budget > budget) && (diskctx->disk_busy >= 90)) {
 346                 KKASSERT(avg_latency != 0);
 347
 348                 tdio->max_tp = budget/(avg_latency);
 349                 atomic_add_int(&fq_stats.procs_limited, 1);
 350
 351                 dsched_debug(LOG_INFO,
 352                     "rate limited to %d transactions\n", tdio->max_tp);
 353
 354         } else if (((used_budget*2 < budget) || (diskctx->disk_busy < 80)) &&
 355             (!diskctx->prev_full && !diskctx->last_full)) {
 356                 tdio->max_tp = 0;
 357         }
 358 }
 359
 360
 361 static int
 362 do_fqstats(SYSCTL_HANDLER_ARGS)
 363 {
 364         return (sysctl_handle_opaque(oidp, &fq_stats, sizeof(struct dsched_fq_stats), req));
 365 }
 366
 367 static int
 368 fq_mod_handler(module_t mod, int type, void *unused)
 369 {
 370         static struct sysctl_ctx_list sysctl_ctx;
 371         static struct sysctl_oid *oid;
 372         static char version[16];
 373         int error;
 374
 375         ksnprintf(version, sizeof(version), "%d.%d",
 376             dsched_fq_version_maj, dsched_fq_version_min);
 377
 378         switch (type) {
 379         case MOD_LOAD:
 380                 bzero(&fq_stats, sizeof(struct dsched_fq_stats));
 381                 if ((error = dsched_register(&dsched_fq_policy)))
 382                         return (error);
 383
 384                 sysctl_ctx_init(&sysctl_ctx);
 385                 oid = SYSCTL_ADD_NODE(&sysctl_ctx,
 386                     SYSCTL_STATIC_CHILDREN(_dsched),
 387                     OID_AUTO,
 388                     "fq",
 389                     CTLFLAG_RD, 0, "");
 390
 391                 SYSCTL_ADD_PROC(&sysctl_ctx, SYSCTL_CHILDREN(oid),
 392                     OID_AUTO, "stats", CTLTYPE_OPAQUE|CTLFLAG_RD,
 393                     0, 0, do_fqstats, "S,dsched_fq_stats", "fq statistics");
 394
 395                 SYSCTL_ADD_STRING(&sysctl_ctx, SYSCTL_CHILDREN(oid),
 396                     OID_AUTO, "version", CTLFLAG_RD, version, 0, "fq version");
 397
 398                 kprintf("FQ scheduler policy version %d.%d loaded\n",
 399                     dsched_fq_version_maj, dsched_fq_version_min);
 400                 break;
 401
 402         case MOD_UNLOAD:
 403                 if ((error = dsched_unregister(&dsched_fq_policy)))
 404                         return (error);
 405                 sysctl_ctx_free(&sysctl_ctx);
 406                 kprintf("FQ scheduler policy unloaded\n");
 407                 break;
 408
 409         default:
 410                 break;
 411         }
 412
 413         return 0;
 414 }
 415
 416 DSCHED_POLICY_MODULE(dsched_fq, fq_mod_handler);