1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * DAMON api
4 *
5 * Author: SeongJae Park <sjpark@amazon.de>
6 */
7
8 #ifndef _DAMON_H_
9 #define _DAMON_H_
10
11 #include <linux/mutex.h>
12 #include <linux/time64.h>
13 #include <linux/types.h>
14 #include <linux/random.h>
15
16 /* Minimal region size. Every damon_region is aligned by this. */
17 #define DAMON_MIN_REGION PAGE_SIZE
18 /* Max priority score for DAMON-based operation schemes */
19 #define DAMOS_MAX_SCORE (99)
20
21 /* Get a random number in [l, r) */
damon_rand(unsigned long l,unsigned long r)22 static inline unsigned long damon_rand(unsigned long l, unsigned long r)
23 {
24 return l + prandom_u32_max(r - l);
25 }
26
27 /**
28 * struct damon_addr_range - Represents an address region of [@start, @end).
29 * @start: Start address of the region (inclusive).
30 * @end: End address of the region (exclusive).
31 */
32 struct damon_addr_range {
33 unsigned long start;
34 unsigned long end;
35 };
36
37 /**
38 * struct damon_region - Represents a monitoring target region.
39 * @ar: The address range of the region.
40 * @sampling_addr: Address of the sample for the next access check.
41 * @nr_accesses: Access frequency of this region.
42 * @list: List head for siblings.
43 * @age: Age of this region.
44 *
45 * @age is initially zero, increased for each aggregation interval, and reset
46 * to zero again if the access frequency is significantly changed. If two
47 * regions are merged into a new region, both @nr_accesses and @age of the new
48 * region are set as region size-weighted average of those of the two regions.
49 */
50 struct damon_region {
51 struct damon_addr_range ar;
52 unsigned long sampling_addr;
53 unsigned int nr_accesses;
54 struct list_head list;
55
56 unsigned int age;
57 /* private: Internal value for age calculation. */
58 unsigned int last_nr_accesses;
59 };
60
61 /**
62 * struct damon_target - Represents a monitoring target.
63 * @pid: The PID of the virtual address space to monitor.
64 * @nr_regions: Number of monitoring target regions of this target.
65 * @regions_list: Head of the monitoring target regions of this target.
66 * @list: List head for siblings.
67 *
68 * Each monitoring context could have multiple targets. For example, a context
69 * for virtual memory address spaces could have multiple target processes. The
70 * @pid should be set for appropriate &struct damon_operations including the
71 * virtual address spaces monitoring operations.
72 */
73 struct damon_target {
74 struct pid *pid;
75 unsigned int nr_regions;
76 struct list_head regions_list;
77 struct list_head list;
78 };
79
80 /**
81 * enum damos_action - Represents an action of a Data Access Monitoring-based
82 * Operation Scheme.
83 *
84 * @DAMOS_WILLNEED: Call ``madvise()`` for the region with MADV_WILLNEED.
85 * @DAMOS_COLD: Call ``madvise()`` for the region with MADV_COLD.
86 * @DAMOS_PAGEOUT: Call ``madvise()`` for the region with MADV_PAGEOUT.
87 * @DAMOS_HUGEPAGE: Call ``madvise()`` for the region with MADV_HUGEPAGE.
88 * @DAMOS_NOHUGEPAGE: Call ``madvise()`` for the region with MADV_NOHUGEPAGE.
89 * @DAMOS_STAT: Do nothing but count the stat.
90 * @NR_DAMOS_ACTIONS: Total number of DAMOS actions
91 */
92 enum damos_action {
93 DAMOS_WILLNEED,
94 DAMOS_COLD,
95 DAMOS_PAGEOUT,
96 DAMOS_HUGEPAGE,
97 DAMOS_NOHUGEPAGE,
98 DAMOS_STAT, /* Do nothing but only record the stat */
99 NR_DAMOS_ACTIONS,
100 };
101
102 /**
103 * struct damos_quota - Controls the aggressiveness of the given scheme.
104 * @ms: Maximum milliseconds that the scheme can use.
105 * @sz: Maximum bytes of memory that the action can be applied.
106 * @reset_interval: Charge reset interval in milliseconds.
107 *
108 * @weight_sz: Weight of the region's size for prioritization.
109 * @weight_nr_accesses: Weight of the region's nr_accesses for prioritization.
110 * @weight_age: Weight of the region's age for prioritization.
