sys/vm/vm_swapcache.c

   1 /*
   2  * (MPSAFE)
   3  *
   4  * Copyright (c) 2010 The DragonFly Project.  All rights reserved.
   5  *
   6  * This code is derived from software contributed to The DragonFly Project
   7  * by Matthew Dillon <dillon@backplane.com>
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in
  17  *    the documentation and/or other materials provided with the
  18  *    distribution.
  19  * 3. Neither the name of The DragonFly Project nor the names of its
  20  *    contributors may be used to endorse or promote products derived
  21  *    from this software without specific, prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  24  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  25  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  26  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  27  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  28  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  29  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  30  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  31  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  32  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  33  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 /*
  38  * Implement the swapcache daemon.  When enabled swap is assumed to be
  39  * configured on a fast storage device such as a SSD.  Swap is assigned
  40  * to clean vnode-backed pages in the inactive queue, clustered by object
  41  * if possible, and written out.  The swap assignment sticks around even
  42  * after the underlying pages have been recycled.
  43  *
  44  * The daemon manages write bandwidth based on sysctl settings to control
  45  * wear on the SSD.
  46  *
  47  * The vnode strategy code will check for the swap assignments and divert
  48  * reads to the swap device when the data is present in the swapcache.
  49  *
  50  * This operates on both regular files and the block device vnodes used by
  51  * filesystems to manage meta-data.
  52  */
  53
  54 #include "opt_vm.h"
  55 #include <sys/param.h>
  56 #include <sys/systm.h>
  57 #include <sys/kernel.h>
  58 #include <sys/proc.h>
  59 #include <sys/kthread.h>
  60 #include <sys/resourcevar.h>
  61 #include <sys/signalvar.h>
  62 #include <sys/vnode.h>
  63 #include <sys/vmmeter.h>
  64 #include <sys/sysctl.h>
  65 #include <sys/eventhandler.h>
  66
  67 #include <vm/vm.h>
  68 #include <vm/vm_param.h>
  69 #include <sys/lock.h>
  70 #include <vm/vm_object.h>
  71 #include <vm/vm_page.h>
  72 #include <vm/vm_map.h>
  73 #include <vm/vm_pageout.h>
  74 #include <vm/vm_pager.h>
  75 #include <vm/swap_pager.h>
  76 #include <vm/vm_extern.h>
  77
  78 #include <sys/thread2.h>
  79 #include <sys/spinlock2.h>
  80 #include <vm/vm_page2.h>
  81
  82 #define INACTIVE_LIST   (&vm_page_queues[PQ_INACTIVE].pl)
  83
  84 /* the kernel process "vm_pageout"*/
  85 static int vm_swapcached_flush (vm_page_t m, int isblkdev);
  86 static int vm_swapcache_test(vm_page_t m);
  87 static void vm_swapcache_writing(vm_page_t marker);
  88 static void vm_swapcache_cleaning(vm_object_t marker);
  89 struct thread *swapcached_thread;
  90
  91 SYSCTL_NODE(_vm, OID_AUTO, swapcache, CTLFLAG_RW, NULL, NULL);
  92
  93 int vm_swapcache_read_enable;
  94 int vm_swapcache_inactive_heuristic;
  95 static int vm_swapcache_sleep;
  96 static int vm_swapcache_maxlaunder = 256;
  97 static int vm_swapcache_data_enable = 0;
  98 static int vm_swapcache_meta_enable = 0;
  99 static int vm_swapcache_maxswappct = 75;
 100 static int vm_swapcache_hysteresis;
 101 int vm_swapcache_use_chflags = 1;       /* require chflags cache */
 102 static int64_t vm_swapcache_minburst = 10000000LL;      /* 10MB */
 103 static int64_t vm_swapcache_curburst = 4000000000LL;    /* 4G after boot */
 104 static int64_t vm_swapcache_maxburst = 2000000000LL;    /* 2G nominal max */
 105 static int64_t vm_swapcache_accrate = 100000LL;         /* 100K/s */
 106 static int64_t vm_swapcache_write_count;
 107 static int64_t vm_swapcache_maxfilesize;
 108
 109 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxlaunder,
 110         CTLFLAG_RW, &vm_swapcache_maxlaunder, 0, "");
