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 unsafe_drop_pages(struct drm_i915_gem_object *obj,
  40                               unsigned long shrink)
  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
  50         if (i915_gem_object_unbind(obj, flags) == 0)
  51                 __i915_gem_object_put_pages(obj);
  52
  53         return !i915_gem_object_has_pages(obj);
  54 }
  55
  56 static void try_to_writeback(struct drm_i915_gem_object *obj,
  57                              unsigned int flags)
  58 {
  59         switch (obj->mm.madv) {
  60         case I915_MADV_DONTNEED:
  61                 i915_gem_object_truncate(obj);
  62         case __I915_MADV_PURGED:
  63                 return;
  64         }
  65
  66         if (flags & I915_SHRINK_WRITEBACK)
  67                 i915_gem_object_writeback(obj);
  68 }
  69
  70 /**
  71  * i915_gem_shrink - Shrink buffer object caches
  72  * @i915: i915 device
  73  * @target: amount of memory to make available, in pages
  74  * @nr_scanned: optional output for number of pages scanned (incremental)
  75  * @shrink: control flags for selecting cache types
  76  *
  77  * This function is the main interface to the shrinker. It will try to release
  78  * up to @target pages of main memory backing storage from buffer objects.
  79  * Selection of the specific caches can be done with @flags. This is e.g. useful
  80  * when purgeable objects should be removed from caches preferentially.
  81  *
  82  * Note that it's not guaranteed that released amount is actually available as
  83  * free system memory - the pages might still be in-used to due to other reasons
  84  * (like cpu mmaps) or the mm core has reused them before we could grab them.
  85  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
  86  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
  87  *
  88  * Also note that any kind of pinning (both per-vma address space pins and
  89  * backing storage pins at the buffer object level) result in the shrinker code
  90  * having to skip the object.
  91  *
  92  * Returns:
  93  * The number of pages of backing storage actually released.
  94  */
  95 unsigned long
  96 i915_gem_shrink(struct drm_i915_private *i915,
  97                 unsigned long target,
  98                 unsigned long *nr_scanned,
  99                 unsigned int shrink)
 100 {
 101         const struct {
 102                 struct list_head *list;
 103                 unsigned int bit;
 104         } phases[] = {
 105                 { &i915->mm.purge_list, ~0u },
 106                 {
 107                         &i915->mm.shrink_list,
 108                         I915_SHRINK_BOUND | I915_SHRINK_UNBOUND
 109                 },
 110                 { NULL, 0 },
 111         }, *phase;
 112         intel_wakeref_t wakeref = 0;
 113         unsigned long count = 0;
 114         unsigned long scanned = 0;
 115
 116         trace_i915_gem_shrink(i915, target, shrink);
 117
 118         /*
 119          * Unbinding of objects will require HW access; Let us not wake the
 120          * device just to recover a little memory. If absolutely necessary,
 121          * we will force the wake during oom-notifier.
 122          */
 123         if (shrink & I915_SHRINK_BOUND) {
 124                 wakeref = intel_runtime_pm_get_if_in_use(&i915->runtime_pm);
 125                 if (!wakeref)
 126                         shrink &= ~I915_SHRINK_BOUND;
 127         }
 128
 129         /*
 130          * When shrinking the active list, we should also consider active
 131          * contexts. Active contexts are pinned until they are retired, and
 132          * so can not be simply unbound to retire and unpin their pages. To
 133          * shrink the contexts, we must wait until the gpu is idle and
 134          * completed its switch to the kernel context. In short, we do
 135          * not have a good mechanism for idling a specific context, but
 136          * what we can do is give them a kick so that we do not keep idle
 137          * contexts around longer than is necessary.
 138          */
 139         if (shrink & I915_SHRINK_ACTIVE)
 140                 /* Retire requests to unpin all idle contexts */
 141                 intel_gt_retire_requests(&i915->gt);
 142
 143         /*
 144          * As we may completely rewrite the (un)bound list whilst unbinding
 145          * (due to retiring requests) we have to strictly process only
 146          * one element of the list at the time, and recheck the list
 147          * on every iteration.
 148          *
 149          * In particular, we must hold a reference whilst removing the
 150          * object as we may end up waiting for and/or retiring the objects.
