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lru cache now works as intended

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This commit is contained in:
Alessandro Mauri 2023-03-12 13:43:30 +01:00
parent 8c1f4f5ee2
commit 5455449bf9
5 changed files with 54 additions and 29 deletions
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55
text_rendering/generic_cache.h
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@ -5,26 +5,26 @@
#include "generic_hash.h"
#define CACHE_SIZE 512
#define CACHE_NCYCLES (CACHE_SIZE/2)
#define CACHE_NCYCLES (CACHE_SIZE*2/3)
#define CACHE_BSIZE (((CACHE_SIZE+0x3f)&(~0x3f))>>6)
#define CACHE_BRESET(b) for (int i = 0; i < CACHE_BSIZE; b[i++] = 0);
#define CACHE_BSET(b, x) b[(x)>>6] |= (uint64_t)1<<((x)%64)
#define CACHE_BTEST(b, x) (b[(x)>>6]&((uint64_t)1<<((x)%64)))
#define CACHE_BSET(b, x) b[(x)>>6] |= (uint64_t)1<<((x)&63)
#define CACHE_BTEST(b, x) (b[(x)>>6]&((uint64_t)1<<((x)&63)))
// FIXME: this cache implementation is not really generic since it expects an unsigned
// as the code and not a generic type
// FIXME: when resetting the bitmap all references to overwritten elements are
// invalidated, this really means that
// 1) we get data mismatches
// 2) this is not a good LRU cache
#define CACHE_SET(c, x) \
#define CACHE_USED(c, x) \
{ \
if (++(c->cycles) > CACHE_NCYCLES) { \
CACHE_BRESET(c->bitmap); \
c->cycles=0;} \
CACHE_BSET(c->bitmap, x); \
for (int i = 0; i < CACHE_BSIZE; i++) { \
c->present[i] &= c->used[i]; \
c->used[i] = 0; \
} \
c->cycles = 0; \
} \
CACHE_BSET(c->used, x); \
}
@ -33,18 +33,21 @@ HASH_DECL(name##table, uint32_t, uint32_t, hashfn, cmpfn) \
struct name { \
struct name##table_ref *table; \
type *array; \
uint64_t *bitmap; \
uint64_t *present, *used; \
int cycles; \
}; \
\
\
/* FIXME: check for allocation errors */ \
struct name name##_init(void) \
{ \
struct name##table_ref *t = name##table_create(CACHE_SIZE); \
type *a = malloc(sizeof(type)*CACHE_SIZE); \
uint64_t *b = malloc(sizeof(uint64_t)*CACHE_BSIZE); \
CACHE_BRESET(b); \
return (struct name){ .table = t, .array = a, .bitmap = b, 0}; \
uint64_t *p = malloc(sizeof(uint64_t)*CACHE_BSIZE); \
uint64_t *u = malloc(sizeof(uint64_t)*CACHE_BSIZE); \
CACHE_BRESET(p); \
CACHE_BRESET(u); \
return (struct name){.table=t, .array=a, .present=p, .used=u, 0}; \
} \
\
\
@ -53,7 +56,8 @@ void name##_free(struct name *cache) \
if (cache) { \
name##table_destroy(cache->table); \
free(cache->array); \
free(cache->bitmap); \
free(cache->present); \
free(cache->used); \
} \
} \
\
@ -66,21 +70,25 @@ const type * name##_search(struct name *cache, uint32_t code) \
/* MISS */ \
if (!r || !cmpfn(code, r->code)) \
return NULL; \
/* MISS, the data is not valid (not present) */ \
if (!CACHE_BTEST(cache->present, r->data)) \
return NULL; \
/* HIT, set as recently used */ \
CACHE_SET(cache, r->data); \
CACHE_USED(cache, r->data); \
return (&cache->array[r->data]); \
} \
\
\
/* Look for a free spot in the present bitmap and return its index */ \
int name##_get(struct name *cache) \
{ \
if (!cache) return -1; \
int x = 0; \
for (int b = 0; b < CACHE_BSIZE; b++) { \
if (cache->bitmap[b] == 0) x = 64; \
else x = __builtin_clzll(cache->bitmap[b]); \
if (cache->present[b] == 0) x = 64; \
else x = __builtin_clzll(cache->present[b]); \
x = 64-x; \
if (!CACHE_BTEST(cache->bitmap, x+64*b)) \
if (!CACHE_BTEST(cache->present, x+64*b)) \
return x+64*b; \
} \
return 0; \
@ -93,9 +101,12 @@ const type * name##_insert(struct name *cache, const type *g, uint32_t code, int
type *spot = NULL; \
/* x is the index to the cache array, it has to come from the user */ \
/* check if the spot is free */ \
if (x < 0 || CACHE_BTEST(cache->bitmap, x)) \
if (x < 0 || CACHE_BTEST(cache->present, x)) \
return NULL; \
CACHE_SET(cache, x) \
/* Set used and present */ \
CACHE_USED(cache, x) \
CACHE_BSET(cache->present, x); \
CACHE_BSET(cache->used, x); \
spot = &(cache->array[x]); \
*spot = *g; \
struct name##table_entry e = { .code = code, .data = x}; \