drivers/gpu/drm/i915/i915_gem_shrinker.c

   1 /*
   2  * Copyright © 2008-2015 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  */
  24
  25 #include <linux/oom.h>
  26 #include <linux/shmem_fs.h>
  27 #include <linux/slab.h>
  28 #include <linux/swap.h>
  29 #include <linux/pci.h>
  30 #include <linux/dma-buf.h>
  31 #include <linux/vmalloc.h>
  32 #include <drm/drmP.h>
  33 #include <drm/i915_drm.h>
  34
  35 #include "i915_drv.h"
  36 #include "i915_trace.h"
  37
  38 static bool shrinker_lock(struct drm_i915_private *dev_priv, bool *unlock)
  39 {
  40         switch (mutex_trylock_recursive(&dev_priv->drm.struct_mutex)) {
  41         case MUTEX_TRYLOCK_RECURSIVE:
  42                 *unlock = false;
  43                 return true;
  44
  45         case MUTEX_TRYLOCK_FAILED:
  46                 *unlock = false;
  47                 preempt_disable();
  48                 do {
  49                         cpu_relax();
  50                         if (mutex_trylock(&dev_priv->drm.struct_mutex)) {
  51                                 *unlock = true;
  52                                 break;
  53                         }
  54                 } while (!need_resched());
  55                 preempt_enable();
  56                 return *unlock;
  57
  58         case MUTEX_TRYLOCK_SUCCESS:
  59                 *unlock = true;
  60                 return true;
  61         }
  62
  63         BUG();
  64 }
  65
  66 static void shrinker_unlock(struct drm_i915_private *dev_priv, bool unlock)
  67 {
  68         if (!unlock)
  69                 return;
  70
  71         mutex_unlock(&dev_priv->drm.struct_mutex);
  72 }
  73
  74 static bool swap_available(void)
  75 {
  76         return get_nr_swap_pages() > 0;
  77 }
  78
  79 static bool can_release_pages(struct drm_i915_gem_object *obj)
  80 {
  81         /* Consider only shrinkable ojects. */
  82         if (!i915_gem_object_is_shrinkable(obj))
  83                 return false;
  84
  85         /* Only report true if by unbinding the object and putting its pages
  86          * we can actually make forward progress towards freeing physical
  87          * pages.
  88          *
  89          * If the pages are pinned for any other reason than being bound
  90          * to the GPU, simply unbinding from the GPU is not going to succeed
  91          * in releasing our pin count on the pages themselves.
  92          */
  93         if (atomic_read(&obj->mm.pages_pin_count) > obj->bind_count)
  94                 return false;
  95
  96         /* If any vma are "permanently" pinned, it will prevent us from
  97          * reclaiming the obj->mm.pages. We only allow scanout objects to claim
  98          * a permanent pin, along with a few others like the context objects.
  99          * To simplify the scan, and to avoid walking the list of vma under the
 100          * object, we just check the count of its permanently pinned.
 101          */
 102         if (READ_ONCE(obj->pin_global))
 103                 return false;
 104
 105         /* We can only return physical pages to the system if we can either
 106          * discard the contents (because the user has marked them as being
 107          * purgeable) or if we can move their contents out to swap.
 108          */
 109         return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
 110 }
 111
 112 static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
 113 {
 114         if (i915_gem_object_unbind(obj) == 0)
 115                 __i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
 116         return !i915_gem_object_has_pages(obj);
 117 }
 118
 119 /**
 120  * i915_gem_shrink - Shrink buffer object caches
 121  * @dev_priv: i915 device
 122  * @target: amount of memory to make available, in pages
 123  * @nr_scanned: optional output for number of pages scanned (incremental)
 124  * @flags: control flags for selecting cache types
 125  *
 126  * This function is the main interface to the shrinker. It will try to release
 127  * up to @target pages of main memory backing storage from buffer objects.
 128  * Selection of the specific caches can be done with @flags. This is e.g. useful
 129  * when purgeable objects should be removed from caches preferentially.