 151          * This might release the final reference (held by the active list)
 152          * and result in the object being freed from under us. This is
 153          * similar to the precautions the eviction code must take whilst
 154          * removing objects.
 155          *
 156          * Also note that although these lists do not hold a reference to
 157          * the object we can safely grab one here: The final object
 158          * unreferencing and the bound_list are both protected by the
 159          * dev->struct_mutex and so we won't ever be able to observe an
 160          * object on the bound_list with a reference count equals 0.
 161          */
 162         for (phase = phases; phase->list; phase++) {
 163                 struct list_head still_in_list;
 164                 struct drm_i915_gem_object *obj;
 165                 unsigned long flags;
 166
 167                 if ((shrink & phase->bit) == 0)
 168                         continue;
 169
 170                 INIT_LIST_HEAD(&still_in_list);
 171
 172                 /*
 173                  * We serialize our access to unreferenced objects through
 174                  * the use of the struct_mutex. While the objects are not
 175                  * yet freed (due to RCU then a workqueue) we still want
 176                  * to be able to shrink their pages, so they remain on
 177                  * the unbound/bound list until actually freed.
 178                  */
 179                 spin_lock_irqsave(&i915->mm.obj_lock, flags);
 180                 while (count < target &&
 181                        (obj = list_first_entry_or_null(phase->list,
 182                                                        typeof(*obj),
 183                                                        mm.link))) {
 184                         list_move_tail(&obj->mm.link, &still_in_list);
 185
 186                         if (shrink & I915_SHRINK_VMAPS &&
 187                             !is_vmalloc_addr(obj->mm.mapping))
 188                                 continue;
 189
 190                         if (!(shrink & I915_SHRINK_ACTIVE) &&
 191                             i915_gem_object_is_framebuffer(obj))
 192                                 continue;
 193
 194                         if (!can_release_pages(obj))
 195                                 continue;
 196
 197                         if (!kref_get_unless_zero(&obj->base.refcount))
 198                                 continue;
 199
 200                         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 201
 202                         if (unsafe_drop_pages(obj, shrink)) {
 203                                 /* May arrive from get_pages on another bo */
 204                                 mutex_lock(&obj->mm.lock);
 205                                 if (!i915_gem_object_has_pages(obj)) {
 206                                         try_to_writeback(obj, shrink);
 207                                         count += obj->base.size >> PAGE_SHIFT;
 208                                 }
 209                                 mutex_unlock(&obj->mm.lock);
 210                         }
 211
 212                         scanned += obj->base.size >> PAGE_SHIFT;
 213                         i915_gem_object_put(obj);
 214
 215                         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 216                 }
 217                 list_splice_tail(&still_in_list, phase->list);
 218                 spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 219         }
 220
 221         if (shrink & I915_SHRINK_BOUND)
 222                 intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 223
 224         if (nr_scanned)
 225                 *nr_scanned += scanned;
 226         return count;
 227 }
 228
 229 /**
 230  * i915_gem_shrink_all - Shrink buffer object caches completely
 231  * @i915: i915 device
 232  *
 233  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
 234  * caches completely. It also first waits for and retires all outstanding
 235  * requests to also be able to release backing storage for active objects.
 236  *
 237  * This should only be used in code to intentionally quiescent the gpu or as a
 238  * last-ditch effort when memory seems to have run out.
 239  *
 240  * Returns:
 241  * The number of pages of backing storage actually released.
 242  */
 243 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915)
 244 {
 245         intel_wakeref_t wakeref;
 246         unsigned long freed = 0;
 247
 248         with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 249                 freed = i915_gem_shrink(i915, -1UL, NULL,
 250                                         I915_SHRINK_BOUND |
 251                                         I915_SHRINK_UNBOUND);
 252         }
 253
 254         return freed;
 255 }
 256
 257 static unsigned long
 258 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 259 {
 260         struct drm_i915_private *i915 =
 261                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 262         unsigned long num_objects;
 263         unsigned long count;
 264
 265         count = READ_ONCE(i915->mm.shrink_memory) >> PAGE_SHIFT;
 266         num_objects = READ_ONCE(i915->mm.shrink_count);
 267
 268         /*
 269          * Update our preferred vmscan batch size for the next pass.
