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.
  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 void vm_swapcached_flush (vm_page_t m);
  83 struct thread *swapcached_thread;
  84
  85 static struct kproc_desc swpc_kp = {
  86         "swapcached",
  87         vm_swapcached,
  88         &swapcached_thread
  89 };
  90 SYSINIT(swapcached, SI_SUB_KTHREAD_PAGE, SI_ORDER_SECOND, kproc_start, &swpc_kp)
  91
  92 SYSCTL_NODE(_vm, OID_AUTO, swapcache, CTLFLAG_RW, NULL, NULL);
  93
  94 int vm_swapcache_read_enable;
  95 static int vm_swapcache_sleep;
  96 static int vm_swapcache_maxlaunder = 128;
  97 static int vm_swapcache_data_enable = 0;
  98 static int vm_swapcache_meta_enable = 0;
  99 static int64_t vm_swapcache_curburst = 1000000000LL;
 100 static int64_t vm_swapcache_maxburst = 1000000000LL;
 101 static int64_t vm_swapcache_accrate = 1000000LL;
 102 static int64_t vm_swapcache_write_count;
 103
 104 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxlaunder,
 105         CTLFLAG_RW, &vm_swapcache_maxlaunder, 0, "");
 106
 107 SYSCTL_INT(_vm_swapcache, OID_AUTO, data_enable,
 108         CTLFLAG_RW, &vm_swapcache_data_enable, 0, "");
 109 SYSCTL_INT(_vm_swapcache, OID_AUTO, meta_enable,
 110         CTLFLAG_RW, &vm_swapcache_meta_enable, 0, "");
 111 SYSCTL_INT(_vm_swapcache, OID_AUTO, read_enable,
 112         CTLFLAG_RW, &vm_swapcache_read_enable, 0, "");
 113
 114 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, curburst,
 115         CTLFLAG_RW, &vm_swapcache_curburst, 0, "");
 116 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxburst,
 117         CTLFLAG_RW, &vm_swapcache_maxburst, 0, "");
 118 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, accrate,
 119         CTLFLAG_RW, &vm_swapcache_accrate, 0, "");
 120 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, write_count,
 121         CTLFLAG_RW, &vm_swapcache_write_count, 0, "");
 122
 123 /*
 124  * vm_swapcached is the high level pageout daemon.
 125  */
 126 static void
 127 vm_swapcached(void)
 128 {
 129         struct vm_page marker;
 130         vm_object_t object;
 131         struct vnode *vp;
 132         vm_page_t m;
 133         int count;
 134
 135         /*
 136          * Thread setup
 137          */
 138         curthread->td_flags |= TDF_SYSTHREAD;
 139
 140         /*
 141          * Initialize our marker
 142          */
 143         bzero(&marker, sizeof(marker));
 144         marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER;
 145         marker.queue = PQ_INACTIVE;
 146         marker.wire_count = 1;
 147
 148         crit_enter();
 149         TAILQ_INSERT_HEAD(INACTIVE_LIST, &marker, pageq);
 150
 151         for (;;) {
 152                 /*
 153                  * Loop once a second or so looking for work when enabled.
 154                  */
 155                 if (vm_swapcache_data_enable == 0 &&
 156                     vm_swapcache_meta_enable == 0) {
 157                         tsleep(&vm_swapcache_sleep, 0, "csleep", hz * 5);
 158                         continue;
 159                 }
 160
 161                 /*
 162                  * Polling rate when enabled is 10 hz.  Deal with write
 163                  * bandwidth limits.
 164                  *
 165                  * We don't want to nickle-and-dime the scan as that will
 166                  * create unnecessary fragmentation.
 167                  */
 168                 tsleep(&vm_swapcache_sleep, 0, "csleep", hz / 10);
 169                 vm_swapcache_curburst += vm_swapcache_accrate / 10;
 170                 if (vm_swapcache_curburst > vm_swapcache_maxburst)
 171                         vm_swapcache_curburst = vm_swapcache_maxburst;
 172                 if (vm_swapcache_curburst < vm_swapcache_accrate)
 173                         continue;
 174
 175                 /*
 176                  * Don't load any more into the cache once we have exceeded
 177                  * 2/3 of available swap space.  XXX need to start cleaning
 178                  * it out, though vnode recycling will accomplish that to
 179                  * some degree.