 130  *
 131  * Note that it's not guaranteed that released amount is actually available as
 132  * free system memory - the pages might still be in-used to due to other reasons
 133  * (like cpu mmaps) or the mm core has reused them before we could grab them.
 134  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
 135  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
 136  *
 137  * Also note that any kind of pinning (both per-vma address space pins and
 138  * backing storage pins at the buffer object level) result in the shrinker code
 139  * having to skip the object.
 140  *
 141  * Returns:
 142  * The number of pages of backing storage actually released.
 143  */
 144 unsigned long
 145 i915_gem_shrink(struct drm_i915_private *dev_priv,
 146                 unsigned long target,
 147                 unsigned long *nr_scanned,
 148                 unsigned flags)
 149 {
 150         const struct {
 151                 struct list_head *list;
 152                 unsigned int bit;
 153         } phases[] = {
 154                 { &dev_priv->mm.unbound_list, I915_SHRINK_UNBOUND },
 155                 { &dev_priv->mm.bound_list, I915_SHRINK_BOUND },
 156                 { NULL, 0 },
 157         }, *phase;
 158         unsigned long count = 0;
 159         unsigned long scanned = 0;
 160         bool unlock;
 161
 162         if (!shrinker_lock(dev_priv, &unlock))
 163                 return 0;
 164
 165         /*
 166          * When shrinking the active list, also consider active contexts.
 167          * Active contexts are pinned until they are retired, and so can
 168          * not be simply unbound to retire and unpin their pages. To shrink
 169          * the contexts, we must wait until the gpu is idle.
 170          *
 171          * We don't care about errors here; if we cannot wait upon the GPU,
 172          * we will free as much as we can and hope to get a second chance.
 173          */
 174         if (flags & I915_SHRINK_ACTIVE)
 175                 i915_gem_wait_for_idle(dev_priv, I915_WAIT_LOCKED);
 176
 177         trace_i915_gem_shrink(dev_priv, target, flags);
 178         i915_gem_retire_requests(dev_priv);
 179
 180         /*
 181          * Unbinding of objects will require HW access; Let us not wake the
 182          * device just to recover a little memory. If absolutely necessary,
 183          * we will force the wake during oom-notifier.
 184          */
 185         if ((flags & I915_SHRINK_BOUND) &&
 186             !intel_runtime_pm_get_if_in_use(dev_priv))
 187                 flags &= ~I915_SHRINK_BOUND;
 188
 189         /*
 190          * As we may completely rewrite the (un)bound list whilst unbinding
 191          * (due to retiring requests) we have to strictly process only
 192          * one element of the list at the time, and recheck the list
 193          * on every iteration.
 194          *
 195          * In particular, we must hold a reference whilst removing the
 196          * object as we may end up waiting for and/or retiring the objects.
 197          * This might release the final reference (held by the active list)
 198          * and result in the object being freed from under us. This is
 199          * similar to the precautions the eviction code must take whilst
 200          * removing objects.
 201          *
 202          * Also note that although these lists do not hold a reference to
 203          * the object we can safely grab one here: The final object
 204          * unreferencing and the bound_list are both protected by the
 205          * dev->struct_mutex and so we won't ever be able to observe an
 206          * object on the bound_list with a reference count equals 0.
 207          */
 208         for (phase = phases; phase->list; phase++) {
 209                 struct list_head still_in_list;
 210                 struct drm_i915_gem_object *obj;
 211
 212                 if ((flags & phase->bit) == 0)
 213                         continue;
 214
 215                 INIT_LIST_HEAD(&still_in_list);
 216
 217                 /*
 218                  * We serialize our access to unreferenced objects through
 219                  * the use of the struct_mutex. While the objects are not
 220                  * yet freed (due to RCU then a workqueue) we still want
 221                  * to be able to shrink their pages, so they remain on
 222                  * the unbound/bound list until actually freed.
