sys/vm/vm_swapcache.c

   1 /*
   2  * Copyright (c) 2010 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.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
  35 /*
  36  * Implement the swapcache daemon.  When enabled swap is assumed to be
  37  * configured on a fast storage device such as a SSD.  Swap is assigned
  38  * to clean vnode-backed pages in the inactive queue, clustered by object
  39  * if possible, and written out.  The swap assignment sticks around even
  40  * after the underlying pages have been recycled.
  41  *
  42  * The daemon manages write bandwidth based on sysctl settings to control
  43  * wear on the SSD.
  44  *
  45  * The vnode strategy code will check for the swap assignments and divert
  46  * reads to the swap device when the data is present in the swapcache.
  47  *
  48  * This operates on both regular files and the block device vnodes used by
  49  * filesystems to manage meta-data.
  50  */
  51
  52 #include "opt_vm.h"
  53 #include <sys/param.h>
  54 #include <sys/systm.h>
  55 #include <sys/kernel.h>
  56 #include <sys/proc.h>
  57 #include <sys/kthread.h>
  58 #include <sys/resourcevar.h>
  59 #include <sys/signalvar.h>
  60 #include <sys/vnode.h>
  61 #include <sys/vmmeter.h>
  62 #include <sys/sysctl.h>
  63
  64 #include <vm/vm.h>
  65 #include <vm/vm_param.h>
  66 #include <sys/lock.h>
  67 #include <vm/vm_object.h>
  68 #include <vm/vm_page.h>
  69 #include <vm/vm_map.h>
  70 #include <vm/vm_pageout.h>
  71 #include <vm/vm_pager.h>
  72 #include <vm/swap_pager.h>
  73 #include <vm/vm_extern.h>
  74
  75 #include <sys/thread2.h>
  76 #include <vm/vm_page2.h>
  77
  78 #define INACTIVE_LIST   (&vm_page_queues[PQ_INACTIVE].pl)
  79
  80 /* the kernel process "vm_pageout"*/
  81 static void vm_swapcached (void);
  82 static int vm_swapcached_flush (vm_page_t m);
  83 static int vm_swapcache_test(vm_page_t m);
  84 static void vm_swapcache_writing(vm_page_t marker);
  85 static void vm_swapcache_cleaning(vm_object_t marker);
  86 struct thread *swapcached_thread;
  87
  88 static struct kproc_desc swpc_kp = {
  89         "swapcached",
  90         vm_swapcached,
  91         &swapcached_thread
  92 };
  93 SYSINIT(swapcached, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, &swpc_kp)
  94
  95 SYSCTL_NODE(_vm, OID_AUTO, swapcache, CTLFLAG_RW, NULL, NULL);
  96
  97 int vm_swapcache_read_enable;
  98 static int vm_swapcache_sleep;
  99 static int vm_swapcache_maxlaunder = 256;
 100 static int vm_swapcache_data_enable = 0;
 101 static int vm_swapcache_meta_enable = 0;
 102 static int vm_swapcache_maxswappct = 75;
 103 static int vm_swapcache_use_chflags = 1;        /* require chflags cache */
 104 static int64_t vm_swapcache_minburst = 10000000LL;      /* 10MB */
 105 static int64_t vm_swapcache_curburst = 4000000000LL;    /* 4G after boot */
 106 static int64_t vm_swapcache_maxburst = 2000000000LL;    /* 2G nominal max */
 107 static int64_t vm_swapcache_accrate = 100000LL;         /* 100K/s */
 108 static int64_t vm_swapcache_write_count;
 109 static int64_t vm_swapcache_maxfilesize;
 110
 111 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxlaunder,
 112         CTLFLAG_RW, &vm_swapcache_maxlaunder, 0, "");
 113
 114 SYSCTL_INT(_vm_swapcache, OID_AUTO, data_enable,
 115         CTLFLAG_RW, &vm_swapcache_data_enable, 0, "");
 116 SYSCTL_INT(_vm_swapcache, OID_AUTO, meta_enable,
 117         CTLFLAG_RW, &vm_swapcache_meta_enable, 0, "");
 118 SYSCTL_INT(_vm_swapcache, OID_AUTO, read_enable,
 119         CTLFLAG_RW, &vm_swapcache_read_enable, 0, "");
 120 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxswappct,
 121         CTLFLAG_RW, &vm_swapcache_maxswappct, 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  * vm_swapcached is the high level pageout daemon.
