root/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c

DEFINITIONS

1. shrinker_lock
2. shrinker_unlock
3. swap_available
4. can_release_pages
5. unsafe_drop_pages
6. try_to_writeback
7. i915_gem_shrink
8. i915_gem_shrink_all
9. i915_gem_shrinker_count
10. i915_gem_shrinker_scan
11. i915_gem_shrinker_oom
12. i915_gem_shrinker_vmap
13. i915_gem_driver_register__shrinker
14. i915_gem_driver_unregister__shrinker
15. i915_gem_shrinker_taints_mutex
16. i915_gem_object_make_unshrinkable
17. __i915_gem_object_make_shrinkable
18. i915_gem_object_make_shrinkable
19. i915_gem_object_make_purgeable

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2008-2015 Intel Corporation
   5  */
   6 
   7 #include <linux/oom.h>
   8 #include <linux/sched/mm.h>
   9 #include <linux/shmem_fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/swap.h>
  12 #include <linux/pci.h>
  13 #include <linux/dma-buf.h>
  14 #include <linux/vmalloc.h>
  15 #include <drm/i915_drm.h>
  16 
  17 #include "i915_trace.h"
  18 
  19 static bool shrinker_lock(struct drm_i915_private *i915,
  20                           unsigned int flags,
  21                           bool *unlock)
  22 {
  23         struct mutex *m = &i915->drm.struct_mutex;
  24 
  25         switch (mutex_trylock_recursive(m)) {
  26         case MUTEX_TRYLOCK_RECURSIVE:
  27                 *unlock = false;
  28                 return true;
  29 
  30         case MUTEX_TRYLOCK_FAILED:
  31                 *unlock = false;
  32                 if (flags & I915_SHRINK_ACTIVE &&
  33                     mutex_lock_killable_nested(m, I915_MM_SHRINKER) == 0)
  34                         *unlock = true;
  35                 return *unlock;
  36 
  37         case MUTEX_TRYLOCK_SUCCESS:
  38                 *unlock = true;
  39                 return true;
  40         }
  41 
  42         BUG();
  43 }
  44 
  45 static void shrinker_unlock(struct drm_i915_private *i915, bool unlock)
  46 {
  47         if (!unlock)
  48                 return;
  49 
  50         mutex_unlock(&i915->drm.struct_mutex);
  51 }
  52 
  53 static bool swap_available(void)
  54 {
  55         return get_nr_swap_pages() > 0;
  56 }
  57 
  58 static bool can_release_pages(struct drm_i915_gem_object *obj)
  59 {
  60         /* Consider only shrinkable ojects. */
  61         if (!i915_gem_object_is_shrinkable(obj))
  62                 return false;
  63 
  64         /* Only report true if by unbinding the object and putting its pages
  65          * we can actually make forward progress towards freeing physical
  66          * pages.
  67          *
  68          * If the pages are pinned for any other reason than being bound
  69          * to the GPU, simply unbinding from the GPU is not going to succeed
  70          * in releasing our pin count on the pages themselves.
  71          */
  72         if (atomic_read(&obj->mm.pages_pin_count) > atomic_read(&obj->bind_count))
  73                 return false;
  74 
  75         /* If any vma are "permanently" pinned, it will prevent us from
  76          * reclaiming the obj->mm.pages. We only allow scanout objects to claim
  77          * a permanent pin, along with a few others like the context objects.
  78          * To simplify the scan, and to avoid walking the list of vma under the
  79          * object, we just check the count of its permanently pinned.
  80          */
  81         if (READ_ONCE(obj->pin_global))
  82                 return false;
  83 
  84         /* We can only return physical pages to the system if we can either
  85          * discard the contents (because the user has marked them as being
  86          * purgeable) or if we can move their contents out to swap.
