drivers/gpu/drm/i915/i915_active.c

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2019 Intel Corporation
   5  */
   6
   7 #include "gt/intel_engine_pm.h"
   8
   9 #include "i915_drv.h"
  10 #include "i915_active.h"
  11 #include "i915_globals.h"
  12
  13 #define BKL(ref) (&(ref)->i915->drm.struct_mutex)
  14
  15 /*
  16  * Active refs memory management
  17  *
  18  * To be more economical with memory, we reap all the i915_active trees as
  19  * they idle (when we know the active requests are inactive) and allocate the
  20  * nodes from a local slab cache to hopefully reduce the fragmentation.
  21  */
  22 static struct i915_global_active {
  23         struct i915_global base;
  24         struct kmem_cache *slab_cache;
  25 } global;
  26
  27 struct active_node {
  28         struct i915_active_request base;
  29         struct i915_active *ref;
  30         struct rb_node node;
  31         u64 timeline;
  32 };
  33
  34 static void
  35 __active_park(struct i915_active *ref)
  36 {
  37         struct active_node *it, *n;
  38
  39         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
  40                 GEM_BUG_ON(i915_active_request_isset(&it->base));
  41                 kmem_cache_free(global.slab_cache, it);
  42         }
  43         ref->tree = RB_ROOT;
  44 }
  45
  46 static void
  47 __active_retire(struct i915_active *ref)
  48 {
  49         GEM_BUG_ON(!ref->count);
  50         if (--ref->count)
  51                 return;
  52
  53         /* return the unused nodes to our slabcache */
  54         __active_park(ref);
  55
  56         ref->retire(ref);
  57 }
  58
  59 static void
  60 node_retire(struct i915_active_request *base, struct i915_request *rq)
  61 {
  62         __active_retire(container_of(base, struct active_node, base)->ref);
  63 }
  64
  65 static void
  66 last_retire(struct i915_active_request *base, struct i915_request *rq)
  67 {
  68         __active_retire(container_of(base, struct i915_active, last));
  69 }
  70
  71 static struct i915_active_request *
  72 active_instance(struct i915_active *ref, u64 idx)
  73 {
  74         struct active_node *node;
  75         struct rb_node **p, *parent;
  76         struct i915_request *old;
  77
  78         /*
  79          * We track the most recently used timeline to skip a rbtree search
  80          * for the common case, under typical loads we never need the rbtree
  81          * at all. We can reuse the last slot if it is empty, that is
  82          * after the previous activity has been retired, or if it matches the
  83          * current timeline.
  84          *
  85          * Note that we allow the timeline to be active simultaneously in
  86          * the rbtree and the last cache. We do this to avoid having
  87          * to search and replace the rbtree element for a new timeline, with
  88          * the cost being that we must be aware that the ref may be retired
  89          * twice for the same timeline (as the older rbtree element will be
  90          * retired before the new request added to last).
  91          */
  92         old = i915_active_request_raw(&ref->last, BKL(ref));
  93         if (!old || old->fence.context == idx)
  94                 goto out;
  95
  96         /* Move the currently active fence into the rbtree */
  97         idx = old->fence.context;
  98
  99         parent = NULL;
 100         p = &ref->tree.rb_node;
 101         while (*p) {
 102                 parent = *p;
 103
 104                 node = rb_entry(parent, struct active_node, node);
 105                 if (node->timeline == idx)
 106                         goto replace;
 107
 108                 if (node->timeline < idx)
 109                         p = &parent->rb_right;
 110                 else
 111                         p = &parent->rb_left;
 112         }
 113
 114         node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
 115
 116         /* kmalloc may retire the ref->last (thanks shrinker)! */
 117         if (unlikely(!i915_active_request_raw(&ref->last, BKL(ref)))) {
 118                 kmem_cache_free(global.slab_cache, node);
 119                 goto out;
 120         }
 121
 122         if (unlikely(!node))
 123                 return ERR_PTR(-ENOMEM);
 124
 125         i915_active_request_init(&node->base, NULL, node_retire);
 126         node->ref = ref;
 127         node->timeline = idx;
 128
 129         rb_link_node(&node->node, parent, p);
 130         rb_insert_color(&node->node, &ref->tree);
 131
 132 replace:
 133         /*
 134          * Overwrite the previous active slot in the rbtree with last,
 135          * leaving last zeroed. If the previous slot is still active,
 136          * we must be careful as we now only expect to receive one retire
 137          * callback not two, and so much undo the active counting for the
 138          * overwritten slot.
