cnat: remove rwlock on ts

Type: improvement

Remove rwlock contention on timestamps. ~10% pps with
10k sessions. Use fixed-size-pools of increasing sizes
starting with 4K, and with a x2 step each time.
We don't free/shrink allocated pools.

Change-Id: I5fea51faba40430106c823275a6356e81709d118
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>

src/plugins/cnat/cnat_types.h

@@ -148,9 +148,6 @@ typedef struct cnat_main_
   /* delay in seconds between two scans of session/clients tables */
   f64 scanner_timeout;
 
-  /* Lock for the timestamp pool */
-  clib_rwlock_t ts_lock;
-
   /* Index of the scanner process node */
   uword scanner_node_index;
 
@@ -175,6 +172,23 @@ typedef struct cnat_timestamp_t_
   u16 refcnt;
 } cnat_timestamp_t;
 
+/* Create the first pool with 1 << CNAT_TS_BASE_SIZE elts */
+#define CNAT_TS_BASE_SIZE (8)
+/* reserve the top CNAT_TS_MPOOL_BITS bits for finding the pool */
+#define CNAT_TS_MPOOL_BITS (6)
+
+typedef struct cnat_timestamp_mpool_t_
+{
+  /* Increasing fixed size pools of timestamps */
+  cnat_timestamp_t *ts_pools[1 << CNAT_TS_MPOOL_BITS];
+  /* Bitmap of pools with free space */
+  uword *ts_free;
+  /* Index of next pool to init */
+  u8 next_empty_pool_idx;
+  /* ts creation lock */
+  clib_spinlock_t ts_lock;
+} cnat_timestamp_mpool_t;
+
 typedef struct cnat_node_ctx_
 {
   f64 now;
@@ -188,8 +202,7 @@ extern u8 *format_cnat_endpoint (u8 * s, va_list * args);
 extern uword unformat_cnat_ep_tuple (unformat_input_t * input,
 				     va_list * args);
 extern uword unformat_cnat_ep (unformat_input_t * input, va_list * args);
-extern cnat_timestamp_t *cnat_timestamps;
-extern fib_source_t cnat_fib_source;
+extern cnat_timestamp_mpool_t cnat_timestamps;
 extern cnat_main_t cnat_main;
 
 extern char *cnat_error_strings[];