Otherwise for apps that don't seed the regular rand() we will always
remove old cache entries from the same dirs.
V2: assume bits returned by rand are independent uniformly distributed
bits and grab our hex value without taking the modulus of the whole
value, this also fixes a bug where 'f' was always missing.
---
src/util/disk_cache.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
index f2d67c9..f8677e3 100644
--- a/src/util/disk_cache.c
+++ b/src/util/disk_cache.c
@@ -34,20 +34,21 @@
#include <sys/statvfs.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>
#include <errno.h>
#include <dirent.h>
#include "zlib.h"
#include "util/crc32.h"
+#include "util/rand_xor.h"
#include "util/u_atomic.h"
#include "util/u_queue.h"
#include "util/mesa-sha1.h"
#include "util/ralloc.h"
#include "main/errors.h"
#include "util/macros.h"
#include "disk_cache.h"
/* Number of bits to mask off from a cache key to get an index. */
@@ -59,20 +60,23 @@
/* The number of keys that can be stored in the index. */
#define CACHE_INDEX_MAX_KEYS (1 << CACHE_INDEX_KEY_BITS)
struct disk_cache {
/* The path to the cache directory. */
char *path;
/* Thread queue for compressing and writing cache entries to disk */
struct util_queue cache_queue;
+ /* Seed for rand, which is used to pick a random directory */
+ uint64_t seed_xorshift128plus[2];
+
/* A pointer to the mmapped index file within the cache directory. */
uint8_t *index_mmap;
size_t index_mmap_size;
/* Pointer to total size of all objects in cache (within index_mmap) */
uint64_t *size;
/* Pointer to stored keys, (within index_mmap). */
uint8_t *stored_keys;
@@ -354,20 +358,23 @@ disk_cache_create(const char *gpu_name, const char
*timestamp)
cache->max_size = max_size;
/* A limit of 32 jobs was choosen as observations of Deus Ex start-up times
* showed that we reached at most 11 jobs on an Intel i5-6400 CPU@2.70GHz
* (a fairly modest desktop CPU). 1 thread was chosen because we don't
* really care about getting things to disk quickly just that it's not
* blocking other tasks.
*/
util_queue_init(&cache->cache_queue, "disk_cache", 32, 1);
+ /* Seed our rand function */
+ s_rand_xorshift128plus(cache->seed_xorshift128plus, true);
+
ralloc_free(local);
return cache;
fail:
if (fd != -1)
close(fd);
if (cache)
ralloc_free(cache);
ralloc_free(local);
@@ -559,37 +566,32 @@ is_two_character_sub_directory(const char *path, const
struct stat *sb,
/* If dir only contains '.' and '..' it must be empty */
if (subdir_entries <= 2)
return false;
return true;
}
static void
evict_lru_item(struct disk_cache *cache)
{
- const char hex[] = "0123456789abcde";
char *dir_path;
- int a, b;
- size_t size;
/* With a reasonably-sized, full cache, (and with keys generated
* from a cryptographic hash), we can choose two random hex digits
* and reasonably expect the directory to exist with a file in it.
* Provides pseudo-LRU eviction to reduce checking all cache files.
*/
- a = rand() % 16;
- b = rand() % 16;
-
- if (asprintf(&dir_path, "%s/%c%c", cache->path, hex[a], hex[b]) < 0)
+ uint64_t rand64 = rand_xorshift128plus(cache->seed_xorshift128plus);
+ if (asprintf(&dir_path, "%s/%02" PRIx64 , cache->path, rand64 & 0xff) < 0)
return;
- size = unlink_lru_file_from_directory(dir_path);
+ size_t size = unlink_lru_file_from_directory(dir_path);
free(dir_path);
if (size) {
p_atomic_add(cache->size, - (uint64_t)size);
return;
}
/* In the case where the random choice of directory didn't find
* something, we choose the least recently accessed from the
--
2.9.3
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