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

   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
  16 #include "gt/intel_gt_requests.h"
  17
  18 #include "i915_trace.h"
  19
  20 static bool swap_available(void)
  21 {
  22         return get_nr_swap_pages() > 0;
  23 }
  24
  25 static bool can_release_pages(struct drm_i915_gem_object *obj)
  26 {
  27         /* Consider only shrinkable ojects. */
  28         if (!i915_gem_object_is_shrinkable(obj))
  29                 return false;
  30
  31         /*
  32          * We can only return physical pages to the system if we can either
  33          * discard the contents (because the user has marked them as being
  34          * purgeable) or if we can move their contents out to swap.
  35          */
  36         return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
  37 }
  38
  39 static bool drop_pages(struct drm_i915_gem_object *obj,
  40                        unsigned long shrink, bool trylock_vm)
  41 {
  42         unsigned long flags;
  43
  44         flags = 0;
  45         if (shrink & I915_SHRINK_ACTIVE)
  46                 flags |= I915_GEM_OBJECT_UNBIND_ACTIVE;
  47         if (!(shrink & I915_SHRINK_BOUND))
  48                 flags |= I915_GEM_OBJECT_UNBIND_TEST;
  49         if (trylock_vm)
  50                 flags |= I915_GEM_OBJECT_UNBIND_VM_TRYLOCK;
  51
  52         if (i915_gem_object_unbind(obj, flags) == 0)
  53                 return true;
  54
  55         return false;
  56 }
  57
  58 static int try_to_writeback(struct drm_i915_gem_object *obj, unsigned int flags)
  59 {
  60         if (obj->ops->shrink) {
  61                 unsigned int shrink_flags = 0;
  62
  63                 if (!(flags & I915_SHRINK_ACTIVE))
  64                         shrink_flags |= I915_GEM_OBJECT_SHRINK_NO_GPU_WAIT;
  65
  66                 if (flags & I915_SHRINK_WRITEBACK)
  67                         shrink_flags |= I915_GEM_OBJECT_SHRINK_WRITEBACK;
  68
  69                 return obj->ops->shrink(obj, shrink_flags);
  70         }
  71
  72         return 0;
  73 }
  74
  75 /**
  76  * i915_gem_shrink - Shrink buffer object caches
  77  * @ww: i915 gem ww acquire ctx, or NULL
  78  * @i915: i915 device
  79  * @target: amount of memory to make available, in pages
  80  * @nr_scanned: optional output for number of pages scanned (incremental)
  81  * @shrink: control flags for selecting cache types
  82  *
  83  * This function is the main interface to the shrinker. It will try to release
  84  * up to @target pages of main memory backing storage from buffer objects.
  85  * Selection of the specific caches can be done with @flags. This is e.g. useful
  86  * when purgeable objects should be removed from caches preferentially.
  87  *
  88  * Note that it's not guaranteed that released amount is actually available as
  89  * free system memory - the pages might still be in-used to due to other reasons
  90  * (like cpu mmaps) or the mm core has reused them before we could grab them.
  91  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
  92  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
  93  *
  94  * Also note that any kind of pinning (both per-vma address space pins and
  95  * backing storage pins at the buffer object level) result in the shrinker code
  96  * having to skip the object.
  97  *
  98  * Returns:
  99  * The number of pages of backing storage actually released.
 100  */
 101 unsigned long
 102 i915_gem_shrink(struct i915_gem_ww_ctx *ww,
 103                 struct drm_i915_private *i915,
 104                 unsigned long target,
 105                 unsigned long *nr_scanned,
 106                 unsigned int shrink)
 107 {
 108         const struct {
 109                 struct list_head *list;
 110                 unsigned int bit;
 111         } phases[] = {
 112                 { &i915->mm.purge_list, ~0u },
 113                 {
 114                         &i915->mm.shrink_list,
 115                         I915_SHRINK_BOUND | I915_SHRINK_UNBOUND
 116                 },
 117                 { NULL, 0 },
 118         }, *phase;
 119         intel_wakeref_t wakeref = 0;
 120         unsigned long count = 0;
 121         unsigned long scanned = 0;
 122         int err = 0;
 123
 124         /* CHV + VTD workaround use stop_machine(); need to trylock vm->mutex */
 125         bool trylock_vm = !ww && intel_vm_no_concurrent_access_wa(i915);
 126
 127         trace_i915_gem_shrink(i915, target, shrink);
 128
 129         /*
 130          * Unbinding of objects will require HW access; Let us not wake the
 131          * device just to recover a little memory. If absolutely necessary,
 132          * we will force the wake during oom-notifier.
