1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or https://opensource.org/licenses/CDDL-1.0. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2018, Joyent, Inc. 24 * Copyright (c) 2011, 2019 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 #include <sys/spa.h> 30 #include <sys/zio.h> 31 #include <sys/spa_impl.h> 32 #include <sys/zio_compress.h> 33 #include <sys/zio_checksum.h> 34 #include <sys/zfs_context.h> 35 #include <sys/arc.h> 36 #include <sys/zfs_refcount.h> 37 #include <sys/vdev.h> 38 #include <sys/vdev_trim.h> 39 #include <sys/vdev_impl.h> 40 #include <sys/dsl_pool.h> 41 #include <sys/multilist.h> 42 #include <sys/abd.h> 43 #include <sys/zil.h> 44 #include <sys/fm/fs/zfs.h> 45 #ifdef _KERNEL 46 #include <sys/shrinker.h> 47 #include <sys/vmsystm.h> 48 #include <sys/zpl.h> 49 #include <linux/page_compat.h> 50 #include <linux/notifier.h> 51 #include <linux/memory.h> 52 #endif 53 #include <sys/callb.h> 54 #include <sys/kstat.h> 55 #include <sys/zthr.h> 56 #include <zfs_fletcher.h> 57 #include <sys/arc_impl.h> 58 #include <sys/trace_zfs.h> 59 #include <sys/aggsum.h> 60 61 /* 62 * This is a limit on how many pages the ARC shrinker makes available for 63 * eviction in response to one page allocation attempt. Note that in 64 * practice, the kernel's shrinker can ask us to evict up to about 4x this 65 * for one allocation attempt. 66 * 67 * The default limit of 10,000 (in practice, 160MB per allocation attempt 68 * with 4K pages) limits the amount of time spent attempting to reclaim ARC 69 * memory to less than 100ms per allocation attempt, even with a small 70 * average compressed block size of ~8KB. 71 * 72 * See also the comment in arc_shrinker_count(). 73 * Set to 0 to disable limit. 74 */ 75 int zfs_arc_shrinker_limit = 10000; 76 77 #ifdef CONFIG_MEMORY_HOTPLUG 78 static struct notifier_block arc_hotplug_callback_mem_nb; 79 #endif 80 81 /* 82 * Return a default max arc size based on the amount of physical memory. 83 */ 84 uint64_t 85 arc_default_max(uint64_t min, uint64_t allmem) 86 { 87 /* Default to 1/2 of all memory. */ 88 return (MAX(allmem / 2, min)); 89 } 90 91 #ifdef _KERNEL 92 /* 93 * Return maximum amount of memory that we could possibly use. Reduced 94 * to half of all memory in user space which is primarily used for testing. 95 */ 96 uint64_t 97 arc_all_memory(void) 98 { 99 #ifdef CONFIG_HIGHMEM 100 return (ptob(zfs_totalram_pages - zfs_totalhigh_pages)); 101 #else 102 return (ptob(zfs_totalram_pages)); 103 #endif /* CONFIG_HIGHMEM */ 104 } 105 106 /* 107 * Return the amount of memory that is considered free. In user space 108 * which is primarily used for testing we pretend that free memory ranges 109 * from 0-20% of all memory. 110 */ 111 uint64_t 112 arc_free_memory(void) 113 { 114 #ifdef CONFIG_HIGHMEM 115 struct sysinfo si; 116 si_meminfo(&si); 117 return (ptob(si.freeram - si.freehigh)); 118 #else 119 return (ptob(nr_free_pages() + 120 nr_inactive_file_pages())); 121 #endif /* CONFIG_HIGHMEM */ 122 } 123 124 /* 125 * Return the amount of memory that can be consumed before reclaim will be 126 * needed. Positive if there is sufficient free memory, negative indicates 127 * the amount of memory that needs to be freed up. 128 */ 129 int64_t 130 arc_available_memory(void) 131 { 132 return (arc_free_memory() - arc_sys_free); 133 } 134 135 static uint64_t 136 arc_evictable_memory(void) 137 { 138 int64_t asize = aggsum_value(&arc_sums.arcstat_size); 139 uint64_t arc_clean = 140 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_DATA]) + 141 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_METADATA]) + 142 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_DATA]) + 143 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 144 uint64_t arc_dirty = MAX((int64_t)asize - (int64_t)arc_clean, 0); 145 146 /* 147 * Scale reported evictable memory in proportion to page cache, cap 148 * at specified min/max. 149 */ 150 uint64_t min = (ptob(nr_file_pages()) / 100) * zfs_arc_pc_percent; 151 min = MAX(arc_c_min, MIN(arc_c_max, min)); 152 153 if (arc_dirty >= min) 154 return (arc_clean); 155 156 return (MAX((int64_t)asize - (int64_t)min, 0)); 157 } 158 159 /* 160 * The _count() function returns the number of free-able objects. 