  87          */
  88         return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
  89 }
  90 
  91 static bool unsafe_drop_pages(struct drm_i915_gem_object *obj,
  92                               unsigned long shrink)
  93 {
  94         unsigned long flags;
  95 
  96         flags = 0;
  97         if (shrink & I915_SHRINK_ACTIVE)
  98                 flags = I915_GEM_OBJECT_UNBIND_ACTIVE;
  99 
 100         if (i915_gem_object_unbind(obj, flags) == 0)
 101                 __i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
 102 
 103         return !i915_gem_object_has_pages(obj);
 104 }
 105 
 106 static void try_to_writeback(struct drm_i915_gem_object *obj,
 107                              unsigned int flags)
 108 {
 109         switch (obj->mm.madv) {
 110         case I915_MADV_DONTNEED:
 111                 i915_gem_object_truncate(obj);
 112         case __I915_MADV_PURGED:
 113                 return;
 114         }
 115 
 116         if (flags & I915_SHRINK_WRITEBACK)
 117                 i915_gem_object_writeback(obj);
 118 }
 119 
 120 /**
 121  * i915_gem_shrink - Shrink buffer object caches
 122  * @i915: i915 device
 123  * @target: amount of memory to make available, in pages
 124  * @nr_scanned: optional output for number of pages scanned (incremental)
 125  * @shrink: control flags for selecting cache types
 126  *
 127  * This function is the main interface to the shrinker. It will try to release
 128  * up to @target pages of main memory backing storage from buffer objects.
 129  * Selection of the specific caches can be done with @flags. This is e.g. useful
 130  * when purgeable objects should be removed from caches preferentially.
 131  *
 132  * Note that it's not guaranteed that released amount is actually available as
 133  * free system memory - the pages might still be in-used to due to other reasons
 134  * (like cpu mmaps) or the mm core has reused them before we could grab them.
 135  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
 136  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
 137  *
 138  * Also note that any kind of pinning (both per-vma address space pins and
 139  * backing storage pins at the buffer object level) result in the shrinker code
 140  * having to skip the object.
 141  *
 142  * Returns:
 143  * The number of pages of backing storage actually released.
 144  */
 145 unsigned long
 146 i915_gem_shrink(struct drm_i915_private *i915,
 147                 unsigned long target,
 148                 unsigned long *nr_scanned,
 149                 unsigned int shrink)
 150 {
 151         const struct {
 152                 struct list_head *list;
 153                 unsigned int bit;
 154         } phases[] = {
 155                 { &i915->mm.purge_list, ~0u },
 156                 {
 157                         &i915->mm.shrink_list,
 158                         I915_SHRINK_BOUND | I915_SHRINK_UNBOUND
 159                 },
 160                 { NULL, 0 },
 161         }, *phase;
 162         intel_wakeref_t wakeref = 0;
 163         unsigned long count = 0;
 164         unsigned long scanned = 0;
 165         bool unlock;
 166 
 167         if (!shrinker_lock(i915, shrink, &unlock))
 168                 return 0;
 169 
 170         /*
 171          * When shrinking the active list, we should also consider active
 172          * contexts. Active contexts are pinned until they are retired, and
 173          * so can not be simply unbound to retire and unpin their pages. To
 174          * shrink the contexts, we must wait until the gpu is idle and
 175          * completed its switch to the kernel context. In short, we do
 176          * not have a good mechanism for idling a specific context.
 177          */
 178 
 179         trace_i915_gem_shrink(i915, target, shrink);
 180 
 181         /*
 182          * Unbinding of objects will require HW access; Let us not wake the
 183          * device just to recover a little memory. If absolutely necessary,
 184          * we will force the wake during oom-notifier.
 185          */
 186         if (shrink & I915_SHRINK_BOUND) {
 187                 wakeref = intel_runtime_pm_get_if_in_use(&i915->runtime_pm);
 188                 if (!wakeref)
 189                         shrink &= ~I915_SHRINK_BOUND;
 190         }
 191 
 192         /*
 193          * As we may completely rewrite the (un)bound list whilst unbinding
 194          * (due to retiring requests) we have to strictly process only
 195          * one element of the list at the time, and recheck the list
 196          * on every iteration.
 197          *
 198          * In particular, we must hold a reference whilst removing the
 199          * object as we may end up waiting for and/or retiring the objects.
 200          * This might release the final reference (held by the active list)
 201          * and result in the object being freed from under us. This is
 202          * similar to the precautions the eviction code must take whilst
 203          * removing objects.
 204          *
 205          * Also note that although these lists do not hold a reference to
 206          * the object we can safely grab one here: The final object
 207          * unreferencing and the bound_list are both protected by the
 208          * dev->struct_mutex and so we won't ever be able to observe an
 209          * object on the bound_list with a reference count equals 0.
 210          */
 211         for (phase = phases; phase->list; phase++) {
 212                 struct list_head still_in_list;
 213                 struct drm_i915_gem_object *obj;
 214                 unsigned long flags;
 215 
 216                 if ((shrink & phase->bit) == 0)
 217                         continue;
 218 
 219                 INIT_LIST_HEAD(&still_in_list);
 220 
 221                 /*
 222                  * We serialize our access to unreferenced objects through
 223                  * the use of the struct_mutex. While the objects are not
 224                  * yet freed (due to RCU then a workqueue) we still want
 225                  * to be able to shrink their pages, so they remain on
 226                  * the unbound/bound list until actually freed.