 133          */
 134         if (shrink & I915_SHRINK_BOUND) {
 135                 wakeref = intel_runtime_pm_get_if_in_use(&i915->runtime_pm);
 136                 if (!wakeref)
 137                         shrink &= ~I915_SHRINK_BOUND;
 138         }
 139
 140         /*
 141          * When shrinking the active list, we should also consider active
 142          * contexts. Active contexts are pinned until they are retired, and
 143          * so can not be simply unbound to retire and unpin their pages. To
 144          * shrink the contexts, we must wait until the gpu is idle and
 145          * completed its switch to the kernel context. In short, we do
 146          * not have a good mechanism for idling a specific context, but
 147          * what we can do is give them a kick so that we do not keep idle
 148          * contexts around longer than is necessary.
 149          */
 150         if (shrink & I915_SHRINK_ACTIVE)
 151                 /* Retire requests to unpin all idle contexts */
 152                 intel_gt_retire_requests(to_gt(i915));
 153
 154         /*
 155          * As we may completely rewrite the (un)bound list whilst unbinding
 156          * (due to retiring requests) we have to strictly process only
 157          * one element of the list at the time, and recheck the list
 158          * on every iteration.
 159          *
 160          * In particular, we must hold a reference whilst removing the
 161          * object as we may end up waiting for and/or retiring the objects.
 162          * This might release the final reference (held by the active list)
 163          * and result in the object being freed from under us. This is
 164          * similar to the precautions the eviction code must take whilst
 165          * removing objects.
 166          *
 167          * Also note that although these lists do not hold a reference to
 168          * the object we can safely grab one here: The final object
 169          * unreferencing and the bound_list are both protected by the
 170          * dev->struct_mutex and so we won't ever be able to observe an
 171          * object on the bound_list with a reference count equals 0.
 172          */
 173         for (phase = phases; phase->list; phase++) {
 174                 struct list_head still_in_list;
 175                 struct drm_i915_gem_object *obj;
 176                 unsigned long flags;
 177
 178                 if ((shrink & phase->bit) == 0)
 179                         continue;
 180
 181                 INIT_LIST_HEAD(&still_in_list);
 182
 183                 /*
 184                  * We serialize our access to unreferenced objects through
 185                  * the use of the struct_mutex. While the objects are not
 186                  * yet freed (due to RCU then a workqueue) we still want
 187                  * to be able to shrink their pages, so they remain on
 188                  * the unbound/bound list until actually freed.
 189                  */
 190                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
 191                 while (count < target &&
 192                        (obj = list_first_entry_or_null(phase->list,
 193                                                        typeof(*obj),
 194                                                        mm.link))) {
 195                         list_move_tail(&obj->mm.link, &still_in_list);
 196
 197                         if (shrink & I915_SHRINK_VMAPS &&
 198                             !is_vmalloc_addr(obj->mm.mapping))
 199                                 continue;
 200
 201                         if (!(shrink & I915_SHRINK_ACTIVE) &&
 202                             i915_gem_object_is_framebuffer(obj))
 203                                 continue;
 204
 205                         if (!can_release_pages(obj))
 206                                 continue;
 207
 208                         if (!kref_get_unless_zero(&obj->base.refcount))
 209                                 continue;
 210
 211                         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 212
 213                         /* May arrive from get_pages on another bo */
 214                         if (!ww) {
 215                                 if (!i915_gem_object_trylock(obj, NULL))
 216                                         goto skip;
 217                         } else {
 218                                 err = i915_gem_object_lock(obj, ww);
 219                                 if (err)
 220                                         goto skip;
 221                         }
 222
 223                         if (drop_pages(obj, shrink, trylock_vm) &&
 224                             !__i915_gem_object_put_pages(obj) &&
 225                             !try_to_writeback(obj, shrink))
 226                                 count += obj->base.size >> PAGE_SHIFT;
 227
 228                         if (!ww)
 229                                 i915_gem_object_unlock(obj);
 230
 231                         scanned += obj->base.size >> PAGE_SHIFT;
 232 skip:
 233                         i915_gem_object_put(obj);
 234
 235                         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 236                         if (err)
 237                                 break;
 238                 }
 239                 list_splice_tail(&still_in_list, phase->list);
 240                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 241                 if (err)
 242                         break;
 243         }
 244
 245         if (shrink & I915_SHRINK_BOUND)
 246                 intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 247
 248         if (err)
 249                 return err;
 250
 251         if (nr_scanned)
 252                 *nr_scanned += scanned;
 253         return count;
 254 }
 255
 256 /**
 257  * i915_gem_shrink_all - Shrink buffer object caches completely
 258  * @i915: i915 device
 259  *
 260  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
 261  * caches completely. It also first waits for and retires all outstanding
 262  * requests to also be able to release backing storage for active objects.