 111
 112 SYSCTL_INT(_vm_swapcache, OID_AUTO, data_enable,
 113         CTLFLAG_RW, &vm_swapcache_data_enable, 0, "");
 114 SYSCTL_INT(_vm_swapcache, OID_AUTO, meta_enable,
 115         CTLFLAG_RW, &vm_swapcache_meta_enable, 0, "");
 116 SYSCTL_INT(_vm_swapcache, OID_AUTO, read_enable,
 117         CTLFLAG_RW, &vm_swapcache_read_enable, 0, "");
 118 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxswappct,
 119         CTLFLAG_RW, &vm_swapcache_maxswappct, 0, "");
 120 SYSCTL_INT(_vm_swapcache, OID_AUTO, hysteresis,
 121         CTLFLAG_RW, &vm_swapcache_hysteresis, 0, "");
 122 SYSCTL_INT(_vm_swapcache, OID_AUTO, use_chflags,
 123         CTLFLAG_RW, &vm_swapcache_use_chflags, 0, "");
 124
 125 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, minburst,
 126         CTLFLAG_RW, &vm_swapcache_minburst, 0, "");
 127 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, curburst,
 128         CTLFLAG_RW, &vm_swapcache_curburst, 0, "");
 129 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxburst,
 130         CTLFLAG_RW, &vm_swapcache_maxburst, 0, "");
 131 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxfilesize,
 132         CTLFLAG_RW, &vm_swapcache_maxfilesize, 0, "");
 133 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, accrate,
 134         CTLFLAG_RW, &vm_swapcache_accrate, 0, "");
 135 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, write_count,
 136         CTLFLAG_RW, &vm_swapcache_write_count, 0, "");
 137
 138 #define SWAPMAX(adj)    \
 139         ((int64_t)vm_swap_max * (vm_swapcache_maxswappct + (adj)) / 100)
 140
 141 /*
 142  * When shutting down the machine we want to stop swapcache operation
 143  * immediately so swap is not accessed after devices have been shuttered.
 144  */
 145 static void
 146 shutdown_swapcache(void *arg __unused)
 147 {
 148         vm_swapcache_read_enable = 0;
 149         vm_swapcache_data_enable = 0;
 150         vm_swapcache_meta_enable = 0;
 151         wakeup(&vm_swapcache_sleep);    /* shortcut 5-second wait */
 152 }
 153
 154 /*
 155  * vm_swapcached is the high level pageout daemon.
 156  *
 157  * No requirements.
 158  */
 159 static void
 160 vm_swapcached_thread(void)
 161 {
 162         enum { SWAPC_WRITING, SWAPC_CLEANING } state = SWAPC_WRITING;
 163         enum { SWAPB_BURSTING, SWAPB_RECOVERING } burst = SWAPB_BURSTING;
 164         struct vm_page page_marker;
 165         struct vm_object object_marker;
 166
 167         /*
 168          * Thread setup
 169          */
 170         curthread->td_flags |= TDF_SYSTHREAD;
 171         EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc,
 172                               swapcached_thread, SHUTDOWN_PRI_FIRST);
 173         EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_swapcache,
 174                               NULL, SHUTDOWN_PRI_SECOND);
 175
 176         /*
 177          * Initialize our marker for the inactive scan (SWAPC_WRITING)
 178          */
 179         bzero(&page_marker, sizeof(page_marker));
 180         page_marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
 181         page_marker.queue = PQ_INACTIVE;
 182         page_marker.wire_count = 1;
 183
 184         vm_page_queues_spin_lock(PQ_INACTIVE);
 185         TAILQ_INSERT_HEAD(INACTIVE_LIST, &page_marker, pageq);
 186         vm_page_queues_spin_unlock(PQ_INACTIVE);
 187
 188         vm_swapcache_hysteresis = vmstats.v_inactive_target / 2;
 189         vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis;
 190
 191         /*
 192          * Initialize our marker for the vm_object scan (SWAPC_CLEANING)
 193          */
 194         bzero(&object_marker, sizeof(object_marker));
 195         object_marker.type = OBJT_MARKER;
 196         lwkt_gettoken(&vmobj_token);
 197         TAILQ_INSERT_HEAD(&vm_object_list, &object_marker, object_list);
 198         lwkt_reltoken(&vmobj_token);
 199
 200         for (;;) {
 201                 /*
 202                  * Handle shutdown
 203                  */
 204                 kproc_suspend_loop();
 205
 206                 /*
 207                  * Check every 5 seconds when not enabled or if no swap
 208                  * is present.