 270          * Our rough guess for an effective batch size is roughly 2
 271          * available GEM objects worth of pages. That is we don't want
 272          * the shrinker to fire, until it is worth the cost of freeing an
 273          * entire GEM object.
 274          */
 275         if (num_objects) {
 276                 unsigned long avg = 2 * count / num_objects;
 277
 278                 i915->mm.shrinker.batch =
 279                         max((i915->mm.shrinker.batch + avg) >> 1,
 280                             128ul /* default SHRINK_BATCH */);
 281         }
 282
 283         return count;
 284 }
 285
 286 static unsigned long
 287 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 288 {
 289         struct drm_i915_private *i915 =
 290                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 291         unsigned long freed;
 292
 293         sc->nr_scanned = 0;
 294
 295         freed = i915_gem_shrink(i915,
 296                                 sc->nr_to_scan,
 297                                 &sc->nr_scanned,
 298                                 I915_SHRINK_BOUND |
 299                                 I915_SHRINK_UNBOUND);
 300         if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
 301                 intel_wakeref_t wakeref;
 302
 303                 with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 304                         freed += i915_gem_shrink(i915,
 305                                                  sc->nr_to_scan - sc->nr_scanned,
 306                                                  &sc->nr_scanned,
 307                                                  I915_SHRINK_ACTIVE |
 308                                                  I915_SHRINK_BOUND |
 309                                                  I915_SHRINK_UNBOUND |
 310                                                  I915_SHRINK_WRITEBACK);
 311                 }
 312         }
 313
 314         return sc->nr_scanned ? freed : SHRINK_STOP;
 315 }
 316
 317 static int
 318 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 319 {
 320         struct drm_i915_private *i915 =
 321                 container_of(nb, struct drm_i915_private, mm.oom_notifier);
 322         struct drm_i915_gem_object *obj;
 323         unsigned long unevictable, available, freed_pages;
 324         intel_wakeref_t wakeref;
 325         unsigned long flags;
 326
 327         freed_pages = 0;
 328         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 329                 freed_pages += i915_gem_shrink(i915, -1UL, NULL,
 330                                                I915_SHRINK_BOUND |
 331                                                I915_SHRINK_UNBOUND |
 332                                                I915_SHRINK_WRITEBACK);
 333
 334         /* Because we may be allocating inside our own driver, we cannot
 335          * assert that there are no objects with pinned pages that are not
 336          * being pointed to by hardware.
 337          */
 338         available = unevictable = 0;
 339         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 340         list_for_each_entry(obj, &i915->mm.shrink_list, mm.link) {
 341                 if (!can_release_pages(obj))
 342                         unevictable += obj->base.size >> PAGE_SHIFT;
 343                 else
 344                         available += obj->base.size >> PAGE_SHIFT;
 345         }
 346         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 347
 348         if (freed_pages || available)
 349                 pr_info("Purging GPU memory, %lu pages freed, "
 350                         "%lu pages still pinned, %lu pages left available.\n",
 351                         freed_pages, unevictable, available);
 352
 353         *(unsigned long *)ptr += freed_pages;
 354         return NOTIFY_DONE;
 355 }
 356
 357 static int
 358 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 359 {
 360         struct drm_i915_private *i915 =
 361                 container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 362         struct i915_vma *vma, *next;
 363         unsigned long freed_pages = 0;
 364         intel_wakeref_t wakeref;
 365
 366         with_intel_runtime_pm(&i915->runtime_pm, wakeref)
 367                 freed_pages += i915_gem_shrink(i915, -1UL, NULL,
 368                                                I915_SHRINK_BOUND |
 369                                                I915_SHRINK_UNBOUND |
 370                                                I915_SHRINK_VMAPS);
 371
 372         /* We also want to clear any cached iomaps as they wrap vmap */
 373         mutex_lock(&i915->ggtt.vm.mutex);
