OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​i915/​gem/​i915_gem_shrinker.c	Source navigation Diff markup Identifier search General search
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 /*
  * SPDX-License-Identifier: MIT
  *
  * Copyright © 2008-2015 Intel Corporation
  */
 
 #include <linux/oom.h>
 #include <linux/sched/mm.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/pci.h>
 #include <linux/dma-buf.h>
 #include <linux/vmalloc.h>
 
 #include "gt/intel_gt_requests.h"
 
 #include "i915_trace.h"
 
 static bool swap_available(void)
 {
     return get_nr_swap_pages() > 0;
 }
 
 static bool can_release_pages(struct drm_i915_gem_object *obj)
 {
     /* Consider only shrinkable ojects. */
     if (!i915_gem_object_is_shrinkable(obj))
         return false;
 
     /*
      * We can only return physical pages to the system if we can either
      * discard the contents (because the user has marked them as being
      * purgeable) or if we can move their contents out to swap.
      */
     return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
 }
 
 static bool drop_pages(struct drm_i915_gem_object *obj,
                unsigned long shrink, bool trylock_vm)
 {
     unsigned long flags;
 
     flags = 0;
     if (shrink & I915_SHRINK_ACTIVE)
         flags |= I915_GEM_OBJECT_UNBIND_ACTIVE;
     if (!(shrink & I915_SHRINK_BOUND))
         flags |= I915_GEM_OBJECT_UNBIND_TEST;
     if (trylock_vm)
         flags |= I915_GEM_OBJECT_UNBIND_VM_TRYLOCK;
 
     if (i915_gem_object_unbind(obj, flags) == 0)
         return true;
 
     return false;
 }
 
 static int try_to_writeback(struct drm_i915_gem_object *obj, unsigned int flags)
 {
     if (obj->ops->shrink) {
         unsigned int shrink_flags = 0;
 
         if (!(flags & I915_SHRINK_ACTIVE))
             shrink_flags |= I915_GEM_OBJECT_SHRINK_NO_GPU_WAIT;
 
         if (flags & I915_SHRINK_WRITEBACK)
             shrink_flags |= I915_GEM_OBJECT_SHRINK_WRITEBACK;
 
         return obj->ops->shrink(obj, shrink_flags);
     }
 
     return 0;
 }
 
 /**
  * i915_gem_shrink - Shrink buffer object caches
  * @ww: i915 gem ww acquire ctx, or NULL
  * @i915: i915 device
  * @target: amount of memory to make available, in pages
  * @nr_scanned: optional output for number of pages scanned (incremental)
  * @shrink: control flags for selecting cache types
  *
  * This function is the main interface to the shrinker. It will try to release
  * up to @target pages of main memory backing storage from buffer objects.
  * Selection of the specific caches can be done with @flags. This is e.g. useful
  * when purgeable objects should be removed from caches preferentially.
  *
  * Note that it's not guaranteed that released amount is actually available as
  * free system memory - the pages might still be in-used to due to other reasons
  * (like cpu mmaps) or the mm core has reused them before we could grab them.
  * Therefore code that needs to explicitly shrink buffer objects caches (e.g. to
  * avoid deadlocks in memory reclaim) must fall back to i915_gem_shrink_all().
  *
  * Also note that any kind of pinning (both per-vma address space pins and
  * backing storage pins at the buffer object level) result in the shrinker code
  * having to skip the object.
  *
  * Returns:
  * The number of pages of backing storage actually released.
  */
 unsigned long
 i915_gem_shrink(struct i915_gem_ww_ctx *ww,
         struct drm_i915_private *i915,
         unsigned long target,
         unsigned long *nr_scanned,
         unsigned int shrink)
 {
     const struct {
         struct list_head *list;
         unsigned int bit;
     } phases[] = {
         { &i915->mm.purge_list, ~0u },
         {
             &i915->mm.shrink_list,
             I915_SHRINK_BOUND | I915_SHRINK_UNBOUND
         },
         { NULL, 0 },
     }, *phase;
     intel_wakeref_t wakeref = 0;
     unsigned long count = 0;
     unsigned long scanned = 0;
     int err = 0;
 