 209                  */
 210                 if ((vm_swapcache_data_enable == 0 &&
 211                      vm_swapcache_meta_enable == 0) ||
 212                     vm_swap_max == 0) {
 213                         tsleep(&vm_swapcache_sleep, 0, "csleep", hz * 5);
 214                         continue;
 215                 }
 216
 217                 /*
 218                  * Polling rate when enabled is approximately 10 hz.
 219                  */
 220                 tsleep(&vm_swapcache_sleep, 0, "csleep", hz / 10);
 221
 222                 /*
 223                  * State hysteresis.  Generate write activity up to 75% of
 224                  * swap, then clean out swap assignments down to 70%, then
 225                  * repeat.
 226                  */
 227                 if (state == SWAPC_WRITING) {
 228                         if (vm_swap_cache_use > SWAPMAX(0))
 229                                 state = SWAPC_CLEANING;
 230                 } else {
 231                         if (vm_swap_cache_use < SWAPMAX(-5))
 232                                 state = SWAPC_WRITING;
 233                 }
 234
 235                 /*
 236                  * We are allowed to continue accumulating burst value
 237                  * in either state.  Allow the user to set curburst > maxburst
 238                  * for the initial load-in.
 239                  */
 240                 if (vm_swapcache_curburst < vm_swapcache_maxburst) {
 241                         vm_swapcache_curburst += vm_swapcache_accrate / 10;
 242                         if (vm_swapcache_curburst > vm_swapcache_maxburst)
 243                                 vm_swapcache_curburst = vm_swapcache_maxburst;
 244                 }
 245
 246                 /*
 247                  * We don't want to nickle-and-dime the scan as that will
 248                  * create unnecessary fragmentation.  The minimum burst
 249                  * is one-seconds worth of accumulation.
 250                  */
 251                 if (state == SWAPC_WRITING) {
 252                         if (vm_swapcache_curburst >= vm_swapcache_accrate) {
 253                                 if (burst == SWAPB_BURSTING) {
 254                                         vm_swapcache_writing(&page_marker);
 255                                         if (vm_swapcache_curburst <= 0)
 256                                                 burst = SWAPB_RECOVERING;
 257                                 } else if (vm_swapcache_curburst >
 258                                            vm_swapcache_minburst) {
 259                                         vm_swapcache_writing(&page_marker);
 260                                         burst = SWAPB_BURSTING;
 261                                 }
 262                         }
 263                 } else {
 264                         vm_swapcache_cleaning(&object_marker);
 265                 }
 266         }
 267
 268         /*
 269          * Cleanup (NOT REACHED)
 270          */
 271         vm_page_queues_spin_lock(PQ_INACTIVE);
 272         TAILQ_REMOVE(INACTIVE_LIST, &page_marker, pageq);
 273         vm_page_queues_spin_unlock(PQ_INACTIVE);
 274
 275         lwkt_gettoken(&vmobj_token);
 276         TAILQ_REMOVE(&vm_object_list, &object_marker, object_list);
 277         lwkt_reltoken(&vmobj_token);
 278 }
 279
 280 static struct kproc_desc swpc_kp = {
 281         "swapcached",
 282         vm_swapcached_thread,
 283         &swapcached_thread
 284 };
 285 SYSINIT(swapcached, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, &swpc_kp)
 286
 287 static void
 288 vm_swapcache_writing(vm_page_t marker)
 289 {
 290         vm_object_t object;
 291         struct vnode *vp;
 292         vm_page_t m;
 293         int count;
 294         int isblkdev;
 295
 296         /*
 297          * Deal with an overflow of the heuristic counter or if the user
 298          * manually changes the hysteresis.
