]> git.sur5r.net Git - openldap/blobdiff - servers/slapd/back-bdb/cache.c
Bypass a few redundant locks
[openldap] / servers / slapd / back-bdb / cache.c
index 4bff759a9e14febe0c78280a9b83661b7343feb9..5c9dc31490405d4a4e79bcadc1cc97e1e9213e57 100644 (file)
@@ -29,9 +29,9 @@
 #include "ldap_rq.h"
 
 #ifdef BDB_HIER
-#define bdb_cache_lru_add      hdb_cache_lru_add
+#define bdb_cache_lru_purge    hdb_cache_lru_purge
 #endif
-static void bdb_cache_lru_add( struct bdb_info *bdb, EntryInfo *ei );
+static void bdb_cache_lru_purge( struct bdb_info *bdb );
 
 static int     bdb_cache_delete_internal(Cache *cache, EntryInfo *e, int decr);
 #ifdef LDAP_DEBUG
@@ -40,41 +40,94 @@ static void bdb_lru_print(Cache *cache);
 #endif
 #endif
 
+/* For concurrency experiments only! */
+#if 0
+#define        ldap_pvt_thread_rdwr_wlock(a)   0
+#define        ldap_pvt_thread_rdwr_wunlock(a) 0
+#define        ldap_pvt_thread_rdwr_rlock(a)   0
+#define        ldap_pvt_thread_rdwr_runlock(a) 0
+#endif
+
+#if 0
+#define ldap_pvt_thread_mutex_trylock(a) 0
+#endif
+
 static EntryInfo *
 bdb_cache_entryinfo_new( Cache *cache )
 {
        EntryInfo *ei = NULL;
 
        if ( cache->c_eifree ) {
-               ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
+               ldap_pvt_thread_mutex_lock( &cache->c_eifree_mutex );
                if ( cache->c_eifree ) {
                        ei = cache->c_eifree;
                        cache->c_eifree = ei->bei_lrunext;
                }
-               ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+               ldap_pvt_thread_mutex_unlock( &cache->c_eifree_mutex );
        }
-       if ( ei ) {
-               ei->bei_lrunext = NULL;
-               ei->bei_state = 0;
-       } else {
-               ei = ch_calloc(1, sizeof(struct bdb_entry_info));
+       if ( !ei ) {
+               ei = ch_calloc(1, sizeof(EntryInfo));
                ldap_pvt_thread_mutex_init( &ei->bei_kids_mutex );
        }
 
+       ei->bei_state = CACHE_ENTRY_REFERENCED;
+
        return ei;
 }
 
+/* Note - we now use a Second-Chance / Clock algorithm instead of
+ * Least-Recently-Used. This tremendously improves concurrency
+ * because we no longer need to manipulate the lists every time an
+ * entry is touched. We only need to lock the lists when adding
+ * or deleting an entry. It's now a circular doubly-linked list.
+ * We always append to the tail, but the head traverses the circle
+ * during a purge operation.
+ */
+static void
+bdb_cache_lru_link( Cache *cache, EntryInfo *ei )
+{
+       /* Insert into circular LRU list */
+       ldap_pvt_thread_mutex_lock( &cache->lru_tail_mutex );
+       ei->bei_lruprev = cache->c_lrutail;
+       if ( cache->c_lrutail ) {
+               ei->bei_lrunext = cache->c_lrutail->bei_lrunext;
+               cache->c_lrutail->bei_lrunext = ei;
+               if ( ei->bei_lrunext )
+                       ei->bei_lrunext->bei_lruprev = ei;
+       } else {
+               ei->bei_lrunext = ei->bei_lruprev = ei;
+               cache->c_lruhead = ei;
+       }
+       cache->c_lrutail = ei;
+       ldap_pvt_thread_mutex_unlock( &cache->lru_tail_mutex );
+}
+
+#ifdef NO_THREADS
+#define NO_DB_LOCK
+#endif
+
+/* #define NO_DB_LOCK 1 */
+/* Note: The BerkeleyDB locks are much slower than regular
+ * mutexes or rdwr locks. But the BDB implementation has the
+ * advantage of using a fixed size lock table, instead of
+ * allocating a lock object per entry in the DB. That's a
+ * key benefit for scaling. It also frees us from worrying
+ * about undetectable deadlocks between BDB activity and our
+ * own cache activity. It's still worth exploring faster
+ * alternatives though.
+ */
+
 /* Atomically release and reacquire a lock */
 int
 bdb_cache_entry_db_relock(
-       DB_ENV *env,
+       struct bdb_info *bdb,
        u_int32_t locker,
        EntryInfo *ei,
        int rw,
        int tryOnly,
        DB_LOCK *lock )
 {
-#ifdef NO_THREADS
+#ifdef NO_DB_LOCK
        return 0;
 #else
        int     rc;
@@ -92,7 +145,7 @@ bdb_cache_entry_db_relock(
        list[1].lock = *lock;
        list[1].mode = rw ? DB_LOCK_WRITE : DB_LOCK_READ;
        list[1].obj = &lockobj;
-       rc = env->lock_vec(env, locker, tryOnly ? DB_LOCK_NOWAIT : 0,
+       rc = bdb->bi_dbenv->lock_vec(bdb->bi_dbenv, locker, tryOnly ? DB_LOCK_NOWAIT : 0,
                list, 2, NULL );
 
