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, int isblkdev); 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 int vm_swapcache_inactive_heuristic; 99 static int vm_swapcache_sleep; 100 static int vm_swapcache_maxlaunder = 256; 101 static int vm_swapcache_data_enable = 0; 102 static int vm_swapcache_meta_enable = 0; 103 static int vm_swapcache_maxswappct = 75; 104 static int vm_swapcache_hysteresis; 105 static int vm_swapcache_use_chflags = 1; /* require chflags cache */ 106 static int64_t vm_swapcache_minburst = 10000000LL; /* 10MB */ 107 static int64_t vm_swapcache_curburst = 4000000000LL; /* 4G after boot */ 108 static int64_t vm_swapcache_maxburst = 2000000000LL; /* 2G nominal max */ 109 static int64_t vm_swapcache_accrate = 100000LL; /* 100K/s */ 110 static int64_t vm_swapcache_write_count; 111 static int64_t vm_swapcache_maxfilesize; 112 113 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxlaunder, 114 CTLFLAG_RW, &vm_swapcache_maxlaunder, 0, ""); 115 116 SYSCTL_INT(_vm_swapcache, OID_AUTO, data_enable, 117 CTLFLAG_RW, &vm_swapcache_data_enable, 0, ""); 118 SYSCTL_INT(_vm_swapcache, OID_AUTO, meta_enable, 119 CTLFLAG_RW, &vm_swapcache_meta_enable, 0, ""); 120 SYSCTL_INT(_vm_swapcache, OID_AUTO, read_enable, 121 CTLFLAG_RW, &vm_swapcache_read_enable, 0, ""); 122 SYSCTL_INT(_vm_swapcache, OID_AUTO, maxswappct, 123 CTLFLAG_RW, &vm_swapcache_maxswappct, 0, ""); 124 SYSCTL_INT(_vm_swapcache, OID_AUTO, hysteresis, 125 CTLFLAG_RW, &vm_swapcache_hysteresis, 0, ""); 126 SYSCTL_INT(_vm_swapcache, OID_AUTO, use_chflags, 127 CTLFLAG_RW, &vm_swapcache_use_chflags, 0, ""); 128 129 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, minburst, 130 CTLFLAG_RW, &vm_swapcache_minburst, 0, ""); 131 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, curburst, 132 CTLFLAG_RW, &vm_swapcache_curburst, 0, ""); 133 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxburst, 134 CTLFLAG_RW, &vm_swapcache_maxburst, 0, ""); 135 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, maxfilesize, 136 CTLFLAG_RW, &vm_swapcache_maxfilesize, 0, ""); 137 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, accrate, 138 CTLFLAG_RW, &vm_swapcache_accrate, 0, ""); 139 SYSCTL_QUAD(_vm_swapcache, OID_AUTO, write_count, 140 CTLFLAG_RW, &vm_swapcache_write_count, 0, ""); 141 142 #define SWAPMAX(adj) \ 143 ((int64_t)vm_swap_max * (vm_swapcache_maxswappct + (adj)) / 100) 144 145 /* 146 * vm_swapcached is the high level pageout daemon. 147 */ 148 static void 149 vm_swapcached(void) 150 { 151 enum { SWAPC_WRITING, SWAPC_CLEANING } state = SWAPC_WRITING; 152 enum { SWAPB_BURSTING, SWAPB_RECOVERING } burst = SWAPB_BURSTING; 153 struct vm_page page_marker; 154 struct vm_object object_marker; 155 156 /* 157 * Thread setup 158 */ 159 curthread->td_flags |= TDF_SYSTHREAD; 160 crit_enter(); 161 162 /* 163 * Initialize our marker for the inactive scan (SWAPC_WRITING) 164 */ 165 bzero(&page_marker, sizeof(page_marker)); 166 page_marker.flags = PG_BUSY | PG_FICTITIOUS | PG_MARKER; 167 page_marker.queue = PQ_INACTIVE; 168 page_marker.wire_count = 1; 169 TAILQ_INSERT_HEAD(INACTIVE_LIST, &page_marker, pageq); 170 vm_swapcache_hysteresis = vmstats.v_inactive_target / 2; 171 vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis; 172 173 /* 174 * Initialize our marker for the vm_object scan (SWAPC_CLEANING) 175 */ 176 bzero(&object_marker, sizeof(object_marker)); 177 object_marker.type = OBJT_MARKER; 178 TAILQ_INSERT_HEAD(&vm_object_list, &object_marker, object_list); 179 180 for (;;) { 181 /* 182 * Check every 5 seconds when not enabled or if no swap 183 * is present. 