 223                  */
 224                 spin_lock(&dev_priv->mm.obj_lock);
 225                 while (count < target &&
 226                        (obj = list_first_entry_or_null(phase->list,
 227                                                        typeof(*obj),
 228                                                        mm.link))) {
 229                         list_move_tail(&obj->mm.link, &still_in_list);
 230
 231                         if (flags & I915_SHRINK_PURGEABLE &&
 232                             obj->mm.madv != I915_MADV_DONTNEED)
 233                                 continue;
 234
 235                         if (flags & I915_SHRINK_VMAPS &&
 236                             !is_vmalloc_addr(obj->mm.mapping))
 237                                 continue;
 238
 239                         if (!(flags & I915_SHRINK_ACTIVE) &&
 240                             (i915_gem_object_is_active(obj) ||
 241                              i915_gem_object_is_framebuffer(obj)))
 242                                 continue;
 243
 244                         if (!can_release_pages(obj))
 245                                 continue;
 246
 247                         spin_unlock(&dev_priv->mm.obj_lock);
 248
 249                         if (unsafe_drop_pages(obj)) {
 250                                 /* May arrive from get_pages on another bo */
 251                                 mutex_lock_nested(&obj->mm.lock,
 252                                                   I915_MM_SHRINKER);
 253                                 if (!i915_gem_object_has_pages(obj)) {
 254                                         __i915_gem_object_invalidate(obj);
 255                                         count += obj->base.size >> PAGE_SHIFT;
 256                                 }
 257                                 mutex_unlock(&obj->mm.lock);
 258                         }
 259                         scanned += obj->base.size >> PAGE_SHIFT;
 260
 261                         spin_lock(&dev_priv->mm.obj_lock);
 262                 }
 263                 list_splice_tail(&still_in_list, phase->list);
 264                 spin_unlock(&dev_priv->mm.obj_lock);
 265         }
 266
 267         if (flags & I915_SHRINK_BOUND)
 268                 intel_runtime_pm_put(dev_priv);
 269
 270         i915_gem_retire_requests(dev_priv);
 271
 272         shrinker_unlock(dev_priv, unlock);
 273
 274         if (nr_scanned)
 275                 *nr_scanned += scanned;
 276         return count;
 277 }
 278
 279 /**
 280  * i915_gem_shrink_all - Shrink buffer object caches completely
 281  * @dev_priv: i915 device
 282  *
 283  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
 284  * caches completely. It also first waits for and retires all outstanding
 285  * requests to also be able to release backing storage for active objects.
 286  *
 287  * This should only be used in code to intentionally quiescent the gpu or as a
 288  * last-ditch effort when memory seems to have run out.
 289  *
 290  * Returns:
 291  * The number of pages of backing storage actually released.
 292  */
 293 unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
 294 {
 295         unsigned long freed;
 296
 297         intel_runtime_pm_get(dev_priv);
 298         freed = i915_gem_shrink(dev_priv, -1UL, NULL,
 299                                 I915_SHRINK_BOUND |
 300                                 I915_SHRINK_UNBOUND |
 301                                 I915_SHRINK_ACTIVE);
 302         intel_runtime_pm_put(dev_priv);
 303
 304         return freed;
 305 }
 306
 307 static unsigned long
 308 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 309 {
 310         struct drm_i915_private *i915 =
 311                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 312         struct drm_i915_gem_object *obj;
 313         unsigned long num_objects = 0;
 314         unsigned long count = 0;
 315
 316         spin_lock(&i915->mm.obj_lock);
 317         list_for_each_entry(obj, &i915->mm.unbound_list, mm.link)
 318                 if (can_release_pages(obj)) {
 319                         count += obj->base.size >> PAGE_SHIFT;
 320                         num_objects++;
 321                 }
 322
 323         list_for_each_entry(obj, &i915->mm.bound_list, mm.link)
 324                 if (!i915_gem_object_is_active(obj) && can_release_pages(obj)) {
 325                         count += obj->base.size >> PAGE_SHIFT;
 326                         num_objects++;
 327                 }
 328         spin_unlock(&i915->mm.obj_lock);
 329
 330         /* Update our preferred vmscan batch size for the next pass.
