drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c

   1 // SPDX-License-Identifier: MIT
   2 /*
   3  * Copyright © 2014-2018 Intel Corporation
   4  */
   5
   6 #include "gem/i915_gem_object.h"
   7
   8 #include "i915_drv.h"
   9 #include "intel_engine_pm.h"
  10 #include "intel_gt_buffer_pool.h"
  11
  12 static struct intel_gt *to_gt(struct intel_gt_buffer_pool *pool)
  13 {
  14         return container_of(pool, struct intel_gt, buffer_pool);
  15 }
  16
  17 static struct list_head *
  18 bucket_for_size(struct intel_gt_buffer_pool *pool, size_t sz)
  19 {
  20         int n;
  21
  22         /*
  23          * Compute a power-of-two bucket, but throw everything greater than
  24          * 16KiB into the same bucket: i.e. the buckets hold objects of
  25          * (1 page, 2 pages, 4 pages, 8+ pages).
  26          */
  27         n = fls(sz >> PAGE_SHIFT) - 1;
  28         if (n >= ARRAY_SIZE(pool->cache_list))
  29                 n = ARRAY_SIZE(pool->cache_list) - 1;
  30
  31         return &pool->cache_list[n];
  32 }
  33
  34 static void node_free(struct intel_gt_buffer_pool_node *node)
  35 {
  36         i915_gem_object_put(node->obj);
  37         i915_active_fini(&node->active);
  38         kfree_rcu(node, rcu);
  39 }
  40
  41 static bool pool_free_older_than(struct intel_gt_buffer_pool *pool, long keep)
  42 {
  43         struct intel_gt_buffer_pool_node *node, *stale = NULL;
  44         bool active = false;
  45         int n;
  46
  47         /* Free buffers that have not been used in the past second */
  48         for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
  49                 struct list_head *list = &pool->cache_list[n];
  50
  51                 if (list_empty(list))
  52                         continue;
  53
  54                 if (spin_trylock_irq(&pool->lock)) {
  55                         struct list_head *pos;
  56
  57                         /* Most recent at head; oldest at tail */
  58                         list_for_each_prev(pos, list) {
  59                                 unsigned long age;
  60
  61                                 node = list_entry(pos, typeof(*node), link);
  62
  63                                 age = READ_ONCE(node->age);
  64                                 if (!age || jiffies - age < keep)
  65                                         break;
  66
  67                                 /* Check we are the first to claim this node */
  68                                 if (!xchg(&node->age, 0))
  69                                         break;
  70
  71                                 node->free = stale;
  72                                 stale = node;
  73                         }
  74                         if (!list_is_last(pos, list))
  75                                 __list_del_many(pos, list);
  76
  77                         spin_unlock_irq(&pool->lock);
  78                 }
  79
  80                 active |= !list_empty(list);
  81         }
  82
  83         while ((node = stale)) {
  84                 stale = stale->free;
  85                 node_free(node);
  86         }
  87
  88         return active;
  89 }
  90
  91 static void pool_free_work(struct work_struct *wrk)
  92 {
  93         struct intel_gt_buffer_pool *pool =
  94                 container_of(wrk, typeof(*pool), work.work);
  95
  96         if (pool_free_older_than(pool, HZ))
  97                 schedule_delayed_work(&pool->work,
  98                                       round_jiffies_up_relative(HZ));
  99 }
 100
 101 static int pool_active(struct i915_active *ref)
 102 {
 103         struct intel_gt_buffer_pool_node *node =
 104                 container_of(ref, typeof(*node), active);
 105         struct dma_resv *resv = node->obj->base.resv;
 106         int err;
 107
 108         if (dma_resv_trylock(resv)) {
 109                 dma_resv_add_excl_fence(resv, NULL);
 110                 dma_resv_unlock(resv);
 111         }
 112
 113         err = i915_gem_object_pin_pages(node->obj);
 114         if (err)
 115                 return err;
 116
 117         /* Hide this pinned object from the shrinker until retired */
 118         i915_gem_object_make_unshrinkable(node->obj);
 119
 120         return 0;
 121 }
 122
 123 __i915_active_call
 124 static void pool_retire(struct i915_active *ref)
 125 {
 126         struct intel_gt_buffer_pool_node *node =
