1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * DAMON-based page reclamation 4 * 5 * Author: SeongJae Park <sj@kernel.org> 6 */ 7 8 #define pr_fmt(fmt) "damon-reclaim: " fmt 9 10 #include <linux/damon.h> 11 #include <linux/ioport.h> 12 #include <linux/module.h> 13 #include <linux/sched.h> 14 #include <linux/workqueue.h> 15 16 #ifdef MODULE_PARAM_PREFIX 17 #undef MODULE_PARAM_PREFIX 18 #endif 19 #define MODULE_PARAM_PREFIX "damon_reclaim." 20 21 /* 22 * Enable or disable DAMON_RECLAIM. 23 * 24 * You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``. 25 * Setting it as ``N`` disables DAMON_RECLAIM. Note that DAMON_RECLAIM could 26 * do no real monitoring and reclamation due to the watermarks-based activation 27 * condition. Refer to below descriptions for the watermarks parameter for 28 * this. 29 */ 30 static bool enabled __read_mostly; 31 32 /* 33 * Make DAMON_RECLAIM reads the input parameters again, except ``enabled``. 34 * 35 * Input parameters that updated while DAMON_RECLAIM is running are not applied 36 * by default. Once this parameter is set as ``Y``, DAMON_RECLAIM reads values 37 * of parametrs except ``enabled`` again. Once the re-reading is done, this 38 * parameter is set as ``N``. If invalid parameters are found while the 39 * re-reading, DAMON_RECLAIM will be disabled. 40 */ 41 static bool commit_inputs __read_mostly; 42 module_param(commit_inputs, bool, 0600); 43 44 /* 45 * Time threshold for cold memory regions identification in microseconds. 46 * 47 * If a memory region is not accessed for this or longer time, DAMON_RECLAIM 48 * identifies the region as cold, and reclaims. 120 seconds by default. 49 */ 50 static unsigned long min_age __read_mostly = 120000000; 51 module_param(min_age, ulong, 0600); 52 53 /* 54 * Limit of time for trying the reclamation in milliseconds. 55 * 56 * DAMON_RECLAIM tries to use only up to this time within a time window 57 * (quota_reset_interval_ms) for trying reclamation of cold pages. This can be 58 * used for limiting CPU consumption of DAMON_RECLAIM. If the value is zero, 59 * the limit is disabled. 60 * 61 * 10 ms by default. 62 */ 63 static unsigned long quota_ms __read_mostly = 10; 64 module_param(quota_ms, ulong, 0600); 65 66 /* 67 * Limit of size of memory for the reclamation in bytes. 68 * 69 * DAMON_RECLAIM charges amount of memory which it tried to reclaim within a 70 * time window (quota_reset_interval_ms) and makes no more than this limit is 71 * tried. This can be used for limiting consumption of CPU and IO. If this 72 * value is zero, the limit is disabled. 73 * 74 * 128 MiB by default. 75 */ 76 static unsigned long quota_sz __read_mostly = 128 * 1024 * 1024; 77 module_param(quota_sz, ulong, 0600); 78 79 /* 80 * The time/size quota charge reset interval in milliseconds. 81 * 82 * The charge reset interval for the quota of time (quota_ms) and size 83 * (quota_sz). That is, DAMON_RECLAIM does not try reclamation for more than 84 * quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms 85 * milliseconds. 86 * 87 * 1 second by default. 88 */ 89 static unsigned long quota_reset_interval_ms __read_mostly = 1000; 90 module_param(quota_reset_interval_ms, ulong, 0600); 91 92 /* 93 * The watermarks check time interval in microseconds. 94 * 95 * Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is 96 * enabled but inactive due to its watermarks rule. 5 seconds by default. 97 */ 98 static unsigned long wmarks_interval __read_mostly = 5000000; 99 module_param(wmarks_interval, ulong, 0600); 100 101 /* 102 * Free memory rate (per thousand) for the high watermark. 