111 *
112 * To avoid consuming too much CPU time or IO resources for applying the
113 * &struct damos->action to large memory, DAMON allows users to set time and/or
114 * size quotas. The quotas can be set by writing non-zero values to &ms and
115 * &sz, respectively. If the time quota is set, DAMON tries to use only up to
116 * &ms milliseconds within &reset_interval for applying the action. If the
117 * size quota is set, DAMON tries to apply the action only up to &sz bytes
118 * within &reset_interval.
119 *
120 * Internally, the time quota is transformed to a size quota using estimated
121 * throughput of the scheme's action. DAMON then compares it against &sz and
122 * uses smaller one as the effective quota.
123 *
124 * For selecting regions within the quota, DAMON prioritizes current scheme's
125 * target memory regions using the &struct damon_operations->get_scheme_score.
126 * You could customize the prioritization logic by setting &weight_sz,
127 * &weight_nr_accesses, and &weight_age, because monitoring operations are
128 * encouraged to respect those.
129 */
130 struct damos_quota {
131 unsigned long ms;
132 unsigned long sz;
133 unsigned long reset_interval;
134
135 unsigned int weight_sz;
136 unsigned int weight_nr_accesses;
137 unsigned int weight_age;
138
139 /* private: */
140 /* For throughput estimation */
141 unsigned long total_charged_sz;
142 unsigned long total_charged_ns;
143
144 unsigned long esz; /* Effective size quota in bytes */
145
146 /* For charging the quota */
147 unsigned long charged_sz;
148 unsigned long charged_from;
149 struct damon_target *charge_target_from;
150 unsigned long charge_addr_from;
151
152 /* For prioritization */
153 unsigned long histogram[DAMOS_MAX_SCORE + 1];
154 unsigned int min_score;
155 };
156
157 /**
158 * enum damos_wmark_metric - Represents the watermark metric.
159 *
160 * @DAMOS_WMARK_NONE: Ignore the watermarks of the given scheme.
161 * @DAMOS_WMARK_FREE_MEM_RATE: Free memory rate of the system in [0,1000].
162 * @NR_DAMOS_WMARK_METRICS: Total number of DAMOS watermark metrics
163 */
164 enum damos_wmark_metric {
165 DAMOS_WMARK_NONE,
166 DAMOS_WMARK_FREE_MEM_RATE,
167 NR_DAMOS_WMARK_METRICS,
168 };
169
170 /**
171 * struct damos_watermarks - Controls when a given scheme should be activated.
172 * @metric: Metric for the watermarks.
173 * @interval: Watermarks check time interval in microseconds.
174 * @high: High watermark.
175 * @mid: Middle watermark.
176 * @low: Low watermark.
177 *
178 * If &metric is &DAMOS_WMARK_NONE, the scheme is always active. Being active
179 * means DAMON does monitoring and applying the action of the scheme to
180 * appropriate memory regions. Else, DAMON checks &metric of the system for at
181 * least every &interval microseconds and works as below.
182 *
183 * If &metric is higher than &high, the scheme is inactivated. If &metric is
184 * between &mid and &low, the scheme is activated. If &metric is lower than
185 * &low, the scheme is inactivated.
186 */
187 struct damos_watermarks {
188 enum damos_wmark_metric metric;
189 unsigned long interval;
190 unsigned long high;
191 unsigned long mid;
192 unsigned long low;
193
194 /* private: */
195 bool activated;
196 };
197
198 /**
199 * struct damos_stat - Statistics on a given scheme.
200 * @nr_tried: Total number of regions that the scheme is tried to be applied.
201 * @sz_tried: Total size of regions that the scheme is tried to be applied.
202 * @nr_applied: Total number of regions that the scheme is applied.
203 * @sz_applied: Total size of regions that the scheme is applied.
204 * @qt_exceeds: Total number of times the quota of the scheme has exceeded.
205 */
206 struct damos_stat {
207 unsigned long nr_tried;
208 unsigned long sz_tried;
209 unsigned long nr_applied;
210 unsigned long sz_applied;
211 unsigned long qt_exceeds;
212 };
213
214 /**
215 * struct damos - Represents a Data Access Monitoring-based Operation Scheme.
216 * @min_sz_region: Minimum size of target regions.
217 * @max_sz_region: Maximum size of target regions.
218 * @min_nr_accesses: Minimum ``->nr_accesses`` of target regions.
219 * @max_nr_accesses: Maximum ``->nr_accesses`` of target regions.
220 * @min_age_region: Minimum age of target regions.
221 * @max_age_region: Maximum age of target regions.
222 * @action: &damo_action to be applied to the target regions.
223 * @quota: Control the aggressiveness of this scheme.
224 * @wmarks: Watermarks for automated (in)activation of this scheme.
225 * @stat: Statistics of this scheme.