     /* CHV + VTD workaround use stop_machine(); need to trylock vm->mutex */
     bool trylock_vm = !ww && intel_vm_no_concurrent_access_wa(i915);
 
     trace_i915_gem_shrink(i915, target, shrink);
 
     /*
      * Unbinding of objects will require HW access; Let us not wake the
      * device just to recover a little memory. If absolutely necessary,
      * we will force the wake during oom-notifier.
      */
     if (shrink & I915_SHRINK_BOUND) {
         wakeref = intel_runtime_pm_get_if_in_use(&i915->runtime_pm);
         if (!wakeref)
             shrink &= ~I915_SHRINK_BOUND;
     }
 
     /*
      * When shrinking the active list, we should also consider active
      * contexts. Active contexts are pinned until they are retired, and
      * so can not be simply unbound to retire and unpin their pages. To
      * shrink the contexts, we must wait until the gpu is idle and
      * completed its switch to the kernel context. In short, we do
      * not have a good mechanism for idling a specific context, but
      * what we can do is give them a kick so that we do not keep idle
      * contexts around longer than is necessary.
      */
     if (shrink & I915_SHRINK_ACTIVE)
         /* Retire requests to unpin all idle contexts */
         intel_gt_retire_requests(to_gt(i915));
 
     /*
      * As we may completely rewrite the (un)bound list whilst unbinding
      * (due to retiring requests) we have to strictly process only
      * one element of the list at the time, and recheck the list
      * on every iteration.
      *
      * In particular, we must hold a reference whilst removing the
      * object as we may end up waiting for and/or retiring the objects.
      * This might release the final reference (held by the active list)
      * and result in the object being freed from under us. This is
      * similar to the precautions the eviction code must take whilst
      * removing objects.
      *
      * Also note that although these lists do not hold a reference to
      * the object we can safely grab one here: The final object
      * unreferencing and the bound_list are both protected by the
      * dev->struct_mutex and so we won't ever be able to observe an
      * object on the bound_list with a reference count equals 0.
      */
     for (phase = phases; phase->list; phase++) {
         struct list_head still_in_list;
         struct drm_i915_gem_object *obj;
         unsigned long flags;
 
         if ((shrink & phase->bit) == 0)
             continue;
 
         INIT_LIST_HEAD(&still_in_list);
 
         /*
          * We serialize our access to unreferenced objects through
          * the use of the struct_mutex. While the objects are not
          * yet freed (due to RCU then a workqueue) we still want
          * to be able to shrink their pages, so they remain on
          * the unbound/bound list until actually freed.
          */
         spin_lock_irqsave(&i915->mm.obj_lock, flags);
         while (count < target &&
                (obj = list_first_entry_or_null(phase->list,
                                typeof(*obj),
                                mm.link))) {
             list_move_tail(&obj->mm.link, &still_in_list);
 
             if (shrink & I915_SHRINK_VMAPS &&
                 !is_vmalloc_addr(obj->mm.mapping))
                 continue;
 
             if (!(shrink & I915_SHRINK_ACTIVE) &&
                 i915_gem_object_is_framebuffer(obj))
                 continue;
 
             if (!can_release_pages(obj))
                 continue;
 
             if (!kref_get_unless_zero(&obj->base.refcount))
                 continue;
 
             spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
             /* May arrive from get_pages on another bo */
             if (!ww) {
                 if (!i915_gem_object_trylock(obj, NULL))
                     goto skip;
             } else {
                 err = i915_gem_object_lock(obj, ww);
                 if (err)
                     goto skip;
             }
 
             if (drop_pages(obj, shrink, trylock_vm) &&
                 !__i915_gem_object_put_pages(obj) &&
                 !try_to_writeback(obj, shrink))
                 count += obj->base.size >> PAGE_SHIFT;
 
             if (!ww)
                 i915_gem_object_unlock(obj);
 
             scanned += obj->base.size >> PAGE_SHIFT;
 skip:
             i915_gem_object_put(obj);
 