103 * 104 * If free memory of the system in bytes per thousand bytes is higher than 105 * this, DAMON_RECLAIM becomes inactive, so it does nothing but periodically 106 * checks the watermarks. 500 (50%) by default. 107 */ 108 static unsigned long wmarks_high __read_mostly = 500; 109 module_param(wmarks_high, ulong, 0600); 110 111 /* 112 * Free memory rate (per thousand) for the middle watermark. 113 * 114 * If free memory of the system in bytes per thousand bytes is between this and 115 * the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring 116 * and the reclaiming. 400 (40%) by default. 117 */ 118 static unsigned long wmarks_mid __read_mostly = 400; 119 module_param(wmarks_mid, ulong, 0600); 120 121 /* 122 * Free memory rate (per thousand) for the low watermark. 123 * 124 * If free memory of the system in bytes per thousand bytes is lower than this, 125 * DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks 126 * the watermarks. In the case, the system falls back to the LRU-based page 127 * granularity reclamation logic. 200 (20%) by default. 128 */ 129 static unsigned long wmarks_low __read_mostly = 200; 130 module_param(wmarks_low, ulong, 0600); 131 132 /* 133 * Sampling interval for the monitoring in microseconds. 134 * 135 * The sampling interval of DAMON for the cold memory monitoring. Please refer 136 * to the DAMON documentation for more detail. 5 ms by default. 137 */ 138 static unsigned long sample_interval __read_mostly = 5000; 139 module_param(sample_interval, ulong, 0600); 140 141 /* 142 * Aggregation interval for the monitoring in microseconds. 143 * 144 * The aggregation interval of DAMON for the cold memory monitoring. Please 145 * refer to the DAMON documentation for more detail. 100 ms by default. 146 */ 147 static unsigned long aggr_interval __read_mostly = 100000; 148 module_param(aggr_interval, ulong, 0600); 149 150 /* 151 * Minimum number of monitoring regions. 152 * 153 * The minimal number of monitoring regions of DAMON for the cold memory 154 * monitoring. This can be used to set lower-bound of the monitoring quality. 155 * But, setting this too high could result in increased monitoring overhead. 156 * Please refer to the DAMON documentation for more detail. 10 by default. 157 */ 158 static unsigned long min_nr_regions __read_mostly = 10; 159 module_param(min_nr_regions, ulong, 0600); 160 161 /* 162 * Maximum number of monitoring regions. 163 * 164 * The maximum number of monitoring regions of DAMON for the cold memory 165 * monitoring. This can be used to set upper-bound of the monitoring overhead. 166 * However, setting this too low could result in bad monitoring quality. 167 * Please refer to the DAMON documentation for more detail. 1000 by default. 168 */ 169 static unsigned long max_nr_regions __read_mostly = 1000; 170 module_param(max_nr_regions, ulong, 0600); 171 172 /* 173 * Start of the target memory region in physical address. 174 * 175 * The start physical address of memory region that DAMON_RECLAIM will do work 176 * against. By default, biggest System RAM is used as the region. 177 */ 178 static unsigned long monitor_region_start __read_mostly; 179 module_param(monitor_region_start, ulong, 0600); 180 181 /* 182 * End of the target memory region in physical address. 183 * 184 * The end physical address of memory region that DAMON_RECLAIM will do work 185 * against. By default, biggest System RAM is used as the region. 186 */ 187 static unsigned long monitor_region_end __read_mostly; 188 module_param(monitor_region_end, ulong, 0600); 189 190 /* 191 * PID of the DAMON thread 192 * 193 * If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread. 194 * Else, -1. 