226 * @list: List head for siblings.
227 *
228 * For each aggregation interval, DAMON finds regions which fit in the
229 * condition (&min_sz_region, &max_sz_region, &min_nr_accesses,
230 * &max_nr_accesses, &min_age_region, &max_age_region) and applies &action to
231 * those. To avoid consuming too much CPU time or IO resources for the
232 * &action, "a is used.
233 *
234 * To do the work only when needed, schemes can be activated for specific
235 * system situations using &wmarks. If all schemes that registered to the
236 * monitoring context are inactive, DAMON stops monitoring either, and just
237 * repeatedly checks the watermarks.
238 *
239 * If all schemes that registered to a &struct damon_ctx are inactive, DAMON
240 * stops monitoring and just repeatedly checks the watermarks.
241 *
242 * After applying the &action to each region, &stat_count and &stat_sz is
243 * updated to reflect the number of regions and total size of regions that the
244 * &action is applied.
245 */
246 struct damos {
247 unsigned long min_sz_region;
248 unsigned long max_sz_region;
249 unsigned int min_nr_accesses;
250 unsigned int max_nr_accesses;
251 unsigned int min_age_region;
252 unsigned int max_age_region;
253 enum damos_action action;
254 struct damos_quota quota;
255 struct damos_watermarks wmarks;
256 struct damos_stat stat;
257 struct list_head list;
258 };
259
260 /**
261 * enum damon_ops_id - Identifier for each monitoring operations implementation
262 *
263 * @DAMON_OPS_VADDR: Monitoring operations for virtual address spaces
264 * @DAMON_OPS_FVADDR: Monitoring operations for only fixed ranges of virtual
265 * address spaces
266 * @DAMON_OPS_PADDR: Monitoring operations for the physical address space
267 * @NR_DAMON_OPS: Number of monitoring operations implementations
268 */
269 enum damon_ops_id {
270 DAMON_OPS_VADDR,
271 DAMON_OPS_FVADDR,
272 DAMON_OPS_PADDR,
273 NR_DAMON_OPS,
274 };
275
276 struct damon_ctx;
277
278 /**
279 * struct damon_operations - Monitoring operations for given use cases.
280 *
281 * @id: Identifier of this operations set.
282 * @init: Initialize operations-related data structures.
283 * @update: Update operations-related data structures.
284 * @prepare_access_checks: Prepare next access check of target regions.
285 * @check_accesses: Check the accesses to target regions.
286 * @reset_aggregated: Reset aggregated accesses monitoring results.
287 * @get_scheme_score: Get the score of a region for a scheme.
288 * @apply_scheme: Apply a DAMON-based operation scheme.
289 * @target_valid: Determine if the target is valid.
290 * @cleanup: Clean up the context.
291 *
292 * DAMON can be extended for various address spaces and usages. For this,
293 * users should register the low level operations for their target address
294 * space and usecase via the &damon_ctx.ops. Then, the monitoring thread
295 * (&damon_ctx.kdamond) calls @init and @prepare_access_checks before starting
296 * the monitoring, @update after each &damon_ctx.ops_update_interval, and
297 * @check_accesses, @target_valid and @prepare_access_checks after each
298 * &damon_ctx.sample_interval. Finally, @reset_aggregated is called after each
299 * &damon_ctx.aggr_interval.
300 *
301 * Each &struct damon_operations instance having valid @id can be registered
302 * via damon_register_ops() and selected by damon_select_ops() later.
303 * @init should initialize operations-related data structures. For example,
304 * this could be used to construct proper monitoring target regions and link
305 * those to @damon_ctx.adaptive_targets.
306 * @update should update the operations-related data structures. For example,
307 * this could be used to update monitoring target regions for current status.
308 * @prepare_access_checks should manipulate the monitoring regions to be
309 * prepared for the next access check.
310 * @check_accesses should check the accesses to each region that made after the
311 * last preparation and update the number of observed accesses of each region.
312 * It should also return max number of observed accesses that made as a result
313 * of its update. The value will be used for regions adjustment threshold.
314 * @reset_aggregated should reset the access monitoring results that aggregated
315 * by @check_accesses.
316 * @get_scheme_score should return the priority score of a region for a scheme
317 * as an integer in [0, &DAMOS_MAX_SCORE].
318 * @apply_scheme is called from @kdamond when a region for user provided
319 * DAMON-based operation scheme is found. It should apply the scheme's action
320 * to the region and return bytes of the region that the action is successfully
321 * applied.
322 * @target_valid should check whether the target is still valid for the
323 * monitoring.
324 * @cleanup is called from @kdamond just before its termination.
