The lib internal cache improves throughput in high load
scenarios but for applications with a low request rate,
the cache size must be adapted to this situation.
Therefore the cache size should be changed to the current
requirements of the application during runtime.
---
libuuid/src/gen_uuid.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/libuuid/src/gen_uuid.c b/libuuid/src/gen_uuid.c
index e1ba3c3d0..619ef0131 100644
--- a/libuuid/src/gen_uuid.c
+++ b/libuuid/src/gen_uuid.c
@@ -528,25 +528,35 @@ int __uuid_generate_time_cont(uuid_t out, int *num, uint32_t cont_offset)
*/
static int uuid_generate_time_generic(uuid_t out) {
#ifdef HAVE_TLS
+ /* thread local cache for uuidd based requests */
+ const int cs_min = (1<<6);
+ const int cs_max = (1<<18);
+ const int cs_factor = 2;
THREAD_LOCAL int num = 0;
- THREAD_LOCAL int cache_size = 1;
+ THREAD_LOCAL int cache_size = cs_min;
+ THREAD_LOCAL int last_used = 0;
THREAD_LOCAL struct uuid uu;
THREAD_LOCAL time_t last_time = 0;
time_t now;
- if (num > 0) {
+ if (num > 0) { /* expire cache */
now = time(NULL);
- if (now > last_time+1)
+ if (now > last_time+1) {
+ last_used = cache_size - num;
num = 0;
+ }
}
- if (num <= 0) {
+ if (num <= 0) { /* fill cache */
/*
* num + OP_BULK provides a local cache in each application.
* Start with a small cache size to cover short running applications
- * and increment the cache size over the runntime.
+ * and adjust the cache size over the runntime.
*/
- if (cache_size < 1000000)
- cache_size *= 10;
+ if ((last_used == cache_size) && (cache_size < cs_max))
+ cache_size *= cs_factor;
+ else if ((last_used < (cache_size / cs_factor)) && (cache_size > cs_min))
+ cache_size /= cs_factor;
+
num = cache_size;
if (get_uuid_via_daemon(UUIDD_OP_BULK_TIME_UUID,
@@ -556,9 +566,11 @@ static int uuid_generate_time_generic(uuid_t out) {
num--;
return 0;
}
+ /* request to daemon failed, reset cache */
num = 0;
+ cache_size = cs_min;
}
- if (num > 0) {
+ if (num > 0) { /* serve uuid from cache */
uu.time_low++;
if (uu.time_low == 0) {
uu.time_mid++;
@@ -567,6 +579,8 @@ static int uuid_generate_time_generic(uuid_t out) {
}
num--;
uuid_pack(&uu, out);
+ if (num == 0)
+ last_used = cache_size;
return 0;
}
#else
--
2.37.1