161 * The _scan() function returns the number of objects that were freed. 162 */ 163 static unsigned long 164 arc_shrinker_count(struct shrinker *shrink, struct shrink_control *sc) 165 { 166 /* 167 * __GFP_FS won't be set if we are called from ZFS code (see 168 * kmem_flags_convert(), which removes it). To avoid a deadlock, we 169 * don't allow evicting in this case. We return 0 rather than 170 * SHRINK_STOP so that the shrinker logic doesn't accumulate a 171 * deficit against us. 172 */ 173 if (!(sc->gfp_mask & __GFP_FS)) { 174 return (0); 175 } 176 177 /* 178 * This code is reached in the "direct reclaim" case, where the 179 * kernel (outside ZFS) is trying to allocate a page, and the system 180 * is low on memory. 181 * 182 * The kernel's shrinker code doesn't understand how many pages the 183 * ARC's callback actually frees, so it may ask the ARC to shrink a 184 * lot for one page allocation. This is problematic because it may 185 * take a long time, thus delaying the page allocation, and because 186 * it may force the ARC to unnecessarily shrink very small. 187 * 188 * Therefore, we limit the amount of data that we say is evictable, 189 * which limits the amount that the shrinker will ask us to evict for 190 * one page allocation attempt. 191 * 192 * In practice, we may be asked to shrink 4x the limit to satisfy one 193 * page allocation, before the kernel's shrinker code gives up on us. 194 * When that happens, we rely on the kernel code to find the pages 195 * that we freed before invoking the OOM killer. This happens in 196 * __alloc_pages_slowpath(), which retries and finds the pages we 197 * freed when it calls get_page_from_freelist(). 198 * 199 * See also the comment above zfs_arc_shrinker_limit. 200 */ 201 int64_t limit = zfs_arc_shrinker_limit != 0 ? 202 zfs_arc_shrinker_limit : INT64_MAX; 203 return (MIN(limit, btop((int64_t)arc_evictable_memory()))); 204 } 205 206 static unsigned long 207 arc_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc) 208 { 209 ASSERT((sc->gfp_mask & __GFP_FS) != 0); 210 211 /* The arc is considered warm once reclaim has occurred */ 212 if (unlikely(arc_warm == B_FALSE)) 213 arc_warm = B_TRUE; 214 215 /* 216 * Evict the requested number of pages by reducing arc_c and waiting 217 * for the requested amount of data to be evicted. 218 */ 219 arc_reduce_target_size(ptob(sc->nr_to_scan)); 220 arc_wait_for_eviction(ptob(sc->nr_to_scan), B_FALSE); 221 if (current->reclaim_state != NULL) 222 current->reclaim_state->reclaimed_slab += sc->nr_to_scan; 223 224 /* 225 * We are experiencing memory pressure which the arc_evict_zthr was 226 * unable to keep up with. Set arc_no_grow to briefly pause arc 227 * growth to avoid compounding the memory pressure. 228 */ 229 arc_no_grow = B_TRUE; 230 231 /* 232 * When direct reclaim is observed it usually indicates a rapid 233 * increase in memory pressure. This occurs because the kswapd 234 * threads were unable to asynchronously keep enough free memory 235 * available. 236 */ 237 if (current_is_kswapd()) { 238 ARCSTAT_BUMP(arcstat_memory_indirect_count); 239 } else { 240 ARCSTAT_BUMP(arcstat_memory_direct_count); 241 } 242 243 return (sc->nr_to_scan); 244 } 245 246 SPL_SHRINKER_DECLARE(arc_shrinker, 247 arc_shrinker_count, arc_shrinker_scan, DEFAULT_SEEKS); 248 249 int 250 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) 251 { 252 uint64_t free_memory = arc_free_memory(); 253 254 if (free_memory > arc_all_memory() * arc_lotsfree_percent / 100) 255 return (0); 256 257 if (txg > spa->spa_lowmem_last_txg) { 258 spa->spa_lowmem_last_txg = txg; 259 spa->spa_lowmem_page_load = 0; 260 } 261 /* 262 * If we are in pageout, we know that memory is already tight, 263 * the arc is already going to be evicting, so we just want to 264 * continue to let page writes occur as quickly as possible. 