 263  *
 264  * This should only be used in code to intentionally quiescent the gpu or as a
 265  * last-ditch effort when memory seems to have run out.
 266  *
 267  * Returns:
 268  * The number of pages of backing storage actually released.
 269  */
 270 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915)
 271 {
 272         intel_wakeref_t wakeref;
 273         unsigned long freed = 0;
 274
 275         with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 276                 freed = i915_gem_shrink(NULL, i915, -1UL, NULL,
 277                                         I915_SHRINK_BOUND |
 278                                         I915_SHRINK_UNBOUND);
 279         }
 280
 281         return freed;
 282 }
 283
 284 static unsigned long
 285 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 286 {
 287         struct drm_i915_private *i915 =
 288                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 289         unsigned long num_objects;
 290         unsigned long count;
 291
 292         count = READ_ONCE(i915->mm.shrink_memory) >> PAGE_SHIFT;
 293         num_objects = READ_ONCE(i915->mm.shrink_count);
 294
 295         /*
 296          * Update our preferred vmscan batch size for the next pass.
 297          * Our rough guess for an effective batch size is roughly 2
 298          * available GEM objects worth of pages. That is we don't want
 299          * the shrinker to fire, until it is worth the cost of freeing an
 300          * entire GEM object.
 301          */
 302         if (num_objects) {
 303                 unsigned long avg = 2 * count / num_objects;
 304
 305                 i915->mm.shrinker.batch =
 306                         max((i915->mm.shrinker.batch + avg) >> 1,
 307                             128ul /* default SHRINK_BATCH */);
 308         }
 309
 310         return count;
 311 }
 312
 313 static unsigned long
 314 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 315 {
 316         struct drm_i915_private *i915 =
 317                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 318         unsigned long freed;
 319
 320         sc->nr_scanned = 0;
 321
 322         freed = i915_gem_shrink(NULL, i915,
 323                                 sc->nr_to_scan,
 324                                 &sc->nr_scanned,
 325                                 I915_SHRINK_BOUND |
 326                                 I915_SHRINK_UNBOUND);
 327         if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
 328                 intel_wakeref_t wakeref;
 329
 330                 with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 331                         freed += i915_gem_shrink(NULL, i915,
 332                                                  sc->nr_to_scan - sc->nr_scanned,
 333                                                  &sc->nr_scanned,
 334                                                  I915_SHRINK_ACTIVE |
 335                                                  I915_SHRINK_BOUND |
 336                                                  I915_SHRINK_UNBOUND |
 337                                                  I915_SHRINK_WRITEBACK);
 338                 }
 339         }
 340
 341         return sc->nr_scanned ? freed : SHRINK_STOP;
 342 }
 343
 344 static int
 345 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 346 {
 347         struct drm_i915_private *i915 =
 348                 container_of(nb, struct drm_i915_private, mm.oom_notifier);
 349         struct drm_i915_gem_object *obj;
 350         unsigned long unevictable, available, freed_pages;
 351         intel_wakeref_t wakeref;
 352         unsigned long flags;
 353
 354         freed_pages = 0;
 355         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 356                 freed_pages += i915_gem_shrink(NULL, i915, -1UL, NULL,
 357                                                I915_SHRINK_BOUND |
 358                                                I915_SHRINK_UNBOUND |
 359                                                I915_SHRINK_WRITEBACK);
 360
 361         /* Because we may be allocating inside our own driver, we cannot
 362          * assert that there are no objects with pinned pages that are not
 363          * being pointed to by hardware.
