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 * This may be overridden by tuning the zfs_arc_max module parameter. 84 */ 85 uint64_t 86 arc_default_max(uint64_t min, uint64_t allmem) 87 { 88 uint64_t size; 89 90 if (allmem >= 1 << 30) 91 size = allmem - (1 << 30); 92 else 93 size = min; 94 return (MAX(allmem * 5 / 8, size)); 95 } 96 97 #ifdef _KERNEL 98 /* 99 * Return maximum amount of memory that we could possibly use. Reduced 100 * to half of all memory in user space which is primarily used for testing. 101 */ 102 uint64_t 103 arc_all_memory(void) 104 { 105 #ifdef CONFIG_HIGHMEM 106 return (ptob(zfs_totalram_pages - zfs_totalhigh_pages)); 107 #else 108 return (ptob(zfs_totalram_pages)); 109 #endif /* CONFIG_HIGHMEM */ 110 } 111 112 /* 113 * Return the amount of memory that is considered free. In user space 114 * which is primarily used for testing we pretend that free memory ranges 115 * from 0-20% of all memory. 116 */ 117 uint64_t 118 arc_free_memory(void) 119 { 120 #ifdef CONFIG_HIGHMEM 121 struct sysinfo si; 122 si_meminfo(&si); 123 return (ptob(si.freeram - si.freehigh)); 124 #else 125 return (ptob(nr_free_pages() + 126 nr_inactive_file_pages())); 127 #endif /* CONFIG_HIGHMEM */ 128 } 129 130 /* 131 * Return the amount of memory that can be consumed before reclaim will be 132 * needed. Positive if there is sufficient free memory, negative indicates 133 * the amount of memory that needs to be freed up. 134 */ 135 int64_t 136 arc_available_memory(void) 137 { 138 return (arc_free_memory() - arc_sys_free); 139 } 140 141 static uint64_t 142 arc_evictable_memory(void) 143 { 144 int64_t asize = aggsum_value(&arc_sums.arcstat_size); 145 uint64_t arc_clean = 146 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_DATA]) + 147 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_METADATA]) + 148 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_DATA]) + 149 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 150 uint64_t arc_dirty = MAX((int64_t)asize - (int64_t)arc_clean, 0); 151 152 /* 153 * Scale reported evictable memory in proportion to page cache, cap 154 * at specified min/max. 155 */ 156 uint64_t min = (ptob(nr_file_pages()) / 100) * zfs_arc_pc_percent; 157 min = MAX(arc_c_min, MIN(arc_c_max, min)); 158 159 if (arc_dirty >= min) 160 return (arc_clean); 161 162 return (MAX((int64_t)asize - (int64_t)min, 0)); 163 } 164 165 /* 166 * The _count() function returns the number of free-able objects. 167 * The _scan() function returns the number of objects that were freed. 168 */ 169 static unsigned long 170 arc_shrinker_count(struct shrinker *shrink, struct shrink_control *sc) 171 { 172 /* 173 * __GFP_FS won't be set if we are called from ZFS code (see 174 * kmem_flags_convert(), which removes it). To avoid a deadlock, we 175 * don't allow evicting in this case. We return 0 rather than 176 * SHRINK_STOP so that the shrinker logic doesn't accumulate a 177 * deficit against us. 178 */ 179 if (!(sc->gfp_mask & __GFP_FS)) { 180 return (0); 181 } 182 183 /* 184 * This code is reached in the "direct reclaim" case, where the 185 * kernel (outside ZFS) is trying to allocate a page, and the system 186 * is low on memory. 187 * 188 * The kernel's shrinker code doesn't understand how many pages the 189 * ARC's callback actually frees, so it may ask the ARC to shrink a 190 * lot for one page allocation. This is problematic because it may 191 * take a long time, thus delaying the page allocation, and because 192 * it may force the ARC to unnecessarily shrink very small. 193 * 194 * Therefore, we limit the amount of data that we say is evictable, 195 * which limits the amount that the shrinker will ask us to evict for 196 * one page allocation attempt. 197 * 198 * In practice, we may be asked to shrink 4x the limit to satisfy one 199 * page allocation, before the kernel's shrinker code gives up on us. 200 * When that happens, we rely on the kernel code to find the pages 201 * that we freed before invoking the OOM killer. This happens in 202 * __alloc_pages_slowpath(), which retries and finds the pages we 203 * freed when it calls get_page_from_freelist(). 204 * 205 * See also the comment above zfs_arc_shrinker_limit. 