195 */ 196 static int kdamond_pid __read_mostly = -1; 197 module_param(kdamond_pid, int, 0400); 198 199 /* 200 * Number of memory regions that tried to be reclaimed. 201 */ 202 static unsigned long nr_reclaim_tried_regions __read_mostly; 203 module_param(nr_reclaim_tried_regions, ulong, 0400); 204 205 /* 206 * Total bytes of memory regions that tried to be reclaimed. 207 */ 208 static unsigned long bytes_reclaim_tried_regions __read_mostly; 209 module_param(bytes_reclaim_tried_regions, ulong, 0400); 210 211 /* 212 * Number of memory regions that successfully be reclaimed. 213 */ 214 static unsigned long nr_reclaimed_regions __read_mostly; 215 module_param(nr_reclaimed_regions, ulong, 0400); 216 217 /* 218 * Total bytes of memory regions that successfully be reclaimed. 219 */ 220 static unsigned long bytes_reclaimed_regions __read_mostly; 221 module_param(bytes_reclaimed_regions, ulong, 0400); 222 223 /* 224 * Number of times that the time/space quota limits have exceeded 225 */ 226 static unsigned long nr_quota_exceeds __read_mostly; 227 module_param(nr_quota_exceeds, ulong, 0400); 228 229 static struct damon_ctx *ctx; 230 static struct damon_target *target; 231 232 struct damon_reclaim_ram_walk_arg { 233 unsigned long start; 234 unsigned long end; 235 }; 236 237 static int walk_system_ram(struct resource *res, void *arg) 238 { 239 struct damon_reclaim_ram_walk_arg *a = arg; 240 241 if (a->end - a->start < resource_size(res)) { 242 a->start = res->start; 243 a->end = res->end; 244 } 245 return 0; 246 } 247 248 /* 249 * Find biggest 'System RAM' resource and store its start and end address in 250 * @start and @end, respectively. If no System RAM is found, returns false. 251 */ 252 static bool get_monitoring_region(unsigned long *start, unsigned long *end) 253 { 254 struct damon_reclaim_ram_walk_arg arg = {}; 255 256 walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram); 257 if (arg.end <= arg.start) 258 return false; 259 260 *start = arg.start; 261 *end = arg.end; 262 return true; 263 } 264 265 static struct damos *damon_reclaim_new_scheme(void) 266 { 267 struct damos_watermarks wmarks = { 268 .metric = DAMOS_WMARK_FREE_MEM_RATE, 269 .interval = wmarks_interval, 270 .high = wmarks_high, 271 .mid = wmarks_mid, 272 .low = wmarks_low, 273 }; 274 struct damos_quota quota = { 275 /* 276 * Do not try reclamation for more than quota_ms milliseconds 277 * or quota_sz bytes within quota_reset_interval_ms. 278 */ 279 .ms = quota_ms, 280 .sz = quota_sz, 281 .reset_interval = quota_reset_interval_ms, 282 /* Within the quota, page out older regions first. */ 283 .weight_sz = 0, 284 .weight_nr_accesses = 0, 285 .weight_age = 1 286 }; 287 struct damos *scheme = damon_new_scheme( 288 /* Find regions having PAGE_SIZE or larger size */ 289 PAGE_SIZE, ULONG_MAX, 290 /* and not accessed at all */ 291 0, 0, 292 /* for min_age or more micro-seconds, and */ 293 min_age / aggr_interval, UINT_MAX, 294 /* page out those, as soon as found */ 295 DAMOS_PAGEOUT, 296 /* under the quota. */ 297 "a, 298 /* (De)activate this according to the watermarks. */ 299 &wmarks); 300 301 return scheme; 302 } 303 304 static int damon_reclaim_apply_parameters(void) 305 { 306 struct damos *scheme; 307 struct damon_addr_range addr_range; 308 int err = 0; 309 310 err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0, 311 min_nr_regions, max_nr_regions); 312 if (err) 313 return err; 314 315 /* Will be freed by next 'damon_set_schemes()' below */ 316 scheme = damon_reclaim_new_scheme(); 317 if (!scheme) 318 return -ENOMEM; 319 err = damon_set_schemes(ctx, &scheme, 1); 320 if (err) 321 return err; 322 323 if (monitor_region_start > monitor_region_end) 324 return -EINVAL; 325 if (!monitor_region_start && !monitor_region_end && 326 !get_monitoring_region(&monitor_region_start, 327 &monitor_region_end)) 328 return -EINVAL; 329 addr_range.start = monitor_region_start; 330 addr_range.end = monitor_region_end; 331 return damon_set_regions(target, &addr_range, 1); 332 } 333 334 static int damon_reclaim_turn(bool on) 335 { 336 int err; 337 338 if (!on) { 339 err = damon_stop(&ctx, 1); 340 if (!err) 341 kdamond_pid = -1; 342 return err; 343 } 344 345 err = damon_reclaim_apply_parameters(); 346 if (err) 347 return err; 348 349 err = damon_start(&ctx, 1, true); 350 if (err) 351 return err; 352 kdamond_pid = ctx->kdamond->pid; 353 return 0; 354 } 355 356 static struct delayed_work damon_reclaim_timer; 357 static void damon_reclaim_timer_fn(struct work_struct *work) 358 { 359 static bool last_enabled; 360 bool now_enabled; 361 362 now_enabled = enabled; 363 if (last_enabled != now_enabled) { 364 if (!damon_reclaim_turn(now_enabled)) 365 last_enabled = now_enabled; 366 else 367 enabled = last_enabled; 368 } 369 } 370 static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn); 371 372 static bool damon_reclaim_initialized; 373 374 static int damon_reclaim_enabled_store(const char *val, 375 const struct kernel_param *kp) 376 { 377 int rc = param_set_bool(val, kp); 378 379 if (rc < 0) 380 return rc; 381 382 /* system_wq might not initialized yet */ 383 if (!damon_reclaim_initialized) 384 return rc; 385 386 schedule_delayed_work(&damon_reclaim_timer, 0); 387 return 0; 388 } 389 390 static const struct kernel_param_ops enabled_param_ops = { 391 .set = damon_reclaim_enabled_store, 392 .get = param_get_bool, 393 }; 394 395 module_param_cb(enabled, &enabled_param_ops, &enabled, 0600); 396 MODULE_PARM_DESC(enabled, 397 "Enable or disable DAMON_RECLAIM (default: disabled)"); 398 399 static int damon_reclaim_handle_commit_inputs(void) 400 { 401 int err; 402 403 if (!commit_inputs) 404 return 0; 405 406 err = damon_reclaim_apply_parameters(); 407 commit_inputs = false; 408 return err; 409 } 410 411 static int damon_reclaim_after_aggregation(struct damon_ctx *c) 412 { 413 struct damos *s; 414 415 /* update the stats parameter */ 416 damon_for_each_scheme(s, c) { 417 nr_reclaim_tried_regions = s->stat.nr_tried; 418 bytes_reclaim_tried_regions = s->stat.sz_tried; 419 nr_reclaimed_regions = s->stat.nr_applied; 420 bytes_reclaimed_regions = s->stat.sz_applied; 421 nr_quota_exceeds = s->stat.qt_exceeds; 422 } 423 424 return damon_reclaim_handle_commit_inputs(); 425 } 426 427 static int damon_reclaim_after_wmarks_check(struct damon_ctx *c) 428 { 429 return damon_reclaim_handle_commit_inputs(); 430 } 431 432 static int __init damon_reclaim_init(void) 433 { 434 ctx = damon_new_ctx(); 435 if (!ctx) 436 return -ENOMEM; 437 438 if (damon_select_ops(ctx, DAMON_OPS_PADDR)) { 439 damon_destroy_ctx(ctx); 440 return -EINVAL; 441 } 442 443 ctx->callback.after_wmarks_check = damon_reclaim_after_wmarks_check; 444 ctx->callback.after_aggregation = damon_reclaim_after_aggregation; 445 446 target = damon_new_target(); 447 if (!target) { 448 damon_destroy_ctx(ctx); 449 return -ENOMEM; 450 } 451 damon_add_target(ctx, target); 452 453 schedule_delayed_work(&damon_reclaim_timer, 0); 454 455 damon_reclaim_initialized = true; 456 return 0; 457 } 458 459 module_init(damon_reclaim_init); 460