 299          *
 300          * Try to avoid small incremental pageouts by waiting for enough
 301          * pages to buildup in the inactive queue to hopefully get a good
 302          * burst in.  This heuristic is bumped by the VM system and reset
 303          * when our scan hits the end of the queue.
 304          */
 305         if (vm_swapcache_inactive_heuristic < -vm_swapcache_hysteresis)
 306                 vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis;
 307         if (vm_swapcache_inactive_heuristic < 0)
 308                 return;
 309
 310         /*
 311          * Scan the inactive queue from our marker to locate
 312          * suitable pages to push to the swap cache.
 313          *
 314          * We are looking for clean vnode-backed pages.
 315          *
 316          * NOTE: PG_SWAPPED pages in particular are not part of
 317          *       our count because once the cache stabilizes we
 318          *       can end up with a very high datarate of VM pages
 319          *       cycling from it.
 320          */
 321         count = vm_swapcache_maxlaunder;
 322
 323         vm_page_queues_spin_lock(PQ_INACTIVE);
 324         while ((m = TAILQ_NEXT(marker, pageq)) != NULL && count-- > 0) {
 325                 KKASSERT(m->queue == PQ_INACTIVE);
 326
 327                 if (vm_swapcache_curburst < 0)
 328                         break;
 329                 TAILQ_REMOVE(INACTIVE_LIST, marker, pageq);
 330                 TAILQ_INSERT_AFTER(INACTIVE_LIST, m, marker, pageq);
 331                 if (m->flags & (PG_MARKER | PG_SWAPPED)) {
 332                         ++count;
 333                         continue;
 334                 }
 335                 if (vm_page_busy_try(m, TRUE))
 336                         continue;
 337                 vm_page_queues_spin_unlock(PQ_INACTIVE);
 338
 339                 if ((object = m->object) == NULL) {
 340                         vm_page_wakeup(m);
 341                         vm_page_queues_spin_lock(PQ_INACTIVE);
 342                         continue;
 343                 }
 344                 vm_object_hold(object);
 345                 if (m->object != object) {
 346                         vm_object_drop(object);
 347                         vm_page_wakeup(m);
 348                         vm_page_queues_spin_lock(PQ_INACTIVE);
 349                         continue;
 350                 }
 351                 if (vm_swapcache_test(m)) {
 352                         vm_object_drop(object);
 353                         vm_page_wakeup(m);
 354                         vm_page_queues_spin_lock(PQ_INACTIVE);
 355                         continue;
 356                 }
 357
 358                 vp = object->handle;
 359                 if (vp == NULL) {
 360                         vm_object_drop(object);
 361                         vm_page_wakeup(m);
 362                         vm_page_queues_spin_lock(PQ_INACTIVE);
 363                         continue;
 364                 }
 365
 366                 switch(vp->v_type) {
 367                 case VREG:
 368                         /*
 369                          * PG_NOTMETA generically means 'don't swapcache this',
 370                          * and HAMMER will set this for regular data buffers
 371                          * (and leave it unset for meta-data buffers) as
 372                          * appropriate when double buffering is enabled.