        if (rc && !tryOnly) {
@@ -107,10 +160,10 @@ bdb_cache_entry_db_relock(
 }
 
 static int
-bdb_cache_entry_db_lock( DB_ENV *env, u_int32_t locker, EntryInfo *ei,
+bdb_cache_entry_db_lock( struct bdb_info *bdb, u_int32_t locker, EntryInfo *ei,
        int rw, int tryOnly, DB_LOCK *lock )
 {
-#ifdef NO_THREADS
+#ifdef NO_DB_LOCK
        return 0;
 #else
        int       rc;
@@ -127,7 +180,7 @@ bdb_cache_entry_db_lock( DB_ENV *env, u_int32_t locker, EntryInfo *ei,
        lockobj.data = &ei->bei_id;
        lockobj.size = sizeof(ei->bei_id) + 1;
 
-       rc = LOCK_GET(env, locker, tryOnly ? DB_LOCK_NOWAIT : 0,
+       rc = LOCK_GET(bdb->bi_dbenv, locker, tryOnly ? DB_LOCK_NOWAIT : 0,
                                        &lockobj, db_rw, lock);
        if (rc && !tryOnly) {
                Debug( LDAP_DEBUG_TRACE,
@@ -135,20 +188,20 @@ bdb_cache_entry_db_lock( DB_ENV *env, u_int32_t locker, EntryInfo *ei,
                        ei->bei_id, rw, rc );
        }
        return rc;
-#endif /* NO_THREADS */
+#endif /* NO_DB_LOCK */
 }
 
 int
-bdb_cache_entry_db_unlock ( DB_ENV *env, DB_LOCK *lock )
+bdb_cache_entry_db_unlock ( struct bdb_info *bdb, DB_LOCK *lock )
 {
-#ifdef NO_THREADS
+#ifdef NO_DB_LOCK
        return 0;
 #else
        int rc;
 
-       if ( !lock ) return 0;
+       if ( !lock || lock->mode == DB_LOCK_NG ) return 0;
 
-       rc = LOCK_PUT ( env, lock );
+       rc = LOCK_PUT ( bdb->bi_dbenv, lock );
        return rc;
 #endif
 }
@@ -165,34 +218,6 @@ bdb_cache_entryinfo_destroy( EntryInfo *e )
        return 0;
 }
 
-#define LRU_DELETE( cache, ei ) do { \
-       if ( (ei)->bei_lruprev != NULL ) { \
-               (ei)->bei_lruprev->bei_lrunext = (ei)->bei_lrunext; \
-       } else { \
-               (cache)->c_lruhead = (ei)->bei_lrunext; \
-       } \
-       if ( (ei)->bei_lrunext != NULL ) { \
-               (ei)->bei_lrunext->bei_lruprev = (ei)->bei_lruprev; \
-       } else { \
-               (cache)->c_lrutail = (ei)->bei_lruprev; \
-       } \
-       (ei)->bei_lrunext = (ei)->bei_lruprev = NULL; \
-} while(0)
-
-#define LRU_ADD( cache, ei ) do { \
-       (ei)->bei_lrunext = (cache)->c_lruhead; \
-       if ( (ei)->bei_lrunext != NULL ) { \
-               (ei)->bei_lrunext->bei_lruprev = (ei); \
-       } \
-       (cache)->c_lruhead = (ei); \
-       (ei)->bei_lruprev = NULL; \
-       if ( !ldap_pvt_thread_mutex_trylock( &(cache)->lru_tail_mutex )) { \
-               if ( (cache)->c_lrutail == NULL ) \
-                       (cache)->c_lrutail = (ei); \
-               ldap_pvt_thread_mutex_unlock( &(cache)->lru_tail_mutex ); \
-       } \
-} while(0)
-
 /* Do a length-ordered sort on normalized RDNs */
 static int
 bdb_rdn_cmp( const void *v_e1, const void *v_e2 )
@@ -267,6 +292,7 @@ bdb_entryinfo_add_internal(
                ei->bei_parent->bei_ckids++;
 #endif
        }
+       bdb_cache_lru_link( &bdb->bi_cache, ei2 );
 