 143  */
 144 static void
 145 vm_swapcached(void)
 146 {
 147         enum { SWAPC_WRITING, SWAPC_CLEANING } state = SWAPC_WRITING;
 148         enum { SWAPB_BURSTING, SWAPB_RECOVERING } burst = SWAPB_BURSTING;
 149         struct vm_page page_marker;
 150         struct vm_object object_marker;
 151
 152         /*
 153          * Thread setup
 154          */
 155         curthread->td_flags |= TDF_SYSTHREAD;
 156         crit_enter();
 157
 158         /*
 159          * Initialize our marker for the inactive scan (SWAPC_WRITING)
 160          */
 161         bzero(&page_marker, sizeof(page_marker));
 162         page_marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
 163         page_marker.queue = PQ_INACTIVE;
 164         page_marker.wire_count = 1;
 165         TAILQ_INSERT_HEAD(INACTIVE_LIST, &page_marker, pageq);
 166
 167         /*
 168          * Initialize our marker for the vm_object scan (SWAPC_CLEANING)
 169          */
 170         bzero(&object_marker, sizeof(object_marker));
 171         object_marker.type = OBJT_MARKER;
 172         TAILQ_INSERT_HEAD(&vm_object_list, &object_marker, object_list);
 173
 174         for (;;) {
 175                 /*
 176                  * Check every 5 seconds when not enabled or if no swap
 177                  * is present.
 178                  */
 179                 if ((vm_swapcache_data_enable == 0 &&
 180                      vm_swapcache_meta_enable == 0) ||
 181                     vm_swap_max == 0) {
 182                         tsleep(&vm_swapcache_sleep, 0, "csleep", hz * 5);
 183                         continue;
 184                 }
 185
 186                 /*
 187                  * Polling rate when enabled is approximately 10 hz.
 188                  */
 189                 tsleep(&vm_swapcache_sleep, 0, "csleep", hz / 10);
 190
 191                 /*
 192                  * State hysteresis.  Generate write activity up to 75% of
 193                  * swap, then clean out swap assignments down to 70%, then
 194                  * repeat.
 195                  */
 196                 if (state == SWAPC_WRITING) {
 197                         if (vm_swap_cache_use > SWAPMAX(0))
 198                                 state = SWAPC_CLEANING;
 199                 } else {
 200                         if (vm_swap_cache_use < SWAPMAX(-5))
 201                                 state = SWAPC_WRITING;
 202                 }
 203
 204                 /*
 205                  * We are allowed to continue accumulating burst value
 206                  * in either state.  Allow the user to set curburst > maxburst
 207                  * for the initial load-in.
 208                  */
 209                 if (vm_swapcache_curburst < vm_swapcache_maxburst) {
 210                         vm_swapcache_curburst += vm_swapcache_accrate / 10;
 211                         if (vm_swapcache_curburst > vm_swapcache_maxburst)
 212                                 vm_swapcache_curburst = vm_swapcache_maxburst;
 213                 }
 214
 215                 /*
 216                  * We don't want to nickle-and-dime the scan as that will
 217                  * create unnecessary fragmentation.  The minimum burst
 218                  * is one-seconds worth of accumulation.
 219                  */
 220                 if (state == SWAPC_WRITING) {
 221                         if (vm_swapcache_curburst >= vm_swapcache_accrate) {
 222                                 if (burst == SWAPB_BURSTING) {
 223                                         vm_swapcache_writing(&page_marker);
 224                                         if (vm_swapcache_curburst <= 0)
 225                                                 burst = SWAPB_RECOVERING;
 226                                 } else if (vm_swapcache_curburst >
 227                                            vm_swapcache_minburst) {
 228                                         vm_swapcache_writing(&page_marker);
 229                                         burst = SWAPB_BURSTING;
 230                                 }
 231                         }
 232                 } else {
 233                         vm_swapcache_cleaning(&object_marker);
 234                 }
 235         }
 236         TAILQ_REMOVE(INACTIVE_LIST, &page_marker, pageq);
 237         TAILQ_REMOVE(&vm_object_list, &object_marker, object_list);
 238         crit_exit();
 239 }
 240
 241 static void
 242 vm_swapcache_writing(vm_page_t marker)
 243 {
 244         vm_object_t object;
 245         struct vnode *vp;
 246         vm_page_t m;
 247         int count;
 248
 249         /*
 250          * Scan the inactive queue from our marker to locate
 251          * suitable pages to push to the swap cache.
 252          *
 253          * We are looking for clean vnode-backed pages.
 254          *
 255          * NOTE: PG_SWAPPED pages in particular are not part of
 256          *       our count because once the cache stabilizes we
 257          *       can end up with a very high datarate of VM pages
 258          *       cycling from it.