 364          */
 365         available = unevictable = 0;
 366         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 367         list_for_each_entry(obj, &i915->mm.shrink_list, mm.link) {
 368                 if (!can_release_pages(obj))
 369                         unevictable += obj->base.size >> PAGE_SHIFT;
 370                 else
 371                         available += obj->base.size >> PAGE_SHIFT;
 372         }
 373         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 374
 375         if (freed_pages || available)
 376                 pr_info("Purging GPU memory, %lu pages freed, "
 377                         "%lu pages still pinned, %lu pages left available.\n",
 378                         freed_pages, unevictable, available);
 379
 380         *(unsigned long *)ptr += freed_pages;
 381         return NOTIFY_DONE;
 382 }
 383
 384 static int
 385 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 386 {
 387         struct drm_i915_private *i915 =
 388                 container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 389         struct i915_vma *vma, *next;
 390         unsigned long freed_pages = 0;
 391         intel_wakeref_t wakeref;
 392
 393         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 394                 freed_pages += i915_gem_shrink(NULL, i915, -1UL, NULL,
 395                                                I915_SHRINK_BOUND |
 396                                                I915_SHRINK_UNBOUND |
 397                                                I915_SHRINK_VMAPS);
 398
 399         /* We also want to clear any cached iomaps as they wrap vmap */
 400         mutex_lock(&to_gt(i915)->ggtt->vm.mutex);
 401         list_for_each_entry_safe(vma, next,
 402                                  &to_gt(i915)->ggtt->vm.bound_list, vm_link) {
 403                 unsigned long count = i915_vma_size(vma) >> PAGE_SHIFT;
 404                 struct drm_i915_gem_object *obj = vma->obj;
 405
 406                 if (!vma->iomap || i915_vma_is_active(vma))
 407                         continue;
 408
 409                 if (!i915_gem_object_trylock(obj, NULL))
 410                         continue;
 411
 412                 if (__i915_vma_unbind(vma) == 0)
 413                         freed_pages += count;
 414
 415                 i915_gem_object_unlock(obj);
 416         }
 417         mutex_unlock(&to_gt(i915)->ggtt->vm.mutex);
 418
 419         *(unsigned long *)ptr += freed_pages;
 420         return NOTIFY_DONE;
 421 }
 422
 423 void i915_gem_driver_register__shrinker(struct drm_i915_private *i915)
 424 {
 425         i915->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 426         i915->mm.shrinker.count_objects = i915_gem_shrinker_count;
 427         i915->mm.shrinker.seeks = DEFAULT_SEEKS;
 428         i915->mm.shrinker.batch = 4096;
 429         drm_WARN_ON(&i915->drm, register_shrinker(&i915->mm.shrinker,
 430                                                   "drm-i915_gem"));
 431
 432         i915->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 433         drm_WARN_ON(&i915->drm, register_oom_notifier(&i915->mm.oom_notifier));
 434
 435         i915->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
 436         drm_WARN_ON(&i915->drm,
 437                     register_vmap_purge_notifier(&i915->mm.vmap_notifier));
 438 }
 439
 440 void i915_gem_driver_unregister__shrinker(struct drm_i915_private *i915)
 441 {
 442         drm_WARN_ON(&i915->drm,
 443                     unregister_vmap_purge_notifier(&i915->mm.vmap_notifier));
 444         drm_WARN_ON(&i915->drm,
 445                     unregister_oom_notifier(&i915->mm.oom_notifier));
 446         unregister_shrinker(&i915->mm.shrinker);
 447 }
 448
 449 void i915_gem_shrinker_taints_mutex(struct drm_i915_private *i915,
 450                                     struct mutex *mutex)
 451 {
 452         if (!IS_ENABLED(CONFIG_LOCKDEP))
 453                 return;
 454
 455         fs_reclaim_acquire(GFP_KERNEL);
 456
 457         mutex_acquire(&mutex->dep_map, 0, 0, _RET_IP_);
 458         mutex_release(&mutex->dep_map, _RET_IP_);
 459
 460         fs_reclaim_release(GFP_KERNEL);
 461 }
 462
 463 /**
 464  * i915_gem_object_make_unshrinkable - Hide the object from the shrinker. By
 465  * default all object types that support shrinking(see IS_SHRINKABLE), will also
 466  * make the object visible to the shrinker after allocating the system memory
 467  * pages.