 373                          */
 374                         if (m->flags & PG_NOTMETA) {
 375                                 vm_object_drop(object);
 376                                 vm_page_wakeup(m);
 377                                 vm_page_queues_spin_lock(PQ_INACTIVE);
 378                                 continue;
 379                         }
 380
 381                         /*
 382                          * If data_enable is 0 do not try to swapcache data.
 383                          * If use_chflags is set then only swapcache data for
 384                          * VSWAPCACHE marked vnodes, otherwise any vnode.
 385                          */
 386                         if (vm_swapcache_data_enable == 0 ||
 387                             ((vp->v_flag & VSWAPCACHE) == 0 &&
 388                              vm_swapcache_use_chflags)) {
 389                                 vm_object_drop(object);
 390                                 vm_page_wakeup(m);
 391                                 vm_page_queues_spin_lock(PQ_INACTIVE);
 392                                 continue;
 393                         }
 394                         if (vm_swapcache_maxfilesize &&
 395                             object->size >
 396                             (vm_swapcache_maxfilesize >> PAGE_SHIFT)) {
 397                                 vm_object_drop(object);
 398                                 vm_page_wakeup(m);
 399                                 vm_page_queues_spin_lock(PQ_INACTIVE);
 400                                 continue;
 401                         }
 402                         isblkdev = 0;
 403                         break;
 404                 case VCHR:
 405                         /*
 406                          * PG_NOTMETA generically means 'don't swapcache this',
 407                          * and HAMMER will set this for regular data buffers
 408                          * (and leave it unset for meta-data buffers) as
 409                          * appropriate when double buffering is enabled.
 410                          */
 411                         if (m->flags & PG_NOTMETA) {
 412                                 vm_object_drop(object);
 413                                 vm_page_wakeup(m);
 414                                 vm_page_queues_spin_lock(PQ_INACTIVE);
 415                                 continue;
 416                         }
 417                         if (vm_swapcache_meta_enable == 0) {
 418                                 vm_object_drop(object);
 419                                 vm_page_wakeup(m);
 420                                 vm_page_queues_spin_lock(PQ_INACTIVE);
 421                                 continue;
 422                         }
 423                         isblkdev = 1;
 424                         break;
 425                 default:
 426                         vm_object_drop(object);
 427                         vm_page_wakeup(m);
 428                         vm_page_queues_spin_lock(PQ_INACTIVE);
 429                         continue;
 430                 }
 431
 432
 433                 /*
 434                  * Assign swap and initiate I/O.
 435                  *
 436                  * (adjust for the --count which also occurs in the loop)
 437                  */
 438                 count -= vm_swapcached_flush(m, isblkdev) - 1;
 439
 440                 /*
 441                  * Setup for next loop using marker.
 442                  */
 443                 vm_object_drop(object);
 444                 vm_page_queues_spin_lock(PQ_INACTIVE);
 445         }
 446
 447         /*
 448          * The marker could wind up at the end, which is ok.  If we hit the
 449          * end of the list adjust the heuristic.
 450          *
 451          * Earlier inactive pages that were dirty and become clean
 452          * are typically moved to the end of PQ_INACTIVE by virtue
 453          * of vfs_vmio_release() when they become unwired from the
 454          * buffer cache.
 455          */
 456         if (m == NULL)
 457                 vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis;
 458         vm_page_queues_spin_unlock(PQ_INACTIVE);
 459 }
 460
 461 /*
 462  * Flush the specified page using the swap_pager.  The page
 463  * must be busied by the caller and its disposition will become
 464  * the responsibility of this function.
 465  *
 466  * Try to collect surrounding pages, including pages which may
 467  * have already been assigned swap.  Try to cluster within a
 468  * contiguous aligned SMAP_META_PAGES (typ 16 x PAGE_SIZE) block
 469  * to match what swap_pager_putpages() can do.