 227                  */
 228                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
 229                 while (count < target &&
 230                        (obj = list_first_entry_or_null(phase->list,
 231                                                        typeof(*obj),
 232                                                        mm.link))) {
 233                         list_move_tail(&obj->mm.link, &still_in_list);
 234 
 235                         if (shrink & I915_SHRINK_VMAPS &&
 236                             !is_vmalloc_addr(obj->mm.mapping))
 237                                 continue;
 238 
 239                         if (!(shrink & I915_SHRINK_ACTIVE) &&
 240                             i915_gem_object_is_framebuffer(obj))
 241                                 continue;
 242 
 243                         if (!(shrink & I915_SHRINK_BOUND) &&
 244                             atomic_read(&obj->bind_count))
 245                                 continue;
 246 
 247                         if (!can_release_pages(obj))
 248                                 continue;
 249 
 250                         if (!kref_get_unless_zero(&obj->base.refcount))
 251                                 continue;
 252 
 253                         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 254 
 255                         if (unsafe_drop_pages(obj, shrink)) {
 256                                 /* May arrive from get_pages on another bo */
 257                                 mutex_lock_nested(&obj->mm.lock,
 258                                                   I915_MM_SHRINKER);
 259                                 if (!i915_gem_object_has_pages(obj)) {
 260                                         try_to_writeback(obj, shrink);
 261                                         count += obj->base.size >> PAGE_SHIFT;
 262                                 }
 263                                 mutex_unlock(&obj->mm.lock);
 264                         }
 265 
 266                         scanned += obj->base.size >> PAGE_SHIFT;
 267                         i915_gem_object_put(obj);
 268 
 269                         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 270                 }
 271                 list_splice_tail(&still_in_list, phase->list);
 272                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 273         }
 274 
 275         if (shrink & I915_SHRINK_BOUND)
 276                 intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 277 
 278         shrinker_unlock(i915, unlock);
 279 
 280         if (nr_scanned)
 281                 *nr_scanned += scanned;
 282         return count;
 283 }
 284 
 285 /**
 286  * i915_gem_shrink_all - Shrink buffer object caches completely
 287  * @i915: i915 device
 288  *
 289  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
 290  * caches completely. It also first waits for and retires all outstanding
 291  * requests to also be able to release backing storage for active objects.
 292  *
 293  * This should only be used in code to intentionally quiescent the gpu or as a
 294  * last-ditch effort when memory seems to have run out.
 295  *
 296  * Returns:
 297  * The number of pages of backing storage actually released.
 298  */
 299 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915)
 300 {
 301         intel_wakeref_t wakeref;
 302         unsigned long freed = 0;
 303 
 304         with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 305                 freed = i915_gem_shrink(i915, -1UL, NULL,
 306                                         I915_SHRINK_BOUND |
 307                                         I915_SHRINK_UNBOUND |
 308                                         I915_SHRINK_ACTIVE);
 309         }
 310 
 311         return freed;
 312 }
 313 
 314 static unsigned long
 315 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 316 {
 317         struct drm_i915_private *i915 =
 318                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 319         unsigned long num_objects;
 320         unsigned long count;
 321 
 322         count = READ_ONCE(i915->mm.shrink_memory) >> PAGE_SHIFT;
 323         num_objects = READ_ONCE(i915->mm.shrink_count);
 324 
 325         /*
 326          * Update our preferred vmscan batch size for the next pass.
 327          * Our rough guess for an effective batch size is roughly 2
 328          * available GEM objects worth of pages. That is we don't want
 329          * the shrinker to fire, until it is worth the cost of freeing an
 330          * entire GEM object.
