1 /*
2 * Copyright 2021 Google LLC
3 * SPDX-License-Identifier: MIT
4 */
5
6 #include "vn_renderer_internal.h"
7
8 /* 3 seconds */
9 #define VN_RENDERER_SHMEM_CACHE_EXPIRACY (3ll * 1000 * 1000)
10
11 void
vn_renderer_shmem_cache_init(struct vn_renderer_shmem_cache * cache,struct vn_renderer * renderer,vn_renderer_shmem_cache_destroy_func destroy_func)12 vn_renderer_shmem_cache_init(struct vn_renderer_shmem_cache *cache,
13 struct vn_renderer *renderer,
14 vn_renderer_shmem_cache_destroy_func destroy_func)
15 {
16 /* cache->bucket_mask is 32-bit and u_bit_scan is used */
17 static_assert(ARRAY_SIZE(cache->buckets) <= 32, "");
18
19 cache->renderer = renderer;
20 cache->destroy_func = destroy_func;
21
22 simple_mtx_init(&cache->mutex, mtx_plain);
23
24 for (uint32_t i = 0; i < ARRAY_SIZE(cache->buckets); i++) {
25 struct vn_renderer_shmem_bucket *bucket = &cache->buckets[i];
26 list_inithead(&bucket->shmems);
27 }
28
29 cache->initialized = true;
30 }
31
32 void
vn_renderer_shmem_cache_fini(struct vn_renderer_shmem_cache * cache)33 vn_renderer_shmem_cache_fini(struct vn_renderer_shmem_cache *cache)
34 {
35 if (!cache->initialized)
36 return;
37
38 while (cache->bucket_mask) {
39 const int idx = u_bit_scan(&cache->bucket_mask);
40 struct vn_renderer_shmem_bucket *bucket = &cache->buckets[idx];
41
42 list_for_each_entry_safe(struct vn_renderer_shmem, shmem,
43 &bucket->shmems, cache_head)
44 cache->destroy_func(cache->renderer, shmem);
45 }
46
47 simple_mtx_destroy(&cache->mutex);
48 }
49
50 static struct vn_renderer_shmem_bucket *
choose_bucket(struct vn_renderer_shmem_cache * cache,size_t size,int * out_idx)51 choose_bucket(struct vn_renderer_shmem_cache *cache,
52 size_t size,
53 int *out_idx)
54 {
55 assert(size);
56 if (unlikely(!util_is_power_of_two_or_zero64(size)))
57 return NULL;
58
59 const uint32_t idx = ffsll(size) - 1;
60 if (unlikely(idx >= ARRAY_SIZE(cache->buckets)))
61 return NULL;
62
63 *out_idx = idx;
64 return &cache->buckets[idx];
65 }
66
67 static void
vn_renderer_shmem_cache_remove_expired_locked(struct vn_renderer_shmem_cache * cache,int64_t now)68 vn_renderer_shmem_cache_remove_expired_locked(
69 struct vn_renderer_shmem_cache *cache, int64_t now)
70 {
71 uint32_t bucket_mask = cache->bucket_mask;
72 while (bucket_mask) {
73 const int idx = u_bit_scan(&bucket_mask);
74 struct vn_renderer_shmem_bucket *bucket = &cache->buckets[idx];
75
76 assert(!list_is_empty(&bucket->shmems));
77 const struct vn_renderer_shmem *last_shmem = list_last_entry(
78 &bucket->shmems, struct vn_renderer_shmem, cache_head);
79
80 /* remove expired shmems but keep at least the last one */
81 list_for_each_entry_safe(struct vn_renderer_shmem, shmem,
82 &bucket->shmems, cache_head) {
83 if (shmem == last_shmem ||
84 now - shmem->cache_timestamp < VN_RENDERER_SHMEM_CACHE_EXPIRACY)
85 break;
86
87 list_del(&shmem->cache_head);
88 cache->destroy_func(cache->renderer, shmem);
89 }
90 }
91 }
92
93 bool
vn_renderer_shmem_cache_add(struct vn_renderer_shmem_cache * cache,struct vn_renderer_shmem * shmem)94 vn_renderer_shmem_cache_add(struct vn_renderer_shmem_cache *cache,
95 struct vn_renderer_shmem *shmem)
96 {
97 assert(!vn_refcount_is_valid(&shmem->refcount));
98
99 int idx;
100 struct vn_renderer_shmem_bucket *bucket =
101 choose_bucket(cache, shmem->mmap_size, &idx);
102 if (!bucket)
103 return false;
104
105 const int64_t now = os_time_get();
106 shmem->cache_timestamp = now;
107
108 simple_mtx_lock(&cache->mutex);
109
110 vn_renderer_shmem_cache_remove_expired_locked(cache, now);
111
112 list_addtail(&shmem->cache_head, &bucket->shmems);
113 cache->bucket_mask |= 1 << idx;
114
115 simple_mtx_unlock(&cache->mutex);
116
117 return true;
118 }
119
120 struct vn_renderer_shmem *
vn_renderer_shmem_cache_get(struct vn_renderer_shmem_cache * cache,size_t size)121 vn_renderer_shmem_cache_get(struct vn_renderer_shmem_cache *cache,
122 size_t size)
123 {
124 int idx;
125 struct vn_renderer_shmem_bucket *bucket = choose_bucket(cache, size, &idx);
126 if (!bucket) {
127 VN_TRACE_SCOPE("shmem cache skip");
128 simple_mtx_lock(&cache->mutex);
129 cache->debug.cache_skip_count++;
130 simple_mtx_unlock(&cache->mutex);
131 return NULL;
132 }
133
134 struct vn_renderer_shmem *shmem = NULL;
135
136 simple_mtx_lock(&cache->mutex);
137 if (cache->bucket_mask & (1 << idx)) {
138 assert(!list_is_empty(&bucket->shmems));
139 shmem = list_first_entry(&bucket->shmems, struct vn_renderer_shmem,
140 cache_head);
141 list_del(&shmem->cache_head);
142
143 if (list_is_empty(&bucket->shmems))
144 cache->bucket_mask &= ~(1 << idx);
145
146 cache->debug.cache_hit_count++;
147 } else {
148 VN_TRACE_SCOPE("shmem cache miss");
149 cache->debug.cache_miss_count++;
150 }
151 simple_mtx_unlock(&cache->mutex);
152
153 return shmem;
154 }
155
156 /* for debugging only */
157 void
vn_renderer_shmem_cache_debug_dump(struct vn_renderer_shmem_cache * cache)158 vn_renderer_shmem_cache_debug_dump(struct vn_renderer_shmem_cache *cache)
159 {
160 simple_mtx_lock(&cache->mutex);
161
162 vn_log(NULL, "dumping shmem cache");
163 vn_log(NULL, " cache skip: %d", cache->debug.cache_skip_count);
164 vn_log(NULL, " cache hit: %d", cache->debug.cache_hit_count);
165 vn_log(NULL, " cache miss: %d", cache->debug.cache_miss_count);
166
167 uint32_t bucket_mask = cache->bucket_mask;
168 while (bucket_mask) {
169 const int idx = u_bit_scan(&bucket_mask);
170 const struct vn_renderer_shmem_bucket *bucket = &cache->buckets[idx];
171 uint32_t count = 0;
172 list_for_each_entry(struct vn_renderer_shmem, shmem, &bucket->shmems,
173 cache_head)
174 count++;
175 if (count)
176 vn_log(NULL, " buckets[%d]: %d shmems", idx, count);
177 }
178
179 simple_mtx_unlock(&cache->mutex);
180 }
181