 470  *
 471  * We also want to try to match against the buffer cache blocksize
 472  * but we don't really know what it is here.  Since the buffer cache
 473  * wires and unwires pages in groups the fact that we skip wired pages
 474  * should be sufficient.
 475  *
 476  * Returns a count of pages we might have flushed (minimum 1)
 477  */
 478 static
 479 int
 480 vm_swapcached_flush(vm_page_t m, int isblkdev)
 481 {
 482         vm_object_t object;
 483         vm_page_t marray[SWAP_META_PAGES];
 484         vm_pindex_t basei;
 485         int rtvals[SWAP_META_PAGES];
 486         int x;
 487         int i;
 488         int j;
 489         int count;
 490         int error;
 491
 492         vm_page_io_start(m);
 493         vm_page_protect(m, VM_PROT_READ);
 494         object = m->object;
 495         vm_object_hold(object);
 496
 497         /*
 498          * Try to cluster around (m), keeping in mind that the swap pager
 499          * can only do SMAP_META_PAGES worth of continguous write.
 500          */
 501         x = (int)m->pindex & SWAP_META_MASK;
 502         marray[x] = m;
 503         basei = m->pindex;
 504         vm_page_wakeup(m);
 505
 506         for (i = x - 1; i >= 0; --i) {
 507                 m = vm_page_lookup_busy_try(object, basei - x + i,
 508                                             TRUE, &error);
 509                 if (error || m == NULL)
 510                         break;
 511                 if (vm_swapcache_test(m)) {
 512                         vm_page_wakeup(m);
 513                         break;
 514                 }
 515                 if (isblkdev && (m->flags & PG_NOTMETA)) {
 516                         vm_page_wakeup(m);
 517                         break;
 518                 }
 519                 vm_page_io_start(m);
 520                 vm_page_protect(m, VM_PROT_READ);
 521                 if (m->queue - m->pc == PQ_CACHE) {
 522                         vm_page_unqueue_nowakeup(m);
 523                         vm_page_deactivate(m);
 524                 }
 525                 marray[i] = m;
 526                 vm_page_wakeup(m);
 527         }
 528         ++i;
 529
 530         for (j = x + 1; j < SWAP_META_PAGES; ++j) {
 531                 m = vm_page_lookup_busy_try(object, basei - x + j,
 532                                             TRUE, &error);
 533                 if (error || m == NULL)
 534                         break;
 535                 if (vm_swapcache_test(m)) {
 536                         vm_page_wakeup(m);
 537                         break;
 538                 }
 539                 if (isblkdev && (m->flags & PG_NOTMETA)) {
 540                         vm_page_wakeup(m);
 541                         break;
 542                 }
 543                 vm_page_io_start(m);
 544                 vm_page_protect(m, VM_PROT_READ);
 545                 if (m->queue - m->pc == PQ_CACHE) {
 546                         vm_page_unqueue_nowakeup(m);
 547                         vm_page_deactivate(m);
 548                 }
 549                 marray[j] = m;
 550                 vm_page_wakeup(m);
 551         }
 552
 553         count = j - i;
 554         vm_object_pip_add(object, count);
 555         swap_pager_putpages(object, marray + i, count, FALSE, rtvals + i);
 556         vm_swapcache_write_count += count * PAGE_SIZE;
 557         vm_swapcache_curburst -= count * PAGE_SIZE;
 558
 559         while (i < j) {
 560                 if (rtvals[i] != VM_PAGER_PEND) {
 561                         vm_page_busy_wait(marray[i], FALSE, "swppgfd");
 562                         vm_page_io_finish(marray[i]);
 563                         vm_page_wakeup(marray[i]);
 564                         vm_object_pip_wakeup(object);
 565                 }
 566                 ++i;
 567         }
 568         vm_object_drop(object);
 569         return(count);
 570 }
 571
 572 /*
 573  * Test whether a VM page is suitable for writing to the swapcache.
 574  * Does not test m->queue, PG_MARKER, or PG_SWAPPED.