325 */
326 struct damon_operations {
327 enum damon_ops_id id;
328 void (*init)(struct damon_ctx *context);
329 void (*update)(struct damon_ctx *context);
330 void (*prepare_access_checks)(struct damon_ctx *context);
331 unsigned int (*check_accesses)(struct damon_ctx *context);
332 void (*reset_aggregated)(struct damon_ctx *context);
333 int (*get_scheme_score)(struct damon_ctx *context,
334 struct damon_target *t, struct damon_region *r,
335 struct damos *scheme);
336 unsigned long (*apply_scheme)(struct damon_ctx *context,
337 struct damon_target *t, struct damon_region *r,
338 struct damos *scheme);
339 bool (*target_valid)(void *target);
340 void (*cleanup)(struct damon_ctx *context);
341 };
342
343 /**
344 * struct damon_callback - Monitoring events notification callbacks.
345 *
346 * @before_start: Called before starting the monitoring.
347 * @after_wmarks_check: Called after each schemes' watermarks check.
348 * @after_sampling: Called after each sampling.
349 * @after_aggregation: Called after each aggregation.
350 * @before_terminate: Called before terminating the monitoring.
351 * @private: User private data.
352 *
353 * The monitoring thread (&damon_ctx.kdamond) calls @before_start and
354 * @before_terminate just before starting and finishing the monitoring,
355 * respectively. Therefore, those are good places for installing and cleaning
356 * @private.
357 *
358 * The monitoring thread calls @after_wmarks_check after each DAMON-based
359 * operation schemes' watermarks check. If users need to make changes to the
360 * attributes of the monitoring context while it's deactivated due to the
361 * watermarks, this is the good place to do.
362 *
363 * The monitoring thread calls @after_sampling and @after_aggregation for each
364 * of the sampling intervals and aggregation intervals, respectively.
365 * Therefore, users can safely access the monitoring results without additional
366 * protection. For the reason, users are recommended to use these callback for
367 * the accesses to the results.
368 *
369 * If any callback returns non-zero, monitoring stops.
370 */
371 struct damon_callback {
372 void *private;
373
374 int (*before_start)(struct damon_ctx *context);
375 int (*after_wmarks_check)(struct damon_ctx *context);
376 int (*after_sampling)(struct damon_ctx *context);
377 int (*after_aggregation)(struct damon_ctx *context);
378 void (*before_terminate)(struct damon_ctx *context);
379 };
380
381 /**
382 * struct damon_ctx - Represents a context for each monitoring. This is the
383 * main interface that allows users to set the attributes and get the results
384 * of the monitoring.
385 *
386 * @sample_interval: The time between access samplings.
387 * @aggr_interval: The time between monitor results aggregations.
388 * @ops_update_interval: The time between monitoring operations updates.
389 *
390 * For each @sample_interval, DAMON checks whether each region is accessed or
391 * not. It aggregates and keeps the access information (number of accesses to
392 * each region) for @aggr_interval time. DAMON also checks whether the target
393 * memory regions need update (e.g., by ``mmap()`` calls from the application,
394 * in case of virtual memory monitoring) and applies the changes for each
395 * @ops_update_interval. All time intervals are in micro-seconds.
396 * Please refer to &struct damon_operations and &struct damon_callback for more
397 * detail.
398 *
399 * @kdamond: Kernel thread who does the monitoring.
400 * @kdamond_stop: Notifies whether kdamond should stop.
401 * @kdamond_lock: Mutex for the synchronizations with @kdamond.
402 *
403 * For each monitoring context, one kernel thread for the monitoring is
404 * created. The pointer to the thread is stored in @kdamond.
405 *
406 * Once started, the monitoring thread runs until explicitly required to be
407 * terminated or every monitoring target is invalid. The validity of the
408 * targets is checked via the &damon_operations.target_valid of @ops. The
409 * termination can also be explicitly requested by writing non-zero to
410 * @kdamond_stop. The thread sets @kdamond to NULL when it terminates.
411 * Therefore, users can know whether the monitoring is ongoing or terminated by
412 * reading @kdamond. Reads and writes to @kdamond and @kdamond_stop from
413 * outside of the monitoring thread must be protected by @kdamond_lock.
414 *
415 * Note that the monitoring thread protects only @kdamond and @kdamond_stop via
416 * @kdamond_lock. Accesses to other fields must be protected by themselves.
417 *
418 * @ops: Set of monitoring operations for given use cases.
419 * @callback: Set of callbacks for monitoring events notifications.
420 *
421 * @min_nr_regions: The minimum number of adaptive monitoring regions.