 468  * @obj: The GEM object.
 469  *
 470  * This is typically used for special kernel internal objects that can't be
 471  * easily processed by the shrinker, like if they are perma-pinned.
 472  */
 473 void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj)
 474 {
 475         struct drm_i915_private *i915 = obj_to_i915(obj);
 476         unsigned long flags;
 477
 478         /*
 479          * We can only be called while the pages are pinned or when
 480          * the pages are released. If pinned, we should only be called
 481          * from a single caller under controlled conditions; and on release
 482          * only one caller may release us. Neither the two may cross.
 483          */
 484         if (atomic_add_unless(&obj->mm.shrink_pin, 1, 0))
 485                 return;
 486
 487         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 488         if (!atomic_fetch_inc(&obj->mm.shrink_pin) &&
 489             !list_empty(&obj->mm.link)) {
 490                 list_del_init(&obj->mm.link);
 491                 i915->mm.shrink_count--;
 492                 i915->mm.shrink_memory -= obj->base.size;
 493         }
 494         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 495 }
 496
 497 static void ___i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj,
 498                                                struct list_head *head)
 499 {
 500         struct drm_i915_private *i915 = obj_to_i915(obj);
 501         unsigned long flags;
 502
 503         if (!i915_gem_object_is_shrinkable(obj))
 504                 return;
 505
 506         if (atomic_add_unless(&obj->mm.shrink_pin, -1, 1))
 507                 return;
 508
 509         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 510         GEM_BUG_ON(!kref_read(&obj->base.refcount));
 511         if (atomic_dec_and_test(&obj->mm.shrink_pin)) {
 512                 GEM_BUG_ON(!list_empty(&obj->mm.link));
 513
 514                 list_add_tail(&obj->mm.link, head);
 515                 i915->mm.shrink_count++;
 516                 i915->mm.shrink_memory += obj->base.size;
 517
 518         }
 519         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 520 }
 521
 522 /**
 523  * __i915_gem_object_make_shrinkable - Move the object to the tail of the
 524  * shrinkable list. Objects on this list might be swapped out. Used with
 525  * WILLNEED objects.
 526  * @obj: The GEM object.
 527  *
 528  * DO NOT USE. This is intended to be called on very special objects that don't
 529  * yet have mm.pages, but are guaranteed to have potentially reclaimable pages
 530  * underneath.
 531  */
 532 void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 533 {
 534         ___i915_gem_object_make_shrinkable(obj,
 535                                            &obj_to_i915(obj)->mm.shrink_list);
 536 }
 537
 538 /**
 539  * __i915_gem_object_make_purgeable - Move the object to the tail of the
 540  * purgeable list. Objects on this list might be swapped out. Used with
 541  * DONTNEED objects.
 542  * @obj: The GEM object.
 543  *
 544  * DO NOT USE. This is intended to be called on very special objects that don't
 545  * yet have mm.pages, but are guaranteed to have potentially reclaimable pages
 546  * underneath.
 547  */
 548 void __i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 549 {
 550         ___i915_gem_object_make_shrinkable(obj,
 551                                            &obj_to_i915(obj)->mm.purge_list);
 552 }
 553
 554 /**
 555  * i915_gem_object_make_shrinkable - Move the object to the tail of the
 556  * shrinkable list. Objects on this list might be swapped out. Used with
 557  * WILLNEED objects.
 558  * @obj: The GEM object.
 559  *
 560  * MUST only be called on objects which have backing pages.
 561  *
 562  * MUST be balanced with previous call to i915_gem_object_make_unshrinkable().
 563  */
 564 void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 565 {
 566         GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 567         __i915_gem_object_make_shrinkable(obj);
 568 }
 569
 570 /**
 571  * i915_gem_object_make_purgeable - Move the object to the tail of the purgeable
 572  * list. Used with DONTNEED objects. Unlike with shrinkable objects, the
 573  * shrinker will attempt to discard the backing pages, instead of trying to swap
 574  * them out.
 575  * @obj: The GEM object.
 576  *
 577  * MUST only be called on objects which have backing pages.
 578  *
 579  * MUST be balanced with previous call to i915_gem_object_make_unshrinkable().
 580  */
 581 void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 582 {
 583         GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 584         __i915_gem_object_make_purgeable(obj);
 585 }