206 */ 207 int64_t limit = zfs_arc_shrinker_limit != 0 ? 208 zfs_arc_shrinker_limit : INT64_MAX; 209 return (MIN(limit, btop((int64_t)arc_evictable_memory()))); 210 } 211 212 static unsigned long 213 arc_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc) 214 { 215 ASSERT((sc->gfp_mask & __GFP_FS) != 0); 216 217 /* The arc is considered warm once reclaim has occurred */ 218 if (unlikely(arc_warm == B_FALSE)) 219 arc_warm = B_TRUE; 220 221 /* 222 * Evict the requested number of pages by reducing arc_c and waiting 223 * for the requested amount of data to be evicted. 224 */ 225 arc_reduce_target_size(ptob(sc->nr_to_scan)); 226 arc_wait_for_eviction(ptob(sc->nr_to_scan), B_FALSE); 227 if (current->reclaim_state != NULL) 228 #ifdef HAVE_RECLAIM_STATE_RECLAIMED 229 current->reclaim_state->reclaimed += sc->nr_to_scan; 230 #else 231 current->reclaim_state->reclaimed_slab += sc->nr_to_scan; 232 #endif 233 234 /* 235 * We are experiencing memory pressure which the arc_evict_zthr was 236 * unable to keep up with. Set arc_no_grow to briefly pause arc 237 * growth to avoid compounding the memory pressure. 238 */ 239 arc_no_grow = B_TRUE; 240 241 /* 242 * When direct reclaim is observed it usually indicates a rapid 243 * increase in memory pressure. This occurs because the kswapd 244 * threads were unable to asynchronously keep enough free memory 245 * available. 246 */ 247 if (current_is_kswapd()) { 248 ARCSTAT_BUMP(arcstat_memory_indirect_count); 249 } else { 250 ARCSTAT_BUMP(arcstat_memory_direct_count); 251 } 252 253 return (sc->nr_to_scan); 254 } 255 256 static struct shrinker *arc_shrinker = NULL; 257 258 int 259 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) 260 { 261 uint64_t free_memory = arc_free_memory(); 262 263 if (free_memory > arc_all_memory() * arc_lotsfree_percent / 100) 264 return (0); 265 266 if (txg > spa->spa_lowmem_last_txg) { 267 spa->spa_lowmem_last_txg = txg; 268 spa->spa_lowmem_page_load = 0; 269 } 270 /* 271 * If we are in pageout, we know that memory is already tight, 272 * the arc is already going to be evicting, so we just want to 273 * continue to let page writes occur as quickly as possible. 274 */ 275 if (current_is_kswapd()) { 276 if (spa->spa_lowmem_page_load > 277 MAX(arc_sys_free / 4, free_memory) / 4) { 278 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim); 279 return (SET_ERROR(ERESTART)); 280 } 281 /* Note: reserve is inflated, so we deflate */ 282 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8); 283 return (0); 284 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) { 285 /* memory is low, delay before restarting */ 286 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 287 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim); 288 return (SET_ERROR(EAGAIN)); 289 } 290 spa->spa_lowmem_page_load = 0; 291 return (0); 292 } 293 294 static void 295 arc_set_sys_free(uint64_t allmem) 296 { 297 /* 298 * The ARC tries to keep at least this much memory available for the 299 * system. This gives the ARC time to shrink in response to memory 300 * pressure, before running completely out of memory and invoking the 301 * direct-reclaim ARC shrinker. 302 * 303 * This should be more than twice high_wmark_pages(), so that 304 * arc_wait_for_eviction() will wait until at least the 305 * high_wmark_pages() are free (see arc_evict_state_impl()). 306 * 307 * Note: Even when the system is very low on memory, the kernel's 308 * shrinker code may only ask for one "batch" of pages (512KB) to be 309 * evicted. If concurrent allocations consume these pages, there may 310 * still be insufficient free pages, and the OOM killer takes action. 311 * 312 * By setting arc_sys_free large enough, and having 313 * arc_wait_for_eviction() wait until there is at least arc_sys_free/2 314 * free memory, it is much less likely that concurrent allocations can 315 * consume all the memory that was evicted before checking for 316 * OOM. 317 * 318 * It's hard to iterate the zones from a linux kernel module, which 319 * makes it difficult to determine the watermark dynamically. Instead 320 * we compute the maximum high watermark for this system, based 321 * on the amount of memory, assuming default parameters on Linux kernel 322 * 5.3. 