 259          */
 260         m = marker;
 261         count = vm_swapcache_maxlaunder;
 262
 263         while ((m = TAILQ_NEXT(m, pageq)) != NULL && count--) {
 264                 if (m->flags & (PG_MARKER | PG_SWAPPED)) {
 265                         ++count;
 266                         continue;
 267                 }
 268                 if (vm_swapcache_curburst < 0)
 269                         break;
 270                 if (vm_swapcache_test(m))
 271                         continue;
 272                 object = m->object;
 273                 vp = object->handle;
 274                 if (vp == NULL)
 275                         continue;
 276
 277                 switch(vp->v_type) {
 278                 case VREG:
 279                         /*
 280                          * If data_enable is 0 do not try to swapcache data.
 281                          * If use_chflags is set then only swapcache data for
 282                          * VSWAPCACHE marked vnodes, otherwise any vnode.
 283                          */
 284                         if (vm_swapcache_data_enable == 0 ||
 285                             ((vp->v_flag & VSWAPCACHE) == 0 &&
 286                              vm_swapcache_use_chflags)) {
 287                                 continue;
 288                         }
 289                         if (vm_swapcache_maxfilesize &&
 290                             object->size >
 291                             (vm_swapcache_maxfilesize >> PAGE_SHIFT)) {
 292                                 continue;
 293                         }
 294                         break;
 295                 case VCHR:
 296                         if (vm_swapcache_meta_enable == 0)
 297                                 continue;
 298                         break;
 299                 default:
 300                         continue;
 301                 }
 302
 303                 /*
 304                  * Ok, move the marker and soft-busy the page.
 305                  */
 306                 TAILQ_REMOVE(INACTIVE_LIST, marker, pageq);
 307                 TAILQ_INSERT_AFTER(INACTIVE_LIST, m, marker, pageq);
 308
 309                 /*
 310                  * Assign swap and initiate I/O.
 311                  *
 312                  * (adjust for the --count which also occurs in the loop)
 313                  */
 314                 count -= vm_swapcached_flush(m) - 1;
 315
 316                 /*
 317                  * Setup for next loop using marker.
 318                  */
 319                 m = marker;
 320         }
 321
 322         /*
 323          * Cleanup marker position.  If we hit the end of the
 324          * list the marker is placed at the tail.  Newly deactivated
 325          * pages will be placed after it.
 326          *
 327          * Earlier inactive pages that were dirty and become clean
 328          * are typically moved to the end of PQ_INACTIVE by virtue
 329          * of vfs_vmio_release() when they become unwired from the
 330          * buffer cache.
 331          */
 332         TAILQ_REMOVE(INACTIVE_LIST, marker, pageq);
 333         if (m)
 334                 TAILQ_INSERT_BEFORE(m, marker, pageq);
 335         else
 336                 TAILQ_INSERT_TAIL(INACTIVE_LIST, marker, pageq);
 337 }
 338
 339 /*
 340  * Flush the specified page using the swap_pager.
 341  *
 342  * Try to collect surrounding pages, including pages which may
 343  * have already been assigned swap.  Try to cluster within a
 344  * contiguous aligned SMAP_META_PAGES (typ 16 x PAGE_SIZE) block
 345  * to match what swap_pager_putpages() can do.
 346  *
 347  * We also want to try to match against the buffer cache blocksize
 348  * but we don't really know what it is here.  Since the buffer cache
 349  * wires and unwires pages in groups the fact that we skip wired pages
 350  * should be sufficient.
 351  *
 352  * Returns a count of pages we might have flushed (minimum 1)
 353  */
 354 static
 355 int
 356 vm_swapcached_flush(vm_page_t m)
 357 {
 358         vm_object_t object;
 359         vm_page_t marray[SWAP_META_PAGES];
 360         vm_pindex_t basei;
 361         int rtvals[SWAP_META_PAGES];
 362         int x;
 363         int i;
 364         int j;
 365         int count;
 366
 367         vm_page_io_start(m);
 368         vm_page_protect(m, VM_PROT_READ);
 369         object = m->object;
 370
 371         /*
 372          * Try to cluster around (m), keeping in mind that the swap pager
 373          * can only do SMAP_META_PAGES worth of continguous write.
