Use system property to set dns cache size
Use system property ro.net.dns_cache_size to set
the size of the cache. If the system property
is not set the default cache size is defined by
CONFIG_MAX_ENTRIES.
The number of entries in the hash table will be equal
to the number of max entries allowed in the cache.
Change-Id: I77d69d7c178937fa483d0b40512483ad29232d28
diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c
index f0c51ab..e6302ed 100644
--- a/libc/netbsd/resolv/res_cache.c
+++ b/libc/netbsd/resolv/res_cache.c
@@ -34,6 +34,7 @@
#include <errno.h>
#include "arpa_nameser.h"
+#include <sys/system_properties.h>
/* This code implements a small and *simple* DNS resolver cache.
*
@@ -106,7 +107,7 @@
*/
#define CONFIG_SECONDS (60*10) /* 10 minutes */
-/* maximum number of entries kept in the cache. This value has been
+/* default number of entries kept in the cache. This value has been
* determined by browsing through various sites and counting the number
* of corresponding requests. Keep in mind that our framework is currently
* performing two requests per name lookup (one for IPv4, the other for IPv6)
@@ -125,10 +126,16 @@
* most high-level websites use lots of media/ad servers with different names
* but these are generally reused when browsing through the site.
*
- * As such, a valud of 64 should be relatively conformtable at the moment.
+ * As such, a value of 64 should be relatively comfortable at the moment.
+ *
+ * The system property ro.net.dns_cache_size can be used to override the default
+ * value with a custom value
*/
#define CONFIG_MAX_ENTRIES 64
+/* name of the system property that can be used to set the cache size */
+#define DNS_CACHE_SIZE_PROP_NAME "ro.net.dns_cache_size"
+
/****************************************************************************/
/****************************************************************************/
/***** *****/
@@ -1147,15 +1154,15 @@
* for simplicity, the hash-table fields 'hash' and 'hlink' are
* inlined in the Entry structure.
*/
-#define MAX_HASH_ENTRIES (2*CONFIG_MAX_ENTRIES)
typedef struct resolv_cache {
+ int max_entries;
int num_entries;
Entry mru_list;
pthread_mutex_t lock;
unsigned generation;
int last_id;
- Entry* entries[ MAX_HASH_ENTRIES ];
+ Entry* entries;
} Cache;
@@ -1167,9 +1174,9 @@
int nn;
time_t now = _time_now();
- for (nn = 0; nn < MAX_HASH_ENTRIES; nn++)
+ for (nn = 0; nn < cache->max_entries; nn++)
{
- Entry** pnode = &cache->entries[nn];
+ Entry** pnode = (Entry**) &cache->entries[nn];
while (*pnode != NULL) {
Entry* node = *pnode;
@@ -1187,6 +1194,30 @@
"*************************");
}
+/* Return max number of entries allowed in the cache,
+ * i.e. cache size. The cache size is either defined
+ * by system property ro.net.dns_cache_size or by
+ * CONFIG_MAX_ENTRIES if system property not set
+ * or set to invalid value. */
+static int
+_res_cache_get_max_entries( void )
+{
+ int result = -1;
+ char cache_size[PROP_VALUE_MAX];
+
+ if (__system_property_get(DNS_CACHE_SIZE_PROP_NAME, cache_size) > 0) {
+ result = atoi(cache_size);
+ }
+
+ // ro.net.dns_cache_size not set or set to negative value
+ if (result <= 0) {
+ result = CONFIG_MAX_ENTRIES;
+ }
+
+ XLOG("cache size: %d", result);
+ return result;
+}
+
static struct resolv_cache*
_resolv_cache_create( void )
{
@@ -1194,10 +1225,17 @@
cache = calloc(sizeof(*cache), 1);
if (cache) {
- cache->generation = ~0U;
- pthread_mutex_init( &cache->lock, NULL );
- cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list;
- XLOG("%s: cache created\n", __FUNCTION__);
+ cache->max_entries = _res_cache_get_max_entries();
+ cache->entries = calloc(sizeof(*cache->entries), cache->max_entries);
+ if (cache->entries) {
+ cache->generation = ~0U;
+ pthread_mutex_init( &cache->lock, NULL );
+ cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list;
+ XLOG("%s: cache created\n", __FUNCTION__);
+ } else {
+ free(cache);
+ cache = NULL;
+ }
}
return cache;
}
@@ -1288,8 +1326,8 @@
_cache_lookup_p( Cache* cache,
Entry* key )
{
- int index = key->hash % MAX_HASH_ENTRIES;
- Entry** pnode = &cache->entries[ key->hash % MAX_HASH_ENTRIES ];
+ int index = key->hash % cache->max_entries;
+ Entry** pnode = (Entry**) &cache->entries[ index ];
while (*pnode != NULL) {
Entry* node = *pnode;
@@ -1470,7 +1508,7 @@
goto Exit;
}
- if (cache->num_entries >= CONFIG_MAX_ENTRIES) {
+ if (cache->num_entries >= cache->max_entries) {
_cache_remove_oldest(cache);
/* need to lookup again */
lookup = _cache_lookup_p(cache, key);