 331          * Our rough guess for an effective batch size is roughly 2
 332          * available GEM objects worth of pages. That is we don't want
 333          * the shrinker to fire, until it is worth the cost of freeing an
 334          * entire GEM object.
 335          */
 336         if (num_objects) {
 337                 unsigned long avg = 2 * count / num_objects;
 338
 339                 i915->mm.shrinker.batch =
 340                         max((i915->mm.shrinker.batch + avg) >> 1,
 341                             128ul /* default SHRINK_BATCH */);
 342         }
 343
 344         return count;
 345 }
 346
 347 static unsigned long
 348 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 349 {
 350         struct drm_i915_private *dev_priv =
 351                 container_of(shrinker, struct drm_i915_private, mm.shrinker);
 352         unsigned long freed;
 353         bool unlock;
 354
 355         sc->nr_scanned = 0;
 356
 357         if (!shrinker_lock(dev_priv, &unlock))
 358                 return SHRINK_STOP;
 359
 360         freed = i915_gem_shrink(dev_priv,
 361                                 sc->nr_to_scan,
 362                                 &sc->nr_scanned,
 363                                 I915_SHRINK_BOUND |
 364                                 I915_SHRINK_UNBOUND |
 365                                 I915_SHRINK_PURGEABLE);
 366         if (freed < sc->nr_to_scan)
 367                 freed += i915_gem_shrink(dev_priv,
 368                                          sc->nr_to_scan - sc->nr_scanned,
 369                                          &sc->nr_scanned,
 370                                          I915_SHRINK_BOUND |
 371                                          I915_SHRINK_UNBOUND);
 372         if (freed < sc->nr_to_scan && current_is_kswapd()) {
 373                 intel_runtime_pm_get(dev_priv);
 374                 freed += i915_gem_shrink(dev_priv,
 375                                          sc->nr_to_scan - sc->nr_scanned,
 376                                          &sc->nr_scanned,
 377                                          I915_SHRINK_ACTIVE |
 378                                          I915_SHRINK_BOUND |
 379                                          I915_SHRINK_UNBOUND);
 380                 intel_runtime_pm_put(dev_priv);
 381         }
 382
 383         shrinker_unlock(dev_priv, unlock);
 384
 385         return sc->nr_scanned ? freed : SHRINK_STOP;
 386 }
 387
 388 static bool
 389 shrinker_lock_uninterruptible(struct drm_i915_private *dev_priv, bool *unlock,
 390                               int timeout_ms)
 391 {
 392         unsigned long timeout = jiffies + msecs_to_jiffies_timeout(timeout_ms);
 393
 394         do {
 395                 if (i915_gem_wait_for_idle(dev_priv, 0) == 0 &&
 396                     shrinker_lock(dev_priv, unlock))
 397                         break;
 398
 399                 schedule_timeout_killable(1);
 400                 if (fatal_signal_pending(current))
 401                         return false;
 402
 403                 if (time_after(jiffies, timeout)) {
 404                         pr_err("Unable to lock GPU to purge memory.\n");
 405                         return false;
 406                 }
 407         } while (1);
 408
 409         return true;
 410 }
 411
 412 static int
 413 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 414 {
 415         struct drm_i915_private *dev_priv =
 416                 container_of(nb, struct drm_i915_private, mm.oom_notifier);
 417         struct drm_i915_gem_object *obj;
 418         unsigned long unevictable, bound, unbound, freed_pages;
 419
 420         freed_pages = i915_gem_shrink_all(dev_priv);
 421
 422         /* Because we may be allocating inside our own driver, we cannot
 423          * assert that there are no objects with pinned pages that are not
 424          * being pointed to by hardware.