 180                  */
 181                 if (vm_swap_cache_use > vm_swap_size * 2 / 3)
 182                         continue;
 183
 184                 /*
 185                  * Calculate the number of pages to test.  We don't want
 186                  * to get into a cpu-bound loop.
 187                  */
 188                 count = vmstats.v_inactive_count;
 189                 if (count > vm_swapcache_maxlaunder)
 190                         count = vm_swapcache_maxlaunder;
 191
 192                 /*
 193                  * Scan the inactive queue from our marker to locate
 194                  * suitable pages to push to the swap cache.
 195                  *
 196                  * We are looking for clean vnode-backed pages.
 197                  */
 198                 m = &marker;
 199                 while ((m = TAILQ_NEXT(m, pageq)) != NULL && count--) {
 200                         if (m->flags & PG_MARKER) {
 201                                 ++count;
 202                                 continue;
 203                         }
 204                         if (vm_swapcache_curburst < 0)
 205                                 break;
 206                         if (m->flags & (PG_SWAPPED | PG_BUSY | PG_UNMANAGED))
 207                                 continue;
 208                         if (m->busy || m->hold_count || m->wire_count)
 209                                 continue;
 210                         if (m->valid != VM_PAGE_BITS_ALL)
 211                                 continue;
 212                         if (m->dirty & m->valid)
 213                                 continue;
 214                         if ((object = m->object) == NULL)
 215                                 continue;
 216                         if (object->type != OBJT_VNODE ||
 217                             (object->flags & OBJ_DEAD)) {
 218                                 continue;
 219                         }
 220                         vm_page_test_dirty(m);
 221                         if (m->dirty & m->valid)
 222                                 continue;
 223                         vp = object->handle;
 224                         if (vp == NULL)
 225                                 continue;
 226                         switch(vp->v_type) {
 227                         case VREG:
 228                                 if (vm_swapcache_data_enable == 0)
 229                                         continue;
 230                                 break;
 231                         case VCHR:
 232                                 if (vm_swapcache_meta_enable == 0)
 233                                         continue;
 234                                 break;
 235                         default:
 236                                 continue;
 237                         }
 238
 239                         /*
 240                          * Ok, move the marker and soft-busy the page.
 241                          */
 242                         TAILQ_REMOVE(INACTIVE_LIST, &marker, pageq);
 243                         TAILQ_INSERT_AFTER(INACTIVE_LIST, m, &marker, pageq);
 244
 245                         /*
 246                          * Assign swap and initiate I/O
 247                          */
 248                         vm_swapcached_flush(m);
 249
 250                         /*
 251                          * Setup for next loop using marker.
 252                          */
 253                         m = &marker;
 254                 }
 255                 TAILQ_REMOVE(INACTIVE_LIST, &marker, pageq);
 256                 if (m)
 257                         TAILQ_INSERT_BEFORE(m, &marker, pageq);
 258                 else
 259                         TAILQ_INSERT_HEAD(INACTIVE_LIST, &marker, pageq);
 260
 261         }
 262         TAILQ_REMOVE(INACTIVE_LIST, &marker, pageq);
 263         crit_exit();
 264 }
 265
 266 /*
 267  * Flush the specified page using the swap_pager.
 268  */
 269 static
 270 void
 271 vm_swapcached_flush(vm_page_t m)
 272 {
 273         vm_object_t object;
 274         int rtvals;
 275
 276         vm_page_io_start(m);
 277         vm_page_protect(m, VM_PROT_READ);
 278
 279         object = m->object;
 280         vm_object_pip_add(object, 1);
 281         swap_pager_putpages(object, &m, 1, FALSE, &rtvals);
 282         vm_swapcache_write_count += PAGE_SIZE;
 283         vm_swapcache_curburst -= PAGE_SIZE;
 284
 285         if (rtvals != VM_PAGER_PEND) {
 286                 vm_object_pip_wakeup(object);
 287                 vm_page_io_finish(m);
 288         }
 289 }