422 * @max_nr_regions: The maximum number of adaptive monitoring regions.
423 * @adaptive_targets: Head of monitoring targets (&damon_target) list.
424 * @schemes: Head of schemes (&damos) list.
425 */
426 struct damon_ctx {
427 unsigned long sample_interval;
428 unsigned long aggr_interval;
429 unsigned long ops_update_interval;
430
431 /* private: internal use only */
432 struct timespec64 last_aggregation;
433 struct timespec64 last_ops_update;
434
435 /* public: */
436 struct task_struct *kdamond;
437 struct mutex kdamond_lock;
438
439 struct damon_operations ops;
440 struct damon_callback callback;
441
442 unsigned long min_nr_regions;
443 unsigned long max_nr_regions;
444 struct list_head adaptive_targets;
445 struct list_head schemes;
446 };
447
damon_next_region(struct damon_region * r)448 static inline struct damon_region *damon_next_region(struct damon_region *r)
449 {
450 return container_of(r->list.next, struct damon_region, list);
451 }
452
damon_prev_region(struct damon_region * r)453 static inline struct damon_region *damon_prev_region(struct damon_region *r)
454 {
455 return container_of(r->list.prev, struct damon_region, list);
456 }
457
damon_last_region(struct damon_target * t)458 static inline struct damon_region *damon_last_region(struct damon_target *t)
459 {
460 return list_last_entry(&t->regions_list, struct damon_region, list);
461 }
462
463 #define damon_for_each_region(r, t) \
464 list_for_each_entry(r, &t->regions_list, list)
465
466 #define damon_for_each_region_safe(r, next, t) \
467 list_for_each_entry_safe(r, next, &t->regions_list, list)
468
469 #define damon_for_each_target(t, ctx) \
470 list_for_each_entry(t, &(ctx)->adaptive_targets, list)
471
472 #define damon_for_each_target_safe(t, next, ctx) \
473 list_for_each_entry_safe(t, next, &(ctx)->adaptive_targets, list)
474
475 #define damon_for_each_scheme(s, ctx) \
476 list_for_each_entry(s, &(ctx)->schemes, list)
477
478 #define damon_for_each_scheme_safe(s, next, ctx) \
479 list_for_each_entry_safe(s, next, &(ctx)->schemes, list)
480
481 #ifdef CONFIG_DAMON
482
483 struct damon_region *damon_new_region(unsigned long start, unsigned long end);
484
485 /*
486 * Add a region between two other regions
487 */
damon_insert_region(struct damon_region * r,struct damon_region * prev,struct damon_region * next,struct damon_target * t)488 static inline void damon_insert_region(struct damon_region *r,
489 struct damon_region *prev, struct damon_region *next,
490 struct damon_target *t)
491 {
492 __list_add(&r->list, &prev->list, &next->list);
493 t->nr_regions++;
494 }
495
496 void damon_add_region(struct damon_region *r, struct damon_target *t);
497 void damon_destroy_region(struct damon_region *r, struct damon_target *t);
498 int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
499 unsigned int nr_ranges);
500
501 struct damos *damon_new_scheme(
502 unsigned long min_sz_region, unsigned long max_sz_region,
503 unsigned int min_nr_accesses, unsigned int max_nr_accesses,
504 unsigned int min_age_region, unsigned int max_age_region,
505 enum damos_action action, struct damos_quota *quota,
506 struct damos_watermarks *wmarks);
507 void damon_add_scheme(struct damon_ctx *ctx, struct damos *s);
508 void damon_destroy_scheme(struct damos *s);
509
510 struct damon_target *damon_new_target(void);
511 void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);
512 bool damon_targets_empty(struct damon_ctx *ctx);
513 void damon_free_target(struct damon_target *t);
514 void damon_destroy_target(struct damon_target *t);
515 unsigned int damon_nr_regions(struct damon_target *t);
516
517 struct damon_ctx *damon_new_ctx(void);
518 void damon_destroy_ctx(struct damon_ctx *ctx);
519 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
520 unsigned long aggr_int, unsigned long ops_upd_int,
521 unsigned long min_nr_reg, unsigned long max_nr_reg);
522 int damon_set_schemes(struct damon_ctx *ctx,
523 struct damos **schemes, ssize_t nr_schemes);
524 int damon_nr_running_ctxs(void);
525 bool damon_is_registered_ops(enum damon_ops_id id);
526 int damon_register_ops(struct damon_operations *ops);
527 int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id);
528
529 int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive);
530 int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
531
532 #endif /* CONFIG_DAMON */
533
534 #endif /* _DAMON_H */
535