323 */ 324 325 /* 326 * Base wmark_low is 4 * the square root of Kbytes of RAM. 327 */ 328 long wmark = 4 * int_sqrt(allmem/1024) * 1024; 329 330 /* 331 * Clamp to between 128K and 64MB. 332 */ 333 wmark = MAX(wmark, 128 * 1024); 334 wmark = MIN(wmark, 64 * 1024 * 1024); 335 336 /* 337 * watermark_boost can increase the wmark by up to 150%. 338 */ 339 wmark += wmark * 150 / 100; 340 341 /* 342 * arc_sys_free needs to be more than 2x the watermark, because 343 * arc_wait_for_eviction() waits for half of arc_sys_free. Bump this up 344 * to 3x to ensure we're above it. 345 */ 346 arc_sys_free = wmark * 3 + allmem / 32; 347 } 348 349 void 350 arc_lowmem_init(void) 351 { 352 uint64_t allmem = arc_all_memory(); 353 354 /* 355 * Register a shrinker to support synchronous (direct) memory 356 * reclaim from the arc. This is done to prevent kswapd from 357 * swapping out pages when it is preferable to shrink the arc. 358 */ 359 arc_shrinker = spl_register_shrinker("zfs-arc-shrinker", 360 arc_shrinker_count, arc_shrinker_scan, DEFAULT_SEEKS); 361 VERIFY(arc_shrinker); 362 363 arc_set_sys_free(allmem); 364 } 365 366 void 367 arc_lowmem_fini(void) 368 { 369 spl_unregister_shrinker(arc_shrinker); 370 arc_shrinker = NULL; 371 } 372 373 int 374 param_set_arc_u64(const char *buf, zfs_kernel_param_t *kp) 375 { 376 int error; 377 378 error = spl_param_set_u64(buf, kp); 379 if (error < 0) 380 return (SET_ERROR(error)); 381 382 arc_tuning_update(B_TRUE); 383 384 return (0); 385 } 386 387 int 388 param_set_arc_min(const char *buf, zfs_kernel_param_t *kp) 389 { 390 return (param_set_arc_u64(buf, kp)); 391 } 392 393 int 394 param_set_arc_max(const char *buf, zfs_kernel_param_t *kp) 395 { 396 return (param_set_arc_u64(buf, kp)); 397 } 398 399 int 400 param_set_arc_int(const char *buf, zfs_kernel_param_t *kp) 401 { 402 int error; 403 404 error = param_set_int(buf, kp); 405 if (error < 0) 406 return (SET_ERROR(error)); 407 408 arc_tuning_update(B_TRUE); 409 410 return (0); 411 } 412 413 #ifdef CONFIG_MEMORY_HOTPLUG 414 static int 415 arc_hotplug_callback(struct notifier_block *self, unsigned long action, 416 void *arg) 417 { 418 (void) self, (void) arg; 419 uint64_t allmem = arc_all_memory(); 420 if (action != MEM_ONLINE) 421 return (NOTIFY_OK); 422 423 arc_set_limits(allmem); 424 425 #ifdef __LP64__ 426 if (zfs_dirty_data_max_max == 0) 427 zfs_dirty_data_max_max = MIN(4ULL * 1024 * 1024 * 1024, 428 allmem * zfs_dirty_data_max_max_percent / 100); 429 #else 430 if (zfs_dirty_data_max_max == 0) 431 zfs_dirty_data_max_max = MIN(1ULL * 1024 * 1024 * 1024, 432 allmem * zfs_dirty_data_max_max_percent / 100); 433 #endif 434 435 arc_set_sys_free(allmem); 436 return (NOTIFY_OK); 437 } 438 #endif 439 440 void 441 arc_register_hotplug(void) 442 { 443 #ifdef CONFIG_MEMORY_HOTPLUG 444 arc_hotplug_callback_mem_nb.notifier_call = arc_hotplug_callback; 445 /* There is no significance to the value 100 */ 446 arc_hotplug_callback_mem_nb.priority = 100; 447 register_memory_notifier(&arc_hotplug_callback_mem_nb); 448 #endif 449 } 450 451 void 452 arc_unregister_hotplug(void) 453 { 454 #ifdef CONFIG_MEMORY_HOTPLUG 455 unregister_memory_notifier(&arc_hotplug_callback_mem_nb); 456 #endif 457 } 458 #else /* _KERNEL */ 459 int64_t 460 arc_available_memory(void) 461 { 462 int64_t lowest = INT64_MAX; 463 464 /* Every 100 calls, free a small amount */ 465 if (random_in_range(100) == 0) 466 lowest = -1024; 467 468 return (lowest); 469 } 470 471 int 472 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) 473 { 474 (void) spa, (void) reserve, (void) txg; 475 return (0); 476 } 477 478 uint64_t 479 arc_all_memory(void) 480 { 481 return (ptob(physmem) / 2); 482 } 483 484 uint64_t 485 arc_free_memory(void) 486 { 487 return (random_in_range(arc_all_memory() * 20 / 100)); 488 } 489 490 void 491 arc_register_hotplug(void) 492 { 493 } 494 495 void 496 arc_unregister_hotplug(void) 497 { 498 } 499 #endif /* _KERNEL */ 500 501 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, shrinker_limit, INT, ZMOD_RW, 502 "Limit on number of pages that ARC shrinker can reclaim at once"); 503