184 */ 185 if ((vm_swapcache_data_enable == 0 && 186 vm_swapcache_meta_enable == 0) || 187 vm_swap_max == 0) { 188 tsleep(&vm_swapcache_sleep, 0, "csleep", hz * 5); 189 continue; 190 } 191 192 /* 193 * Polling rate when enabled is approximately 10 hz. 194 */ 195 tsleep(&vm_swapcache_sleep, 0, "csleep", hz / 10); 196 197 /* 198 * State hysteresis. Generate write activity up to 75% of 199 * swap, then clean out swap assignments down to 70%, then 200 * repeat. 201 */ 202 if (state == SWAPC_WRITING) { 203 if (vm_swap_cache_use > SWAPMAX(0)) 204 state = SWAPC_CLEANING; 205 } else { 206 if (vm_swap_cache_use < SWAPMAX(-5)) 207 state = SWAPC_WRITING; 208 } 209 210 /* 211 * We are allowed to continue accumulating burst value 212 * in either state. Allow the user to set curburst > maxburst 213 * for the initial load-in. 214 */ 215 if (vm_swapcache_curburst < vm_swapcache_maxburst) { 216 vm_swapcache_curburst += vm_swapcache_accrate / 10; 217 if (vm_swapcache_curburst > vm_swapcache_maxburst) 218 vm_swapcache_curburst = vm_swapcache_maxburst; 219 } 220 221 /* 222 * We don't want to nickle-and-dime the scan as that will 223 * create unnecessary fragmentation. The minimum burst 224 * is one-seconds worth of accumulation. 225 */ 226 if (state == SWAPC_WRITING) { 227 if (vm_swapcache_curburst >= vm_swapcache_accrate) { 228 if (burst == SWAPB_BURSTING) { 229 vm_swapcache_writing(&page_marker); 230 if (vm_swapcache_curburst <= 0) 231 burst = SWAPB_RECOVERING; 232 } else if (vm_swapcache_curburst > 233 vm_swapcache_minburst) { 234 vm_swapcache_writing(&page_marker); 235 burst = SWAPB_BURSTING; 236 } 237 } 238 } else { 239 vm_swapcache_cleaning(&object_marker); 240 } 241 } 242 TAILQ_REMOVE(INACTIVE_LIST, &page_marker, pageq); 243 TAILQ_REMOVE(&vm_object_list, &object_marker, object_list); 244 crit_exit(); 245 } 246 247 static void 248 vm_swapcache_writing(vm_page_t marker) 249 { 250 vm_object_t object; 251 struct vnode *vp; 252 vm_page_t m; 253 int count; 254 int isblkdev; 255 256 /* 257 * Deal with an overflow of the heuristic counter or if the user 258 * manually changes the hysteresis. 259 * 260 * Try to avoid small incremental pageouts by waiting for enough 261 * pages to buildup in the inactive queue to hopefully get a good 262 * burst in. This heuristic is bumped by the VM system and reset 263 * when our scan hits the end of the queue. 264 */ 265 if (vm_swapcache_inactive_heuristic < -vm_swapcache_hysteresis) 266 vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis; 267 if (vm_swapcache_inactive_heuristic < 0) 268 return; 269 270 /* 271 * Scan the inactive queue from our marker to locate 272 * suitable pages to push to the swap cache. 273 * 274 * We are looking for clean vnode-backed pages. 275 * 276 * NOTE: PG_SWAPPED pages in particular are not part of 277 * our count because once the cache stabilizes we 278 * can end up with a very high datarate of VM pages 279 * cycling from it. 280 */ 281 m = marker; 282 count = vm_swapcache_maxlaunder; 283 284 while ((m = TAILQ_NEXT(m, pageq)) != NULL && count--) { 285 if (m->flags & (PG_MARKER | PG_SWAPPED)) { 286 ++count; 287 continue; 288 } 289 if (vm_swapcache_curburst < 0) 290 break; 291 if (vm_swapcache_test(m)) 292 continue; 293 object = m->object; 294 vp = object->handle; 295 if (vp == NULL) 296 continue; 297 298 switch(vp->v_type) { 299 case VREG: 300 /* 301 * If data_enable is 0 do not try to swapcache data. 302 * If use_chflags is set then only swapcache data for 303 * VSWAPCACHE marked vnodes, otherwise any vnode. 