 331          */
 332         if (num_objects) {
 333                 unsigned long avg = 2 * count / num_objects;
 334 
 335                 i915->mm.shrinker.batch =
 336                         max((i915->mm.shrinker.batch + avg) >> 1,
 337                             128ul /* default SHRINK_BATCH */);
 338         }
 339 
 340         return count;
 341 }
 342 
 343 static unsigned long
 344 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 345 {
 346         struct drm_i915_private *i915 =
 347                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 348         unsigned long freed;
 349         bool unlock;
 350 
 351         sc->nr_scanned = 0;
 352 
 353         if (!shrinker_lock(i915, 0, &unlock))
 354                 return SHRINK_STOP;
 355 
 356         freed = i915_gem_shrink(i915,
 357                                 sc->nr_to_scan,
 358                                 &sc->nr_scanned,
 359                                 I915_SHRINK_BOUND |
 360                                 I915_SHRINK_UNBOUND |
 361                                 I915_SHRINK_WRITEBACK);
 362         if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
 363                 intel_wakeref_t wakeref;
 364 
 365                 with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 366                         freed += i915_gem_shrink(i915,
 367                                                  sc->nr_to_scan - sc->nr_scanned,
 368                                                  &sc->nr_scanned,
 369                                                  I915_SHRINK_ACTIVE |
 370                                                  I915_SHRINK_BOUND |
 371                                                  I915_SHRINK_UNBOUND |
 372                                                  I915_SHRINK_WRITEBACK);
 373                 }
 374         }
 375 
 376         shrinker_unlock(i915, unlock);
 377 
 378         return sc->nr_scanned ? freed : SHRINK_STOP;
 379 }
 380 
 381 static int
 382 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 383 {
 384         struct drm_i915_private *i915 =
 385                 container_of(nb, struct drm_i915_private, mm.oom_notifier);
 386         struct drm_i915_gem_object *obj;
 387         unsigned long unevictable, available, freed_pages;
 388         intel_wakeref_t wakeref;
 389         unsigned long flags;
 390 
 391         freed_pages = 0;
 392         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 393                 freed_pages += i915_gem_shrink(i915, -1UL, NULL,
 394                                                I915_SHRINK_BOUND |
 395                                                I915_SHRINK_UNBOUND |
 396                                                I915_SHRINK_WRITEBACK);
 397 
 398         /* Because we may be allocating inside our own driver, we cannot
 399          * assert that there are no objects with pinned pages that are not
 400          * being pointed to by hardware.
 401          */
 402         available = unevictable = 0;
 403         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 404         list_for_each_entry(obj, &i915->mm.shrink_list, mm.link) {
 405                 if (!can_release_pages(obj))
 406                         unevictable += obj->base.size >> PAGE_SHIFT;
 407                 else
 408                         available += obj->base.size >> PAGE_SHIFT;
 409         }
 410         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 411 
 412         if (freed_pages || available)
 413                 pr_info("Purging GPU memory, %lu pages freed, "
 414                         "%lu pages still pinned, %lu pages left available.\n",
 415                         freed_pages, unevictable, available);
 416 
 417         *(unsigned long *)ptr += freed_pages;
 418         return NOTIFY_DONE;
 419 }
 420 
 421 static int
 422 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 423 {
 424         struct drm_i915_private *i915 =
 425                 container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 426         struct i915_vma *vma, *next;
 427         unsigned long freed_pages = 0;
 428         intel_wakeref_t wakeref;
 429         bool unlock;
 430 
 431         if (!shrinker_lock(i915, 0, &unlock))
 432                 return NOTIFY_DONE;
 433 
 434         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 435                 freed_pages += i915_gem_shrink(i915, -1UL, NULL,
 436                                                I915_SHRINK_BOUND |
 437                                                I915_SHRINK_UNBOUND |
 438                                                I915_SHRINK_VMAPS);
 439 
 440         /* We also want to clear any cached iomaps as they wrap vmap */
 441         mutex_lock(&i915->ggtt.vm.mutex);
 442         list_for_each_entry_safe(vma, next,
 443                                  &i915->ggtt.vm.bound_list, vm_link) {
 444                 unsigned long count = vma->node.size >> PAGE_SHIFT;
 445 
 446                 if (!vma->iomap || i915_vma_is_active(vma))
 447                         continue;
 448 
 449                 mutex_unlock(&i915->ggtt.vm.mutex);
 450                 if (i915_vma_unbind(vma) == 0)