 575  *
 576  * Returns 0 on success, 1 on failure
 577  */
 578 static int
 579 vm_swapcache_test(vm_page_t m)
 580 {
 581         vm_object_t object;
 582
 583         if (m->flags & PG_UNMANAGED)
 584                 return(1);
 585         if (m->hold_count || m->wire_count)
 586                 return(1);
 587         if (m->valid != VM_PAGE_BITS_ALL)
 588                 return(1);
 589         if (m->dirty & m->valid)
 590                 return(1);
 591         if ((object = m->object) == NULL)
 592                 return(1);
 593         if (object->type != OBJT_VNODE ||
 594             (object->flags & OBJ_DEAD)) {
 595                 return(1);
 596         }
 597         vm_page_test_dirty(m);
 598         if (m->dirty & m->valid)
 599                 return(1);
 600         return(0);
 601 }
 602
 603 /*
 604  * Cleaning pass
 605  */
 606 static
 607 void
 608 vm_swapcache_cleaning(vm_object_t marker)
 609 {
 610         vm_object_t object;
 611         struct vnode *vp;
 612         int count;
 613         int n;
 614
 615         object = marker;
 616         count = vm_swapcache_maxlaunder;
 617
 618         /*
 619          * Look for vnode objects
 620          */
 621         lwkt_gettoken(&vmobj_token);
 622
 623         while ((object = TAILQ_NEXT(object, object_list)) != NULL) {
 624                 lwkt_yield();
 625                 if (--count <= 0)
 626                         break;
 627                 vm_object_hold(object);
 628
 629                 /*
 630                  * Only operate on live VNODE objects with regular/chardev types
 631                  */
 632                 if ((object->type != OBJT_VNODE) ||
 633                     ((object->flags & OBJ_DEAD) || object->swblock_count == 0) ||
 634                     ((vp = object->handle) == NULL) ||
 635                     (vp->v_type != VREG && vp->v_type != VCHR)) {
 636                         vm_object_drop(object);
 637                         continue;
 638                 }
 639
 640                 /*
 641                  * Adjust iterator.
 642                  */
 643                 if (marker->backing_object != object)
 644                         marker->size = 0;
 645
 646                 /*
 647                  * Move the marker so we can work on the VM object
 648                  */
 649                 TAILQ_REMOVE(&vm_object_list, marker, object_list);
 650                 TAILQ_INSERT_AFTER(&vm_object_list, object,
 651                                    marker, object_list);
 652
 653                 /*
 654                  * Look for swblocks starting at our iterator.
 655                  *
 656                  * The swap_pager_condfree() function attempts to free
 657                  * swap space starting at the specified index.  The index
 658                  * will be updated on return.  The function will return
 659                  * a scan factor (NOT the number of blocks freed).
 660                  *
 661                  * If it must cut its scan of the object short due to an
 662                  * excessive number of swblocks, or is able to free the
 663                  * requested number of blocks, it will return n >= count
 664                  * and we break and pick it back up on a future attempt.
 665                  */
 666                 n = swap_pager_condfree(object, &marker->size, count);
 667
 668                 vm_object_drop(object);
 669
 670                 count -= n;
 671                 if (count < 0)
 672                         break;
 673
 674                 /*
 675                  * Setup for loop.
 676                  */
 677                 marker->size = 0;
 678                 object = marker;
 679         }
 680
 681         /*
 682          * Adjust marker so we continue the scan from where we left off.
 683          * When we reach the end we start back at the beginning.
 684          */
 685         TAILQ_REMOVE(&vm_object_list, marker, object_list);
 686         if (object)
 687                 TAILQ_INSERT_BEFORE(object, marker, object_list);
 688         else
 689                 TAILQ_INSERT_HEAD(&vm_object_list, marker, object_list);
 690         marker->backing_object = object;
 691
 692         lwkt_reltoken(&vmobj_token);
 693 }