 127                 container_of(ref, typeof(*node), active);
 128         struct intel_gt_buffer_pool *pool = node->pool;
 129         struct list_head *list = bucket_for_size(pool, node->obj->base.size);
 130         unsigned long flags;
 131
 132         i915_gem_object_unpin_pages(node->obj);
 133
 134         /* Return this object to the shrinker pool */
 135         i915_gem_object_make_purgeable(node->obj);
 136
 137         GEM_BUG_ON(node->age);
 138         spin_lock_irqsave(&pool->lock, flags);
 139         list_add_rcu(&node->link, list);
 140         WRITE_ONCE(node->age, jiffies ?: 1); /* 0 reserved for active nodes */
 141         spin_unlock_irqrestore(&pool->lock, flags);
 142
 143         schedule_delayed_work(&pool->work,
 144                               round_jiffies_up_relative(HZ));
 145 }
 146
 147 static struct intel_gt_buffer_pool_node *
 148 node_create(struct intel_gt_buffer_pool *pool, size_t sz)
 149 {
 150         struct intel_gt *gt = to_gt(pool);
 151         struct intel_gt_buffer_pool_node *node;
 152         struct drm_i915_gem_object *obj;
 153
 154         node = kmalloc(sizeof(*node),
 155                        GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
 156         if (!node)
 157                 return ERR_PTR(-ENOMEM);
 158
 159         node->age = 0;
 160         node->pool = pool;
 161         i915_active_init(&node->active, pool_active, pool_retire);
 162
 163         obj = i915_gem_object_create_internal(gt->i915, sz);
 164         if (IS_ERR(obj)) {
 165                 i915_active_fini(&node->active);
 166                 kfree(node);
 167                 return ERR_CAST(obj);
 168         }
 169
 170         i915_gem_object_set_readonly(obj);
 171
 172         node->obj = obj;
 173         return node;
 174 }
 175
 176 struct intel_gt_buffer_pool_node *
 177 intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size)
 178 {
 179         struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 180         struct intel_gt_buffer_pool_node *node;
 181         struct list_head *list;
 182         int ret;
 183
 184         size = PAGE_ALIGN(size);
 185         list = bucket_for_size(pool, size);
 186
 187         rcu_read_lock();
 188         list_for_each_entry_rcu(node, list, link) {
 189                 unsigned long age;
 190
 191                 if (node->obj->base.size < size)
 192                         continue;
 193
 194                 age = READ_ONCE(node->age);
 195                 if (!age)
 196                         continue;
 197
 198                 if (cmpxchg(&node->age, age, 0) == age) {
 199                         spin_lock_irq(&pool->lock);
 200                         list_del_rcu(&node->link);
 201                         spin_unlock_irq(&pool->lock);
 202                         break;
 203                 }
 204         }
 205         rcu_read_unlock();
 206
 207         if (&node->link == list) {
 208                 node = node_create(pool, size);
 209                 if (IS_ERR(node))
 210                         return node;
 211         }
 212
 213         ret = i915_active_acquire(&node->active);
 214         if (ret) {
 215                 node_free(node);
 216                 return ERR_PTR(ret);
 217         }
 218
 219         return node;
 220 }
 221
 222 void intel_gt_init_buffer_pool(struct intel_gt *gt)
 223 {
 224         struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 225         int n;
 226
 227         spin_lock_init(&pool->lock);
 228         for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
 229                 INIT_LIST_HEAD(&pool->cache_list[n]);
 230         INIT_DELAYED_WORK(&pool->work, pool_free_work);
 231 }
 232
 233 void intel_gt_flush_buffer_pool(struct intel_gt *gt)
 234 {
 235         struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 236
 237         do {
 238                 while (pool_free_older_than(pool, 0))
 239                         ;
 240         } while (cancel_delayed_work_sync(&pool->work));
 241 }
 242
 243 void intel_gt_fini_buffer_pool(struct intel_gt *gt)
 244 {
 245         struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 246         int n;
 247
 248         intel_gt_flush_buffer_pool(gt);
 249
 250         for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
 251                 GEM_BUG_ON(!list_empty(&pool->cache_list[n]));
 252 }