304 */ 305 if (vm_swapcache_data_enable == 0 || 306 ((vp->v_flag & VSWAPCACHE) == 0 && 307 vm_swapcache_use_chflags)) { 308 continue; 309 } 310 if (vm_swapcache_maxfilesize && 311 object->size > 312 (vm_swapcache_maxfilesize >> PAGE_SHIFT)) { 313 continue; 314 } 315 isblkdev = 0; 316 break; 317 case VCHR: 318 /* 319 * The PG_NOTMETA flag only applies to pages 320 * associated with block devices. 321 */ 322 if (m->flags & PG_NOTMETA) 323 continue; 324 if (vm_swapcache_meta_enable == 0) 325 continue; 326 isblkdev = 1; 327 break; 328 default: 329 continue; 330 } 331 332 /* 333 * Ok, move the marker and soft-busy the page. 334 */ 335 TAILQ_REMOVE(INACTIVE_LIST, marker, pageq); 336 TAILQ_INSERT_AFTER(INACTIVE_LIST, m, marker, pageq); 337 338 /* 339 * Assign swap and initiate I/O. 340 * 341 * (adjust for the --count which also occurs in the loop) 342 */ 343 count -= vm_swapcached_flush(m, isblkdev) - 1; 344 345 /* 346 * Setup for next loop using marker. 347 */ 348 m = marker; 349 } 350 351 /* 352 * Cleanup marker position. If we hit the end of the 353 * list the marker is placed at the tail. Newly deactivated 354 * pages will be placed after it. 355 * 356 * Earlier inactive pages that were dirty and become clean 357 * are typically moved to the end of PQ_INACTIVE by virtue 358 * of vfs_vmio_release() when they become unwired from the 359 * buffer cache. 360 */ 361 TAILQ_REMOVE(INACTIVE_LIST, marker, pageq); 362 if (m) { 363 TAILQ_INSERT_BEFORE(m, marker, pageq); 364 } else { 365 TAILQ_INSERT_TAIL(INACTIVE_LIST, marker, pageq); 366 vm_swapcache_inactive_heuristic = -vm_swapcache_hysteresis; 367 } 368 } 369 370 /* 371 * Flush the specified page using the swap_pager. 372 * 373 * Try to collect surrounding pages, including pages which may 374 * have already been assigned swap. Try to cluster within a 375 * contiguous aligned SMAP_META_PAGES (typ 16 x PAGE_SIZE) block 376 * to match what swap_pager_putpages() can do. 377 * 378 * We also want to try to match against the buffer cache blocksize 379 * but we don't really know what it is here. Since the buffer cache 380 * wires and unwires pages in groups the fact that we skip wired pages 381 * should be sufficient. 382 * 383 * Returns a count of pages we might have flushed (minimum 1) 384 */ 385 static 386 int 387 vm_swapcached_flush(vm_page_t m, int isblkdev) 388 { 389 vm_object_t object; 390 vm_page_t marray[SWAP_META_PAGES]; 391 vm_pindex_t basei; 392 int rtvals[SWAP_META_PAGES]; 393 int x; 394 int i; 395 int j; 396 int count; 397 398 vm_page_io_start(m); 399 vm_page_protect(m, VM_PROT_READ); 400 object = m->object; 401 402 /* 403 * Try to cluster around (m), keeping in mind that the swap pager 404 * can only do SMAP_META_PAGES worth of continguous write. 405 */ 406 x = (int)m->pindex & SWAP_META_MASK; 407 marray[x] = m; 408 basei = m->pindex; 409 410 for (i = x - 1; i >= 0; --i) { 411 m = vm_page_lookup(object, basei - x + i); 412 if (m == NULL) 413 break; 414 if (vm_swapcache_test(m)) 415 break; 416 if (isblkdev && (m->flags & PG_NOTMETA)) 417 break; 418 vm_page_io_start(m); 419 vm_page_protect(m, VM_PROT_READ); 420 if (m->queue - m->pc == PQ_CACHE) { 421 vm_page_unqueue_nowakeup(m); 422 vm_page_deactivate(m); 423 } 424 marray[i] = m; 425 } 426 ++i; 427 428 for (j = x + 1; j < SWAP_META_PAGES; ++j) { 429 m = vm_page_lookup(object, basei - x + j); 430 if (m == NULL) 