             spin_lock_irqsave(&i915->mm.obj_lock, flags);
             if (err)
                 break;
         }
         list_splice_tail(&still_in_list, phase->list);
         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
         if (err)
             break;
     }
 
     if (shrink & I915_SHRINK_BOUND)
         intel_runtime_pm_put(&i915->runtime_pm, wakeref);
 
     if (err)
         return err;
 
     if (nr_scanned)
         *nr_scanned += scanned;
     return count;
 }
 
 /**
  * i915_gem_shrink_all - Shrink buffer object caches completely
  * @i915: i915 device
  *
  * This is a simple wraper around i915_gem_shrink() to aggressively shrink all
  * caches completely. It also first waits for and retires all outstanding
  * requests to also be able to release backing storage for active objects.
  *
  * This should only be used in code to intentionally quiescent the gpu or as a
  * last-ditch effort when memory seems to have run out.
  *
  * Returns:
  * The number of pages of backing storage actually released.
  */
 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915)
 {
     intel_wakeref_t wakeref;
     unsigned long freed = 0;
 
     with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
         freed = i915_gem_shrink(NULL, i915, -1UL, NULL,
                     I915_SHRINK_BOUND |
                     I915_SHRINK_UNBOUND);
     }
 
     return freed;
 }
 
 static unsigned long
 i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
     struct drm_i915_private *i915 =
         container_of(shrinker, struct drm_i915_private, mm.shrinker);
     unsigned long num_objects;
     unsigned long count;
 
     count = READ_ONCE(i915->mm.shrink_memory) >> PAGE_SHIFT;
     num_objects = READ_ONCE(i915->mm.shrink_count);
 
     /*
      * Update our preferred vmscan batch size for the next pass.
      * Our rough guess for an effective batch size is roughly 2
      * available GEM objects worth of pages. That is we don't want
      * the shrinker to fire, until it is worth the cost of freeing an
      * entire GEM object.
      */
     if (num_objects) {
         unsigned long avg = 2 * count / num_objects;
 
         i915->mm.shrinker.batch =
             max((i915->mm.shrinker.batch + avg) >> 1,
                 128ul /* default SHRINK_BATCH */);
     }
 
     return count;
 }
 
 static unsigned long
 i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 {
     struct drm_i915_private *i915 =
         container_of(shrinker, struct drm_i915_private, mm.shrinker);
     unsigned long freed;
 
     sc->nr_scanned = 0;
 
     freed = i915_gem_shrink(NULL, i915,
                 sc->nr_to_scan,
                 &sc->nr_scanned,
                 I915_SHRINK_BOUND |
                 I915_SHRINK_UNBOUND);
     if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
         intel_wakeref_t wakeref;
 
         with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
             freed += i915_gem_shrink(NULL, i915,
                          sc->nr_to_scan - sc->nr_scanned,
                          &sc->nr_scanned,
                          I915_SHRINK_ACTIVE |
                          I915_SHRINK_BOUND |
                          I915_SHRINK_UNBOUND |
                          I915_SHRINK_WRITEBACK);
         }
     }
 
     return sc->nr_scanned ? freed : SHRINK_STOP;
 }
 
 static int
 i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 {
     struct drm_i915_private *i915 =
         container_of(nb, struct drm_i915_private, mm.oom_notifier);
     struct drm_i915_gem_object *obj;
     unsigned long unevictable, available, freed_pages;
     intel_wakeref_t wakeref;
     unsigned long flags;
 
     freed_pages = 0;
     with_intel_runtime_pm(&i915->runtime_pm, wakeref)
         freed_pages += i915_gem_shrink(NULL, i915, -1UL, NULL,
                            I915_SHRINK_BOUND |
                            I915_SHRINK_UNBOUND |
                            I915_SHRINK_WRITEBACK);
 