 374          */
 375         x = (int)m->pindex & SWAP_META_MASK;
 376         marray[x] = m;
 377         basei = m->pindex;
 378
 379         for (i = x - 1; i >= 0; --i) {
 380                 m = vm_page_lookup(object, basei - x + i);
 381                 if (m == NULL)
 382                         break;
 383                 if (vm_swapcache_test(m))
 384                         break;
 385                 vm_page_io_start(m);
 386                 vm_page_protect(m, VM_PROT_READ);
 387                 if (m->queue - m->pc == PQ_CACHE) {
 388                         vm_page_unqueue_nowakeup(m);
 389                         vm_page_deactivate(m);
 390                 }
 391                 marray[i] = m;
 392         }
 393         ++i;
 394
 395         for (j = x + 1; j < SWAP_META_PAGES; ++j) {
 396                 m = vm_page_lookup(object, basei - x + j);
 397                 if (m == NULL)
 398                         break;
 399                 if (vm_swapcache_test(m))
 400                         break;
 401                 vm_page_io_start(m);
 402                 vm_page_protect(m, VM_PROT_READ);
 403                 if (m->queue - m->pc == PQ_CACHE) {
 404                         vm_page_unqueue_nowakeup(m);
 405                         vm_page_deactivate(m);
 406                 }
 407                 marray[j] = m;
 408         }
 409
 410         count = j - i;
 411         vm_object_pip_add(object, count);
 412         swap_pager_putpages(object, marray + i, count, FALSE, rtvals + i);
 413         vm_swapcache_write_count += count * PAGE_SIZE;
 414         vm_swapcache_curburst -= count * PAGE_SIZE;
 415
 416         while (i < j) {
 417                 if (rtvals[i] != VM_PAGER_PEND) {
 418                         vm_page_io_finish(marray[i]);
 419                         vm_object_pip_wakeup(object);
 420                 }
 421                 ++i;
 422         }
 423         return(count);
 424 }
 425
 426 /*
 427  * Test whether a VM page is suitable for writing to the swapcache.
 428  * Does not test m->queue, PG_MARKER, or PG_SWAPPED.
 429  *
 430  * Returns 0 on success, 1 on failure
 431  */
 432 static int
 433 vm_swapcache_test(vm_page_t m)
 434 {
 435         vm_object_t object;
 436
 437         if (m->flags & (PG_BUSY | PG_UNMANAGED | PG_NOTMETA))
 438                 return(1);
 439         if (m->busy || m->hold_count || m->wire_count)
 440                 return(1);
 441         if (m->valid != VM_PAGE_BITS_ALL)
 442                 return(1);
 443         if (m->dirty & m->valid)
 444                 return(1);
 445         if ((object = m->object) == NULL)
 446                 return(1);
 447         if (object->type != OBJT_VNODE ||
 448             (object->flags & OBJ_DEAD)) {
 449                 return(1);
 450         }
 451         vm_page_test_dirty(m);
 452         if (m->dirty & m->valid)
 453                 return(1);
 454         return(0);
 455 }
 456
 457 /*
 458  * Cleaning pass
 459  */
 460 static
 461 void
 462 vm_swapcache_cleaning(vm_object_t marker)
 463 {
 464         vm_object_t object;
 465         struct vnode *vp;
 466         int count;
 467         int n;
 468
 469         object = marker;
 470         count = vm_swapcache_maxlaunder;
 471
 472         /*
 473          * Look for vnode objects
 474          */
 475         while ((object = TAILQ_NEXT(object, object_list)) != NULL && count--) {
 476                 if (object->type != OBJT_VNODE)
 477                         continue;
 478                 if ((object->flags & OBJ_DEAD) || object->swblock_count == 0)
 479                         continue;
 480                 if ((vp = object->handle) == NULL)
 481                         continue;
 482                 if (vp->v_type != VREG && vp->v_type != VCHR)
 483                         continue;
 484
 485                 /*
 486                  * Adjust iterator.
 487                  */
 488                 if (marker->backing_object != object)
 489                         marker->size = 0;
 490
 491                 /*
 492                  * Move the marker so we can work on the VM object
 493                  */
 494                 TAILQ_REMOVE(&vm_object_list, marker, object_list);
 495                 TAILQ_INSERT_AFTER(&vm_object_list, object,
 496                                    marker, object_list);
 497
 498                 /*
 499                  * Look for swblocks starting at our iterator.
 500                  *
 501                  * The swap_pager_condfree() function attempts to free
 502                  * swap space starting at the specified index.  The index
 503                  * will be updated on return.  The function will return
 504                  * a scan factor (NOT the number of blocks freed).
 505                  *
 506                  * If it must cut its scan of the object short due to an
 507                  * excessive number of swblocks, or is able to free the
 508                  * requested number of blocks, it will return n >= count
 509                  * and we break and pick it back up on a future attempt.
 510                  */
 511                 n = swap_pager_condfree(object, &marker->size, count);
 512                 count -= n;
 513                 if (count < 0)
 514                         break;
 515
 516                 /*
 517                  * Setup for loop.
 518                  */
 519                 marker->size = 0;
 520                 object = marker;
 521         }
 522
 523         /*
 524          * Adjust marker so we continue the scan from where we left off.
 525          * When we reach the end we start back at the beginning.
 526          */
 527         TAILQ_REMOVE(&vm_object_list, marker, object_list);
 528         if (object)
 529                 TAILQ_INSERT_BEFORE(object, marker, object_list);
 530         else
 531                 TAILQ_INSERT_HEAD(&vm_object_list, marker, object_list);
 532         marker->backing_object = object;
 533 }