1 /*
2 * Copyright (c) 2020 Collabora, Ltd.
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 FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 *
23 * Authors (Collabora):
24 * Alyssa Rosenzweig <[email protected]>
25 */
26
27 /* Index buffer min/max cache. We need to calculate the min/max for arbitrary
28 * slices (start, start + count) of the index buffer at drawtime. As this can
29 * be quite expensive, we cache. Conceptually, we just use a hash table mapping
30 * the key (start, count) to the value (min, max). In practice, mesa's hash
31 * table implementation is higher overhead than we would like and makes
32 * handling memory usage a little complicated. So we use this data structure
33 * instead. Searching is O(n) to the size, but the size is capped at the
34 * PANFROST_MINMAX_SIZE constant (so this is a tradeoff between cache hit/miss
35 * ratio and cache search speed). Note that keys are adjacent so we get cache
36 * line alignment benefits. Insertion is O(1) and in-order until the cache
37 * fills up, after that it evicts the oldest cached value in a ring facilitated
38 * by index.
39 */
40
41 #include "pan_minmax_cache.h"
42 #include "util/macros.h"
43
44 bool
panfrost_minmax_cache_get(struct panfrost_minmax_cache * cache,unsigned start,unsigned count,unsigned * min_index,unsigned * max_index)45 panfrost_minmax_cache_get(struct panfrost_minmax_cache *cache, unsigned start,
46 unsigned count, unsigned *min_index,
47 unsigned *max_index)
48 {
49 uint64_t ht_key = (((uint64_t)count) << 32) | start;
50 bool found = false;
51
52 if (!cache)
53 return false;
54
55 for (unsigned i = 0; i < cache->size; ++i) {
56 if (cache->keys[i] == ht_key) {
57 uint64_t hit = cache->values[i];
58
59 *min_index = hit & 0xffffffff;
60 *max_index = hit >> 32;
61 found = true;
62 break;
63 }
64 }
65
66 return found;
67 }
68
69 void
panfrost_minmax_cache_add(struct panfrost_minmax_cache * cache,unsigned start,unsigned count,unsigned min_index,unsigned max_index)70 panfrost_minmax_cache_add(struct panfrost_minmax_cache *cache, unsigned start,
71 unsigned count, unsigned min_index,
72 unsigned max_index)
73 {
74 uint64_t ht_key = (((uint64_t)count) << 32) | start;
75 uint64_t value = min_index | (((uint64_t)max_index) << 32);
76 unsigned index = 0;
77
78 if (!cache)
79 return;
80
81 if (cache->size == PANFROST_MINMAX_SIZE) {
82 index = cache->index++;
83 cache->index = cache->index % PANFROST_MINMAX_SIZE;
84 } else {
85 index = cache->size++;
86 }
87
88 cache->keys[index] = ht_key;
89 cache->values[index] = value;
90 }
91
92 /* If we've been caching min/max indices and we update the index
93 * buffer, that may invalidate the min/max. Check what's been cached vs
94 * what we've written, and throw out invalid entries. */
95
96 void
panfrost_minmax_cache_invalidate(struct panfrost_minmax_cache * cache,size_t offset,size_t size)97 panfrost_minmax_cache_invalidate(struct panfrost_minmax_cache *cache,
98 size_t offset, size_t size)
99 {
100 /* Ensure there is a cache to invalidate and a write */
101 if (!cache)
102 return;
103
104 unsigned valid_count = 0;
105
106 for (unsigned i = 0; i < cache->size; ++i) {
107 uint64_t key = cache->keys[i];
108
109 uint32_t start = key & 0xffffffff;
110 uint32_t count = key >> 32;
111
112 /* 1D range intersection */
113 bool invalid = MAX2(offset, start) <
114 MIN2(offset + size, start + count);
115 if (!invalid) {
116 cache->keys[valid_count] = key;
117 cache->values[valid_count] = cache->values[i];
118 valid_count++;
119 }
120 }
121
122 cache->size = valid_count;
123 cache->index = 0;
124 }
125