 374         list_for_each_entry_safe(vma, next,
 375                                  &i915->ggtt.vm.bound_list, vm_link) {
 376                 unsigned long count = vma->node.size >> PAGE_SHIFT;
 377
 378                 if (!vma->iomap || i915_vma_is_active(vma))
 379                         continue;
 380
 381                 if (__i915_vma_unbind(vma) == 0)
 382                         freed_pages += count;
 383         }
 384         mutex_unlock(&i915->ggtt.vm.mutex);
 385
 386         *(unsigned long *)ptr += freed_pages;
 387         return NOTIFY_DONE;
 388 }
 389
 390 void i915_gem_driver_register__shrinker(struct drm_i915_private *i915)
 391 {
 392         i915->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 393         i915->mm.shrinker.count_objects = i915_gem_shrinker_count;
 394         i915->mm.shrinker.seeks = DEFAULT_SEEKS;
 395         i915->mm.shrinker.batch = 4096;
 396         drm_WARN_ON(&i915->drm, register_shrinker(&i915->mm.shrinker));
 397
 398         i915->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 399         drm_WARN_ON(&i915->drm, register_oom_notifier(&i915->mm.oom_notifier));
 400
 401         i915->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
 402         drm_WARN_ON(&i915->drm,
 403                     register_vmap_purge_notifier(&i915->mm.vmap_notifier));
 404 }
 405
 406 void i915_gem_driver_unregister__shrinker(struct drm_i915_private *i915)
 407 {
 408         drm_WARN_ON(&i915->drm,
 409                     unregister_vmap_purge_notifier(&i915->mm.vmap_notifier));
 410         drm_WARN_ON(&i915->drm,
 411                     unregister_oom_notifier(&i915->mm.oom_notifier));
 412         unregister_shrinker(&i915->mm.shrinker);
 413 }
 414
 415 void i915_gem_shrinker_taints_mutex(struct drm_i915_private *i915,
 416                                     struct mutex *mutex)
 417 {
 418         if (!IS_ENABLED(CONFIG_LOCKDEP))
 419                 return;
 420
 421         fs_reclaim_acquire(GFP_KERNEL);
 422
 423         mutex_acquire(&mutex->dep_map, 0, 0, _RET_IP_);
 424         mutex_release(&mutex->dep_map, _RET_IP_);
 425
 426         fs_reclaim_release(GFP_KERNEL);
 427 }
 428
 429 #define obj_to_i915(obj__) to_i915((obj__)->base.dev)
 430
 431 void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj)
 432 {
 433         struct drm_i915_private *i915 = obj_to_i915(obj);
 434         unsigned long flags;
 435
 436         /*
 437          * We can only be called while the pages are pinned or when
 438          * the pages are released. If pinned, we should only be called
 439          * from a single caller under controlled conditions; and on release
 440          * only one caller may release us. Neither the two may cross.
 441          */
 442         if (atomic_add_unless(&obj->mm.shrink_pin, 1, 0))
 443                 return;
 444
 445         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 446         if (!atomic_fetch_inc(&obj->mm.shrink_pin) &&
 447             !list_empty(&obj->mm.link)) {
 448                 list_del_init(&obj->mm.link);
 449                 i915->mm.shrink_count--;
 450                 i915->mm.shrink_memory -= obj->base.size;
 451         }
 452         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 453 }
 454
 455 static void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj,
 456                                               struct list_head *head)
 457 {
 458         struct drm_i915_private *i915 = obj_to_i915(obj);
 459         unsigned long flags;
 460
 461         GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 462         if (!i915_gem_object_is_shrinkable(obj))
 463                 return;
 464
 465         if (atomic_add_unless(&obj->mm.shrink_pin, -1, 1))
 466                 return;
 467
 468         spin_lock_irqsave(&i915->mm.obj_lock, flags);
 469         GEM_BUG_ON(!kref_read(&obj->base.refcount));
 470         if (atomic_dec_and_test(&obj->mm.shrink_pin)) {
 471                 GEM_BUG_ON(!list_empty(&obj->mm.link));
 472
 473                 list_add_tail(&obj->mm.link, head);
 474                 i915->mm.shrink_count++;
 475                 i915->mm.shrink_memory += obj->base.size;
 476
 477         }
 478         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 479 }
 480
 481 void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 482 {
 483         __i915_gem_object_make_shrinkable(obj,
 484                                           &obj_to_i915(obj)->mm.shrink_list);
 485 }
 486
 487 void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 488 {
 489         __i915_gem_object_make_shrinkable(obj,
 490                                           &obj_to_i915(obj)->mm.purge_list);
 491 }