     /* Because we may be allocating inside our own driver, we cannot
      * assert that there are no objects with pinned pages that are not
      * being pointed to by hardware.
      */
     available = unevictable = 0;
     spin_lock_irqsave(&i915->mm.obj_lock, flags);
     list_for_each_entry(obj, &i915->mm.shrink_list, mm.link) {
         if (!can_release_pages(obj))
             unevictable += obj->base.size >> PAGE_SHIFT;
         else
             available += obj->base.size >> PAGE_SHIFT;
     }
     spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 
     if (freed_pages || available)
         pr_info("Purging GPU memory, %lu pages freed, "
             "%lu pages still pinned, %lu pages left available.\n",
             freed_pages, unevictable, available);
 
     *(unsigned long *)ptr += freed_pages;
     return NOTIFY_DONE;
 }
 
 static int
 i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
 {
     struct drm_i915_private *i915 =
         container_of(nb, struct drm_i915_private, mm.vmap_notifier);
     struct i915_vma *vma, *next;
     unsigned long freed_pages = 0;
     intel_wakeref_t wakeref;
 
     with_intel_runtime_pm(&i915->runtime_pm, wakeref)
         freed_pages += i915_gem_shrink(NULL, i915, -1UL, NULL,
                            I915_SHRINK_BOUND |
                            I915_SHRINK_UNBOUND |
                            I915_SHRINK_VMAPS);
 
     /* We also want to clear any cached iomaps as they wrap vmap */
     mutex_lock(&to_gt(i915)->ggtt->vm.mutex);
     list_for_each_entry_safe(vma, next,
                  &to_gt(i915)->ggtt->vm.bound_list, vm_link) {
         unsigned long count = vma->node.size >> PAGE_SHIFT;
         struct drm_i915_gem_object *obj = vma->obj;
 
         if (!vma->iomap || i915_vma_is_active(vma))
             continue;
 
         if (!i915_gem_object_trylock(obj, NULL))
             continue;
 
         if (__i915_vma_unbind(vma) == 0)
             freed_pages += count;
 
         i915_gem_object_unlock(obj);
     }
     mutex_unlock(&to_gt(i915)->ggtt->vm.mutex);
 
     *(unsigned long *)ptr += freed_pages;
     return NOTIFY_DONE;
 }
 
 void i915_gem_driver_register__shrinker(struct drm_i915_private *i915)
 {
     i915->mm.shrinker.scan_objects = i915_gem_shrinker_scan;
     i915->mm.shrinker.count_objects = i915_gem_shrinker_count;
     i915->mm.shrinker.seeks = DEFAULT_SEEKS;
     i915->mm.shrinker.batch = 4096;
     drm_WARN_ON(&i915->drm, register_shrinker(&i915->mm.shrinker,
                           "drm-i915_gem"));
 
     i915->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
     drm_WARN_ON(&i915->drm, register_oom_notifier(&i915->mm.oom_notifier));
 
     i915->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
     drm_WARN_ON(&i915->drm,
             register_vmap_purge_notifier(&i915->mm.vmap_notifier));
 }
 
 void i915_gem_driver_unregister__shrinker(struct drm_i915_private *i915)
 {
     drm_WARN_ON(&i915->drm,
             unregister_vmap_purge_notifier(&i915->mm.vmap_notifier));
     drm_WARN_ON(&i915->drm,
             unregister_oom_notifier(&i915->mm.oom_notifier));
     unregister_shrinker(&i915->mm.shrinker);
 }
 
 void i915_gem_shrinker_taints_mutex(struct drm_i915_private *i915,
                     struct mutex *mutex)
 {
     if (!IS_ENABLED(CONFIG_LOCKDEP))
         return;
 
     fs_reclaim_acquire(GFP_KERNEL);
 
     mutex_acquire(&mutex->dep_map, 0, 0, _RET_IP_);
     mutex_release(&mutex->dep_map, _RET_IP_);
 
     fs_reclaim_release(GFP_KERNEL);
 }
 
 #define obj_to_i915(obj__) to_i915((obj__)->base.dev)
 