 139          */
 140         if (i915_active_request_isset(&node->base)) {
 141                 /* Retire ourselves from the old rq->active_list */
 142                 __list_del_entry(&node->base.link);
 143                 ref->count--;
 144                 GEM_BUG_ON(!ref->count);
 145         }
 146         GEM_BUG_ON(list_empty(&ref->last.link));
 147         list_replace_init(&ref->last.link, &node->base.link);
 148         node->base.request = fetch_and_zero(&ref->last.request);
 149
 150 out:
 151         return &ref->last;
 152 }
 153
 154 void i915_active_init(struct drm_i915_private *i915,
 155                       struct i915_active *ref,
 156                       void (*retire)(struct i915_active *ref))
 157 {
 158         ref->i915 = i915;
 159         ref->retire = retire;
 160         ref->tree = RB_ROOT;
 161         i915_active_request_init(&ref->last, NULL, last_retire);
 162         init_llist_head(&ref->barriers);
 163         ref->count = 0;
 164 }
 165
 166 int i915_active_ref(struct i915_active *ref,
 167                     u64 timeline,
 168                     struct i915_request *rq)
 169 {
 170         struct i915_active_request *active;
 171         int err = 0;
 172
 173         /* Prevent reaping in case we malloc/wait while building the tree */
 174         i915_active_acquire(ref);
 175
 176         active = active_instance(ref, timeline);
 177         if (IS_ERR(active)) {
 178                 err = PTR_ERR(active);
 179                 goto out;
 180         }
 181
 182         if (!i915_active_request_isset(active))
 183                 ref->count++;
 184         __i915_active_request_set(active, rq);
 185
 186         GEM_BUG_ON(!ref->count);
 187 out:
 188         i915_active_release(ref);
 189         return err;
 190 }
 191
 192 bool i915_active_acquire(struct i915_active *ref)
 193 {
 194         lockdep_assert_held(BKL(ref));
 195         return !ref->count++;
 196 }
 197
 198 void i915_active_release(struct i915_active *ref)
 199 {
 200         lockdep_assert_held(BKL(ref));
 201         __active_retire(ref);
 202 }
 203
 204 int i915_active_wait(struct i915_active *ref)
 205 {
 206         struct active_node *it, *n;
 207         int ret = 0;
 208
 209         if (i915_active_acquire(ref))
 210                 goto out_release;
 211
 212         ret = i915_active_request_retire(&ref->last, BKL(ref));
 213         if (ret)
 214                 goto out_release;
 215
 216         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 217                 ret = i915_active_request_retire(&it->base, BKL(ref));
 218                 if (ret)
 219                         break;
 220         }
 221
 222 out_release:
 223         i915_active_release(ref);
 224         return ret;
 225 }
 226
 227 int i915_request_await_active_request(struct i915_request *rq,
 228                                       struct i915_active_request *active)
 229 {
 230         struct i915_request *barrier =
 231                 i915_active_request_raw(active, &rq->i915->drm.struct_mutex);
 232
 233         return barrier ? i915_request_await_dma_fence(rq, &barrier->fence) : 0;
 234 }
 235
 236 int i915_request_await_active(struct i915_request *rq, struct i915_active *ref)
 237 {
 238         struct active_node *it, *n;
 239         int err = 0;
 240
 241         /* await allocates and so we need to avoid hitting the shrinker */
 242         if (i915_active_acquire(ref))
 243                 goto out; /* was idle */
 244
 245         err = i915_request_await_active_request(rq, &ref->last);
 246         if (err)
 247                 goto out;
 248
 249         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 250                 err = i915_request_await_active_request(rq, &it->base);
 251                 if (err)
 252                         goto out;
 253         }
 254
 255 out:
 256         i915_active_release(ref);
 257         return err;
 258 }
 259
 260 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
 261 void i915_active_fini(struct i915_active *ref)
 262 {
 263         GEM_BUG_ON(i915_active_request_isset(&ref->last));
 264         GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
 265         GEM_BUG_ON(ref->count);
 266 }
 267 #endif
 268
 269 int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 270                                             struct intel_engine_cs *engine)
 271 {
 272         struct drm_i915_private *i915 = engine->i915;
 273         struct llist_node *pos, *next;
 274         unsigned long tmp;
 275         int err;
 276
 277         GEM_BUG_ON(!engine->mask);
 278         for_each_engine_masked(engine, i915, engine->mask, tmp) {
 279                 struct intel_context *kctx = engine->kernel_context;