 425          */
 426         unbound = bound = unevictable = 0;
 427         spin_lock(&dev_priv->mm.obj_lock);
 428         list_for_each_entry(obj, &dev_priv->mm.unbound_list, mm.link) {
 429                 if (!can_release_pages(obj))
 430                         unevictable += obj->base.size >> PAGE_SHIFT;
 431                 else
 432                         unbound += obj->base.size >> PAGE_SHIFT;
 433         }
 434         list_for_each_entry(obj, &dev_priv->mm.bound_list, mm.link) {
 435                 if (!can_release_pages(obj))
 436                         unevictable += obj->base.size >> PAGE_SHIFT;
 437                 else
 438                         bound += obj->base.size >> PAGE_SHIFT;
 439         }
 440         spin_unlock(&dev_priv->mm.obj_lock);
 441
 442         if (freed_pages || unbound || bound)
 443                 pr_info("Purging GPU memory, %lu pages freed, "
 444                         "%lu pages still pinned.\n",
 445                         freed_pages, unevictable);
 446         if (unbound || bound)
 447                 pr_err("%lu and %lu pages still available in the "
 448                        "bound and unbound GPU page lists.\n",
 449                        bound, unbound);
 450
 451         *(unsigned long *)ptr += freed_pages;
 452         return NOTIFY_DONE;
 453 }
 454
 455 static int
 456 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 457 {
 458         struct drm_i915_private *dev_priv =
 459                 container_of(nb, struct drm_i915_private, mm.vmap_notifier);
 460         struct i915_vma *vma, *next;
 461         unsigned long freed_pages = 0;
 462         bool unlock;
 463         int ret;
 464
 465         if (!shrinker_lock_uninterruptible(dev_priv, &unlock, 5000))
 466                 return NOTIFY_DONE;
 467
 468         /* Force everything onto the inactive lists */
 469         ret = i915_gem_wait_for_idle(dev_priv, I915_WAIT_LOCKED);
 470         if (ret)
 471                 goto out;
 472
 473         intel_runtime_pm_get(dev_priv);
 474         freed_pages += i915_gem_shrink(dev_priv, -1UL, NULL,
 475                                        I915_SHRINK_BOUND |
 476                                        I915_SHRINK_UNBOUND |
 477                                        I915_SHRINK_ACTIVE |
 478                                        I915_SHRINK_VMAPS);
 479         intel_runtime_pm_put(dev_priv);
 480
 481         /* We also want to clear any cached iomaps as they wrap vmap */
 482         list_for_each_entry_safe(vma, next,
 483                                  &dev_priv->ggtt.base.inactive_list, vm_link) {
 484                 unsigned long count = vma->node.size >> PAGE_SHIFT;
 485                 if (vma->iomap && i915_vma_unbind(vma) == 0)
 486                         freed_pages += count;
 487         }
 488
 489 out:
 490         shrinker_unlock(dev_priv, unlock);
 491
 492         *(unsigned long *)ptr += freed_pages;
 493         return NOTIFY_DONE;
 494 }
 495
 496 /**
 497  * i915_gem_shrinker_init - Initialize i915 shrinker
 498  * @dev_priv: i915 device
 499  *
 500  * This function registers and sets up the i915 shrinker and OOM handler.
 501  */
 502 void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
 503 {
 504         dev_priv->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
 505         dev_priv->mm.shrinker.count_objects = i915_gem_shrinker_count;
 506         dev_priv->mm.shrinker.seeks = DEFAULT_SEEKS;
 507         dev_priv->mm.shrinker.batch = 4096;
 508         WARN_ON(register_shrinker(&dev_priv->mm.shrinker));
 509
 510         dev_priv->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 511         WARN_ON(register_oom_notifier(&dev_priv->mm.oom_notifier));
 512
 513         dev_priv->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
 514         WARN_ON(register_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
 515 }
 516
 517 /**
 518  * i915_gem_shrinker_cleanup - Clean up i915 shrinker
 519  * @dev_priv: i915 device
 520  *
 521  * This function unregisters the i915 shrinker and OOM handler.
 522  */
 523 void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv)
 524 {
 525         WARN_ON(unregister_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
 526         WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
 527         unregister_shrinker(&dev_priv->mm.shrinker);
 528 }