 /**
  * i915_gem_object_make_unshrinkable - Hide the object from the shrinker. By
  * default all object types that support shrinking(see IS_SHRINKABLE), will also
  * make the object visible to the shrinker after allocating the system memory
  * pages.
  * @obj: The GEM object.
  *
  * This is typically used for special kernel internal objects that can't be
  * easily processed by the shrinker, like if they are perma-pinned.
  */
 void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj)
 {
     struct drm_i915_private *i915 = obj_to_i915(obj);
     unsigned long flags;
 
     /*
      * We can only be called while the pages are pinned or when
      * the pages are released. If pinned, we should only be called
      * from a single caller under controlled conditions; and on release
      * only one caller may release us. Neither the two may cross.
      */
     if (atomic_add_unless(&obj->mm.shrink_pin, 1, 0))
         return;
 
     spin_lock_irqsave(&i915->mm.obj_lock, flags);
     if (!atomic_fetch_inc(&obj->mm.shrink_pin) &&
         !list_empty(&obj->mm.link)) {
         list_del_init(&obj->mm.link);
         i915->mm.shrink_count--;
         i915->mm.shrink_memory -= obj->base.size;
     }
     spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 }
 
 static void ___i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj,
                            struct list_head *head)
 {
     struct drm_i915_private *i915 = obj_to_i915(obj);
     unsigned long flags;
 
     if (!i915_gem_object_is_shrinkable(obj))
         return;
 
     if (atomic_add_unless(&obj->mm.shrink_pin, -1, 1))
         return;
 
     spin_lock_irqsave(&i915->mm.obj_lock, flags);
     GEM_BUG_ON(!kref_read(&obj->base.refcount));
     if (atomic_dec_and_test(&obj->mm.shrink_pin)) {
         GEM_BUG_ON(!list_empty(&obj->mm.link));
 
         list_add_tail(&obj->mm.link, head);
         i915->mm.shrink_count++;
         i915->mm.shrink_memory += obj->base.size;
 
     }
     spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 }
 
 /**
  * __i915_gem_object_make_shrinkable - Move the object to the tail of the
  * shrinkable list. Objects on this list might be swapped out. Used with
  * WILLNEED objects.
  * @obj: The GEM object.
  *
  * DO NOT USE. This is intended to be called on very special objects that don't
  * yet have mm.pages, but are guaranteed to have potentially reclaimable pages
  * underneath.
  */
 void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 {
     ___i915_gem_object_make_shrinkable(obj,
                        &obj_to_i915(obj)->mm.shrink_list);
 }
 
 /**
  * __i915_gem_object_make_purgeable - Move the object to the tail of the
  * purgeable list. Objects on this list might be swapped out. Used with
  * DONTNEED objects.
  * @obj: The GEM object.
  *
  * DO NOT USE. This is intended to be called on very special objects that don't
  * yet have mm.pages, but are guaranteed to have potentially reclaimable pages
  * underneath.
  */
 void __i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 {
     ___i915_gem_object_make_shrinkable(obj,
                        &obj_to_i915(obj)->mm.purge_list);
 }
 
 /**
  * i915_gem_object_make_shrinkable - Move the object to the tail of the
  * shrinkable list. Objects on this list might be swapped out. Used with
  * WILLNEED objects.
  * @obj: The GEM object.
  *
  * MUST only be called on objects which have backing pages.
  *
  * MUST be balanced with previous call to i915_gem_object_make_unshrinkable().
  */
 void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj)
 {
     GEM_BUG_ON(!i915_gem_object_has_pages(obj));
     __i915_gem_object_make_shrinkable(obj);
 }
 
 /**
  * i915_gem_object_make_purgeable - Move the object to the tail of the purgeable
  * list. Used with DONTNEED objects. Unlike with shrinkable objects, the
  * shrinker will attempt to discard the backing pages, instead of trying to swap
  * them out.
  * @obj: The GEM object.
  *
  * MUST only be called on objects which have backing pages.
  *
  * MUST be balanced with previous call to i915_gem_object_make_unshrinkable().
  */
 void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj)
 {
     GEM_BUG_ON(!i915_gem_object_has_pages(obj));
     __i915_gem_object_make_purgeable(obj);
 }

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