Streamline code during finds to reduce contention on c_mutex.

Move Debug messages outside of c_mutex.  Other LDBM cache codes
also should be streamlined.  Resultant approaches should then
be applied to back-bdb2.

diff --git a/servers/slapd/back-ldbm/cache.c b/servers/slapd/back-ldbm/cache.c
index bbb9dd15ebfa8fa2376c78a46e40220f69e43e1f..d1a9dbad6234c386a5d9d5cbbe1e0a421f26b175 100644 (file)
--- a/servers/slapd/back-ldbm/cache.c
+++ b/servers/slapd/back-ldbm/cache.c
@@ -429,6 +429,7 @@ cache_find_entry_dn2id(
 {
        Entry           e, *ep;
        ID                      id;
+       int count = 0;
 
        e.e_dn = dn;
        e.e_ndn = dn_normalize_case( ch_strdup( dn ) );
@@ -440,51 +441,60 @@ try_again:
        if ( (ep = (Entry *) avl_find( cache->c_dntree, (caddr_t) &e,
                (AVL_CMP) entry_dn_cmp )) != NULL )
        {
+               id = ep->e_id;
+               count++;
+
                /*
                 * ep now points to an unlocked entry
                 * we do not need to lock the entry if we only
                 * check the state, refcnt, LRU, and id.
                 */
 
-#ifdef LDAP_DEBUG
                assert( ep->e_private );
-#endif
+
                /*
                 * entry is deleted or not fully created yet
                 */
                if ( LEI(ep)->lei_state != CACHE_ENTRY_READY ) {
-#ifdef LDAP_DEBUG
-                       assert(LEI(ep)->lei_state != CACHE_ENTRY_UNDEFINED);
-#endif
-                       Debug(LDAP_DEBUG_TRACE,
-                               "====> cache_find_entry_dn2id(\"%s\"): %ld (not ready) %d\n",
-                               dn, ep->e_id, LEI(ep)->lei_state);
+                       int state = LEI(ep)->lei_state;
+
+                       assert(state != CACHE_ENTRY_UNDEFINED);
 
                        /* free cache mutex */
                        ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
+
+                       Debug(LDAP_DEBUG_TRACE,
+                               "====> cache_find_entry_dn2id(\"%s\"): %ld (not ready) %d\n",
+                               dn, id, state);
+
                        ldap_pvt_thread_yield();
+
                        goto try_again;
                }
 
-               Debug(LDAP_DEBUG_TRACE,
-                       "====> cache_find_entry_dn2id(\"%s\"): %ld\n",
-                       dn, ep->e_id, 0);
-
                /* lru */
                LRU_DELETE( cache, ep );
                LRU_ADD( cache, ep );
                 
                /* save id */
                id = ep->e_id;
+
+               /* free cache mutex */
+               ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
+
+               Debug(LDAP_DEBUG_TRACE,
+                       "====> cache_find_entry_dn2id(\"%s\"): %ld (%d tries)\n",
+                       dn, id, count);
+
        } else {
+               /* free cache mutex */
+               ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
+
                id = NOID;
        }
 
        free(e.e_ndn);
 
-       /* free cache mutex */
-       ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
-
        return( id );
 }
 
@@ -501,6 +511,7 @@ cache_find_entry_id(
 {
        Entry   e;
        Entry   *ep;
+       int     count = 0;
 
        e.e_id = id;
 
@@ -511,30 +522,33 @@ try_again:
        if ( (ep = (Entry *) avl_find( cache->c_idtree, (caddr_t) &e,
                (AVL_CMP) entry_id_cmp )) != NULL )
        {
+               int state = LEI(ep)->lei_state;
+               count++;
+
 #ifdef LDAP_DEBUG
                assert( ep->e_private );
 #endif
                /*
                 * entry is deleted or not fully created yet
                 */
-               if ( LEI(ep)->lei_state != CACHE_ENTRY_READY ) {
+               if ( state != CACHE_ENTRY_READY ) {
+                       ID      ep_id = ep->e_id; 
+
 #ifdef LDAP_DEBUG
-                       assert(LEI(ep)->lei_state != CACHE_ENTRY_UNDEFINED);
+                       assert(state != CACHE_ENTRY_UNDEFINED);
 #endif
-                       Debug(LDAP_DEBUG_TRACE,
-                               "====> cache_find_entry_id( %ld ): %ld (not ready) %d\n",
-                               id, ep->e_id, LEI(ep)->lei_state);
 
                        /* free cache mutex */
                        ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
+
+                       Debug(LDAP_DEBUG_TRACE,
+                               "====> cache_find_entry_id( %ld ): %ld (not ready) %d\n",
+                               id, ep_id, state);
+
                        ldap_pvt_thread_yield();
                        goto try_again;
                }
 
-               Debug(LDAP_DEBUG_TRACE,
-                       "====> cache_find_entry_id( %ld, %s ) \"%s\" (found)\n",
-                       id, rw ? "w" : "r", ep->e_dn);
-
                /* acquire reader lock */
                if ( cache_entry_rdwr_trylock(ep, rw) == LDAP_PVT_THREAD_EBUSY ) {
                        /* could not acquire entry lock...
@@ -557,6 +571,10 @@ try_again:
                /* free cache mutex */
                ldap_pvt_thread_mutex_unlock( &cache->c_mutex );
 
+               Debug(LDAP_DEBUG_TRACE,
+                       "====> cache_find_entry_id( %ld ) \"%s\" (found) (%d tries)\n",
+                       id, ep->e_dn, count);
+
                return( ep );
        }