265 */ 266 if (current_is_kswapd()) { 267 if (spa->spa_lowmem_page_load > 268 MAX(arc_sys_free / 4, free_memory) / 4) { 269 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim); 270 return (SET_ERROR(ERESTART)); 271 } 272 /* Note: reserve is inflated, so we deflate */ 273 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8); 274 return (0); 275 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) { 276 /* memory is low, delay before restarting */ 277 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 278 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim); 279 return (SET_ERROR(EAGAIN)); 280 } 281 spa->spa_lowmem_page_load = 0; 282 return (0); 283 } 284 285 static void 286 arc_set_sys_free(uint64_t allmem) 287 { 288 /* 289 * The ARC tries to keep at least this much memory available for the 290 * system. This gives the ARC time to shrink in response to memory 291 * pressure, before running completely out of memory and invoking the 292 * direct-reclaim ARC shrinker. 293 * 294 * This should be more than twice high_wmark_pages(), so that 295 * arc_wait_for_eviction() will wait until at least the 296 * high_wmark_pages() are free (see arc_evict_state_impl()). 297 * 298 * Note: Even when the system is very low on memory, the kernel's 299 * shrinker code may only ask for one "batch" of pages (512KB) to be 300 * evicted. If concurrent allocations consume these pages, there may 301 * still be insufficient free pages, and the OOM killer takes action. 302 * 303 * By setting arc_sys_free large enough, and having 304 * arc_wait_for_eviction() wait until there is at least arc_sys_free/2 305 * free memory, it is much less likely that concurrent allocations can 306 * consume all the memory that was evicted before checking for 307 * OOM. 308 * 309 * It's hard to iterate the zones from a linux kernel module, which 310 * makes it difficult to determine the watermark dynamically. Instead 311 * we compute the maximum high watermark for this system, based 312 * on the amount of memory, assuming default parameters on Linux kernel 313 * 5.3. 314 */ 315 316 /* 317 * Base wmark_low is 4 * the square root of Kbytes of RAM. 318 */ 319 long wmark = 4 * int_sqrt(allmem/1024) * 1024; 320 321 /* 322 * Clamp to between 128K and 64MB. 323 */ 324 wmark = MAX(wmark, 128 * 1024); 325 wmark = MIN(wmark, 64 * 1024 * 1024); 326 327 /* 328 * watermark_boost can increase the wmark by up to 150%. 329 */ 330 wmark += wmark * 150 / 100; 331 332 /* 333 * arc_sys_free needs to be more than 2x the watermark, because 334 * arc_wait_for_eviction() waits for half of arc_sys_free. Bump this up 335 * to 3x to ensure we're above it. 336 */ 337 arc_sys_free = wmark * 3 + allmem / 32; 338 } 339 340 void 341 arc_lowmem_init(void) 342 { 343 uint64_t allmem = arc_all_memory(); 344 345 /* 346 * Register a shrinker to support synchronous (direct) memory 347 * reclaim from the arc. This is done to prevent kswapd from 348 * swapping out pages when it is preferable to shrink the arc. 349 */ 350 spl_register_shrinker(&arc_shrinker); 351 arc_set_sys_free(allmem); 352 } 353 354 void 355 arc_lowmem_fini(void) 356 { 357 spl_unregister_shrinker(&arc_shrinker); 358 } 359 360 int 361 param_set_arc_u64(const char *buf, zfs_kernel_param_t *kp) 362 { 363 int error; 364 365 error = spl_param_set_u64(buf, kp); 366 if (error < 0) 367 return (SET_ERROR(error)); 368 369 arc_tuning_update(B_TRUE); 370 371 return (0); 372 } 373 374 int 375 param_set_arc_min(const char *buf, zfs_kernel_param_t *kp) 376 { 377 return (param_set_arc_u64(buf, kp)); 378 } 379 380 int 381 param_set_arc_max(const char *buf, zfs_kernel_param_t *kp) 382 { 383 return (param_set_arc_u64(buf, kp)); 384 } 385 386 int 387 param_set_arc_int(const char *buf, zfs_kernel_param_t *kp) 388 { 389 int error; 390 391 error = param_set_int(buf, kp); 392 if (error < 0) 393 return (SET_ERROR(error)); 394 395 arc_tuning_update(B_TRUE); 396 397 return (0); 398 } 399 400 #ifdef CONFIG_MEMORY_HOTPLUG 401 static int 402 arc_hotplug_callback(struct notifier_block *self, unsigned long action, 403 void *arg) 404 { 405 (void) self, (void) arg; 406 uint64_t allmem = arc_all_memory(); 407 if (action != MEM_ONLINE) 408 return (NOTIFY_OK); 409 410 arc_set_limits(allmem); 411 412 #ifdef __LP64__ 413 if (zfs_dirty_data_max_max == 0) 414 zfs_dirty_data_max_max = MIN(4ULL * 1024 * 1024 * 1024, 415 allmem * zfs_dirty_data_max_max_percent / 100); 416 #else 417 if (zfs_dirty_data_max_max == 0) 418 zfs_dirty_data_max_max = MIN(1ULL * 1024 * 1024 * 1024, 419 allmem * zfs_dirty_data_max_max_percent / 100); 420 #endif 421 422 arc_set_sys_free(allmem); 423 return (NOTIFY_OK); 424 } 425 #endif 426 427 void 428 arc_register_hotplug(void) 429 { 430 #ifdef CONFIG_MEMORY_HOTPLUG 431 arc_hotplug_callback_mem_nb.notifier_call = arc_hotplug_callback; 432 /* There is no significance to the value 100 */ 433 arc_hotplug_callback_mem_nb.priority = 100; 434 register_memory_notifier(&arc_hotplug_callback_mem_nb); 435 #endif 436 } 437 438 void 439 arc_unregister_hotplug(void) 440 { 441 #ifdef CONFIG_MEMORY_HOTPLUG 442 unregister_memory_notifier(&arc_hotplug_callback_mem_nb); 443 #endif 444 } 445 #else /* _KERNEL */ 446 int64_t 447 arc_available_memory(void) 448 { 449 int64_t lowest = INT64_MAX; 450 451 /* Every 100 calls, free a small amount */ 452 if (random_in_range(100) == 0) 453 lowest = -1024; 454 455 return (lowest); 456 } 457 458 int 459 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) 460 { 461 (void) spa, (void) reserve, (void) txg; 462 return (0); 463 } 464 465 uint64_t 466 arc_all_memory(void) 467 { 468 return (ptob(physmem) / 2); 469 } 470 471 uint64_t 472 arc_free_memory(void) 473 { 474 return (random_in_range(arc_all_memory() * 20 / 100)); 475 } 476 477 void 478 arc_register_hotplug(void) 479 { 480 } 481 482 void 483 arc_unregister_hotplug(void) 484 { 485 } 486 #endif /* _KERNEL */ 487 488 /* 489 * Helper function for arc_prune_async() it is responsible for safely 490 * handling the execution of a registered arc_prune_func_t. 491 */ 492 static void 493 arc_prune_task(void *ptr) 494 { 495 arc_prune_t *ap = (arc_prune_t *)ptr; 496 arc_prune_func_t *func = ap->p_pfunc; 497 498 if (func != NULL) 499 func(ap->p_adjust, ap->p_private); 500 501 zfs_refcount_remove(&ap->p_refcnt, func); 502 } 503 504 /* 505 * Notify registered consumers they must drop holds on a portion of the ARC 506 * buffered they reference. This provides a mechanism to ensure the ARC can 507 * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers. This 508 * is analogous to dnlc_reduce_cache() but more generic. 509 * 510 * This operation is performed asynchronously so it may be safely called 511 * in the context of the arc_reclaim_thread(). A reference is taken here 512 * for each registered arc_prune_t and the arc_prune_task() is responsible 513 * for releasing it once the registered arc_prune_func_t has completed. 514 */ 515 void 516 arc_prune_async(uint64_t adjust) 517 { 518 arc_prune_t *ap; 519 520 mutex_enter(&arc_prune_mtx); 521 for (ap = list_head(&arc_prune_list); ap != NULL; 522 ap = list_next(&arc_prune_list, ap)) { 523 524 if (zfs_refcount_count(&ap->p_refcnt) >= 2) 525 continue; 526 527 zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc); 528 ap->p_adjust = adjust; 529 if (taskq_dispatch(arc_prune_taskq, arc_prune_task, 530 ap, TQ_SLEEP) == TASKQID_INVALID) { 531 zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc); 532 continue; 533 } 534 ARCSTAT_BUMP(arcstat_prune); 535 } 536 mutex_exit(&arc_prune_mtx); 537 } 538 539 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, shrinker_limit, INT, ZMOD_RW, 540 "Limit on number of pages that ARC shrinker can reclaim at once"); 541