431 break; 432 if (vm_swapcache_test(m)) 433 break; 434 if (isblkdev && (m->flags & PG_NOTMETA)) 435 break; 436 vm_page_io_start(m); 437 vm_page_protect(m, VM_PROT_READ); 438 if (m->queue - m->pc == PQ_CACHE) { 439 vm_page_unqueue_nowakeup(m); 440 vm_page_deactivate(m); 441 } 442 marray[j] = m; 443 } 444 445 count = j - i; 446 vm_object_pip_add(object, count); 447 swap_pager_putpages(object, marray + i, count, FALSE, rtvals + i); 448 vm_swapcache_write_count += count * PAGE_SIZE; 449 vm_swapcache_curburst -= count * PAGE_SIZE; 450 451 while (i < j) { 452 if (rtvals[i] != VM_PAGER_PEND) { 453 vm_page_io_finish(marray[i]); 454 vm_object_pip_wakeup(object); 455 } 456 ++i; 457 } 458 return(count); 459 } 460 461 /* 462 * Test whether a VM page is suitable for writing to the swapcache. 463 * Does not test m->queue, PG_MARKER, or PG_SWAPPED. 464 * 465 * Returns 0 on success, 1 on failure 466 */ 467 static int 468 vm_swapcache_test(vm_page_t m) 469 { 470 vm_object_t object; 471 472 if (m->flags & (PG_BUSY | PG_UNMANAGED)) 473 return(1); 474 if (m->busy || m->hold_count || m->wire_count) 475 return(1); 476 if (m->valid != VM_PAGE_BITS_ALL) 477 return(1); 478 if (m->dirty & m->valid) 479 return(1); 480 if ((object = m->object) == NULL) 481 return(1); 482 if (object->type != OBJT_VNODE || 483 (object->flags & OBJ_DEAD)) { 484 return(1); 485 } 486 vm_page_test_dirty(m); 487 if (m->dirty & m->valid) 488 return(1); 489 return(0); 490 } 491 492 /* 493 * Cleaning pass 494 */ 495 static 496 void 497 vm_swapcache_cleaning(vm_object_t marker) 498 { 499 vm_object_t object; 500 struct vnode *vp; 501 int count; 502 int n; 503 504 object = marker; 505 count = vm_swapcache_maxlaunder; 506 507 /* 508 * Look for vnode objects 509 */ 510 while ((object = TAILQ_NEXT(object, object_list)) != NULL && count--) { 511 if (object->type != OBJT_VNODE) 512 continue; 513 if ((object->flags & OBJ_DEAD) || object->swblock_count == 0) 514 continue; 515 if ((vp = object->handle) == NULL) 516 continue; 517 if (vp->v_type != VREG && vp->v_type != VCHR) 518 continue; 519 520 /* 521 * Adjust iterator. 522 */ 523 if (marker->backing_object != object) 524 marker->size = 0; 525 526 /* 527 * Move the marker so we can work on the VM object 528 */ 529 TAILQ_REMOVE(&vm_object_list, marker, object_list); 530 TAILQ_INSERT_AFTER(&vm_object_list, object, 531 marker, object_list); 532 533 /* 534 * Look for swblocks starting at our iterator. 535 * 536 * The swap_pager_condfree() function attempts to free 537 * swap space starting at the specified index. The index 538 * will be updated on return. The function will return 539 * a scan factor (NOT the number of blocks freed). 540 * 541 * If it must cut its scan of the object short due to an 542 * excessive number of swblocks, or is able to free the 543 * requested number of blocks, it will return n >= count 544 * and we break and pick it back up on a future attempt. 545 */ 546 n = swap_pager_condfree(object, &marker->size, count); 547 count -= n; 548 if (count < 0) 549 break; 550 551 /* 552 * Setup for loop. 553 */ 554 marker->size = 0; 555 object = marker; 556 } 557 558 /* 559 * Adjust marker so we continue the scan from where we left off. 560 * When we reach the end we start back at the beginning. 561 */ 562 TAILQ_REMOVE(&vm_object_list, marker, object_list); 563 if (object) 564 TAILQ_INSERT_BEFORE(object, marker, object_list); 565 else 566 TAILQ_INSERT_HEAD(&vm_object_list, marker, object_list); 567 marker->backing_object = object; 568 } 569