 451                         freed_pages += count;
 452                 mutex_lock(&i915->ggtt.vm.mutex);
 453         }
 454         mutex_unlock(&i915->ggtt.vm.mutex);
 455 
 456         shrinker_unlock(i915, unlock);
 457 
 458         *(unsigned long *)ptr += freed_pages;
 459         return NOTIFY_DONE;
 460 }
 461 
 462 void i915_gem_driver_register__shrinker(struct drm_i915_private *i915)
 463 {
 464         i915->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 465         i915->mm.shrinker.count_objects = i915_gem_shrinker_count;
 466         i915->mm.shrinker.seeks = DEFAULT_SEEKS;
 467         i915->mm.shrinker.batch = 4096;
 468         WARN_ON(register_shrinker(&i915->mm.shrinker));
 469 
 470         i915->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 471         WARN_ON(register_oom_notifier(&i915->mm.oom_notifier));
 472 
 473         i915->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
 474         WARN_ON(register_vmap_purge_notifier(&i915->mm.vmap_notifier));
 475 }
 476 
 477 void i915_gem_driver_unregister__shrinker(struct drm_i915_private *i915)
 478 {
 479         WARN_ON(unregister_vmap_purge_notifier(&i915->mm.vmap_notifier));
 480         WARN_ON(unregister_oom_notifier(&i915->mm.oom_notifier));
 481         unregister_shrinker(&i915->mm.shrinker);
 482 }
 483 
 484 void i915_gem_shrinker_taints_mutex(struct drm_i915_private *i915,
 485                                     struct mutex *mutex)
 486 {
 487         bool unlock = false;
 488 
 489         if (!IS_ENABLED(CONFIG_LOCKDEP))
 490                 return;
 491 
 492         if (!lockdep_is_held_type(&i915->drm.struct_mutex, -1)) {
 493                 mutex_acquire(&i915->drm.struct_mutex.dep_map,
 494                               I915_MM_NORMAL, 0, _RET_IP_);
 495                 unlock = true;
 496         }
 497 
 498         fs_reclaim_acquire(GFP_KERNEL);
 499 
 500         /*
 501          * As we invariably rely on the struct_mutex within the shrinker,
 502          * but have a complicated recursion dance, taint all the mutexes used
 503          * within the shrinker with the struct_mutex. For completeness, we
 504          * taint with all subclass of struct_mutex, even though we should
 505          * only need tainting by I915_MM_NORMAL to catch possible ABBA
 506          * deadlocks from using struct_mutex inside @mutex.
 507          */
 508         mutex_acquire(&i915->drm.struct_mutex.dep_map,
 509                       I915_MM_SHRINKER, 0, _RET_IP_);
 510 
 511         mutex_acquire(&mutex->dep_map, 0, 0, _RET_IP_);
 512         mutex_release(&mutex->dep_map, 0, _RET_IP_);
 513 
 514         mutex_release(&i915->drm.struct_mutex.dep_map, 0, _RET_IP_);
 515 
 516         fs_reclaim_release(GFP_KERNEL);
 517 
 518         if (unlock)
 519                 mutex_release(&i915->drm.struct_mutex.dep_map, 0, _RET_IP_);
 520 }
 521 
 522 #define obj_to_i915(obj__) to_i915((obj__)->base.dev)
 523 
 524 void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj)
 525 {
 526         /*
 527          * We can only be called while the pages are pinned or when
 528          * the pages are released. If pinned, we should only be called
 529          * from a single caller under controlled conditions; and on release
 530          * only one caller may release us. Neither the two may cross.
 531          */
 532         if (!list_empty(&obj->mm.link)) { /* pinned by caller */
 533                 struct drm_i915_private *i915 = obj_to_i915(obj);
 534                 unsigned long flags;
 535 
 536                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
 537                 GEM_BUG_ON(list_empty(&obj->mm.link));
 538 
 539                 list_del_init(&obj->mm.link);
 540                 i915->mm.shrink_count--;
 541                 i915->mm.shrink_memory -= obj->base.size;
 542 
 543                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 544         }
 545 }
 546 
 547 static void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj,
 548                                               struct list_head *head)
 549 {
 550         GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 551         GEM_BUG_ON(!list_empty(&obj->mm.link));
 552 
 553         if (i915_gem_object_is_shrinkable(obj)) {
 554                 struct drm_i915_private *i915 = obj_to_i915(obj);
 555                 unsigned long flags;
 556 
 557                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
 558                 GEM_BUG_ON(!kref_read(&obj->base.refcount));
 559 
 560                 list_add_tail(&obj->mm.link, head);
 561                 i915->mm.shrink_count++;
 562                 i915->mm.shrink_memory += obj->base.size;
 563 
 564                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 565         }
 566 }
 567 
 568 void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 569 {
 570         __i915_gem_object_make_shrinkable(obj,
 571                                           &obj_to_i915(obj)->mm.shrink_list);
 572 }
 573 
 574 void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 575 {
 576         __i915_gem_object_make_shrinkable(obj,
 577                                           &obj_to_i915(obj)->mm.purge_list);
 578 }