 280                 struct active_node *node;
 281
 282                 node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
 283                 if (unlikely(!node)) {
 284                         err = -ENOMEM;
 285                         goto unwind;
 286                 }
 287
 288                 i915_active_request_init(&node->base,
 289                                          (void *)engine, node_retire);
 290                 node->timeline = kctx->ring->timeline->fence_context;
 291                 node->ref = ref;
 292                 ref->count++;
 293
 294                 intel_engine_pm_get(engine);
 295                 llist_add((struct llist_node *)&node->base.link,
 296                           &ref->barriers);
 297         }
 298
 299         return 0;
 300
 301 unwind:
 302         llist_for_each_safe(pos, next, llist_del_all(&ref->barriers)) {
 303                 struct active_node *node;
 304
 305                 node = container_of((struct list_head *)pos,
 306                                     typeof(*node), base.link);
 307                 engine = (void *)rcu_access_pointer(node->base.request);
 308
 309                 intel_engine_pm_put(engine);
 310                 kmem_cache_free(global.slab_cache, node);
 311         }
 312         return err;
 313 }
 314
 315 void i915_active_acquire_barrier(struct i915_active *ref)
 316 {
 317         struct llist_node *pos, *next;
 318
 319         i915_active_acquire(ref);
 320
 321         llist_for_each_safe(pos, next, llist_del_all(&ref->barriers)) {
 322                 struct intel_engine_cs *engine;
 323                 struct active_node *node;
 324                 struct rb_node **p, *parent;
 325
 326                 node = container_of((struct list_head *)pos,
 327                                     typeof(*node), base.link);
 328
 329                 engine = (void *)rcu_access_pointer(node->base.request);
 330                 RCU_INIT_POINTER(node->base.request, ERR_PTR(-EAGAIN));
 331
 332                 parent = NULL;
 333                 p = &ref->tree.rb_node;
 334                 while (*p) {
 335                         parent = *p;
 336                         if (rb_entry(parent,
 337                                      struct active_node,
 338                                      node)->timeline < node->timeline)
 339                                 p = &parent->rb_right;
 340                         else
 341                                 p = &parent->rb_left;
 342                 }
 343                 rb_link_node(&node->node, parent, p);
 344                 rb_insert_color(&node->node, &ref->tree);
 345
 346                 llist_add((struct llist_node *)&node->base.link,
 347                           &engine->barrier_tasks);
 348                 intel_engine_pm_put(engine);
 349         }
 350         i915_active_release(ref);
 351 }
 352
 353 void i915_request_add_barriers(struct i915_request *rq)
 354 {
 355         struct intel_engine_cs *engine = rq->engine;
 356         struct llist_node *node, *next;
 357
 358         llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks))
 359                 list_add_tail((struct list_head *)node, &rq->active_list);
 360 }
 361
 362 int i915_active_request_set(struct i915_active_request *active,
 363                             struct i915_request *rq)
 364 {
 365         int err;
 366
 367         /* Must maintain ordering wrt previous active requests */
 368         err = i915_request_await_active_request(rq, active);
 369         if (err)
 370                 return err;
 371
 372         __i915_active_request_set(active, rq);
 373         return 0;
 374 }
 375
 376 void i915_active_retire_noop(struct i915_active_request *active,
 377                              struct i915_request *request)
 378 {
 379         /* Space left intentionally blank */
 380 }
 381
 382 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 383 #include "selftests/i915_active.c"
 384 #endif
 385
 386 static void i915_global_active_shrink(void)
 387 {
 388         kmem_cache_shrink(global.slab_cache);
 389 }
 390
 391 static void i915_global_active_exit(void)
 392 {
 393         kmem_cache_destroy(global.slab_cache);
 394 }
 395
 396 static struct i915_global_active global = { {
 397         .shrink = i915_global_active_shrink,
 398         .exit = i915_global_active_exit,
 399 } };
 400
 401 int __init i915_global_active_init(void)
 402 {
 403         global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
 404         if (!global.slab_cache)
 405                 return -ENOMEM;
 406
 407         i915_global_register(&global.base);
 408         return 0;
 409 }