        *res = ei2;
        return 0;
@@ -315,6 +341,7 @@ bdb_cache_find_ndn(
        }
        
        for ( bdb_cache_entryinfo_lock( eip ); eip; ) {
+               eip->bei_state |= CACHE_ENTRY_REFERENCED;
                ei.bei_parent = eip;
                ei2 = (EntryInfo *)avl_find( eip->bei_kids, &ei, bdb_rdn_cmp );
                if ( !ei2 ) {
@@ -392,7 +419,6 @@ hdb_cache_find_parent(
        struct bdb_info *bdb = (struct bdb_info *) op->o_bd->be_private;
        EntryInfo ei, eip, *ei2 = NULL, *ein = NULL, *eir = NULL;
        int rc;
-       int addlru = 0;
 
        ei.bei_id = id;
        ei.bei_kids = NULL;
@@ -418,7 +444,7 @@ hdb_cache_find_parent(
                ei.bei_ckids = 0;
                
                /* This node is not fully connected yet */
-               ein->bei_state = CACHE_ENTRY_NOT_LINKED;
+               ein->bei_state |= CACHE_ENTRY_NOT_LINKED;
 
                /* Insert this node into the ID tree */
                ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
@@ -440,8 +466,8 @@ hdb_cache_find_parent(
                                ein->bei_ckids++;
                                bdb_cache_entryinfo_unlock( ein );
                        }
-                       addlru = 0;
-
+               } else {
+                       bdb_cache_lru_link( &bdb->bi_cache, ein );
                }
 
                /* If this is the first time, save this node
@@ -464,25 +490,22 @@ hdb_cache_find_parent(
                                bdb->bi_cache.c_leaves++;
                ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
 
-               if ( addlru ) {
-                       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_head_mutex );
-                       bdb_cache_lru_add( bdb, ein );
-               }
-               addlru = 1;
-
                /* Got the parent, link in and we're done. */
                if ( ei2 ) {
                        bdb_cache_entryinfo_lock( ei2 );
                        ein->bei_parent = ei2;
+
                        avl_insert( &ei2->bei_kids, (caddr_t)ein, bdb_rdn_cmp,
                                avl_dup_error);
                        ei2->bei_ckids++;
-                       bdb_cache_entryinfo_unlock( ei2 );
-                       bdb_cache_entryinfo_lock( eir );
 
                        /* Reset all the state info */
                        for (ein = eir; ein != ei2; ein=ein->bei_parent)
                                ein->bei_state &= ~CACHE_ENTRY_NOT_LINKED;
+
+                       bdb_cache_entryinfo_unlock( ei2 );
+                       bdb_cache_entryinfo_lock( eir );
+
                        *res = eir;
                        break;
                }
@@ -531,24 +554,21 @@ int hdb_cache_load(
 }
 #endif
 
-/* caller must have lru_head_mutex locked. mutex
- * will be unlocked on return.
- */
 static void
-bdb_cache_lru_add(
-       struct bdb_info *bdb,
-       EntryInfo *ei )
+bdb_cache_lru_purge( struct bdb_info *bdb )
 {
        DB_LOCK         lock, *lockp;
-       EntryInfo *elru, *elprev;
-       int count = 0;
+       EntryInfo *elru, *elnext;
+       int count, islocked;
 
-       LRU_ADD( &bdb->bi_cache, ei );
-       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
+       /* Don't bother if we can't get the lock */
+       if ( ldap_pvt_thread_mutex_trylock( &bdb->bi_cache.lru_head_mutex ) )
+               return;
 
-       /* See if we're above the cache size limit */
-       if ( bdb->bi_cache.c_cursize <= bdb->bi_cache.c_maxsize )
+       if ( bdb->bi_cache.c_cursize <= bdb->bi_cache.c_maxsize ) {
+               ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
                return;
+       }
 
        if ( bdb->bi_cache.c_locker ) {
                lockp = &lock;
@@ -556,28 +576,43 @@ bdb_cache_lru_add(
                lockp = NULL;
        }
 
-       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_tail_mutex );
-
+       count = 0;
        /* Look for an unused entry to remove */
-       for (elru = bdb->bi_cache.c_lrutail; elru; elru = elprev ) {
-               elprev = elru->bei_lruprev;
+       for (elru = bdb->bi_cache.c_lruhead; elru; elru = elnext ) {
+               elnext = elru->bei_lrunext;
+
+               if ( ldap_pvt_thread_mutex_trylock( &elru->bei_kids_mutex ))
+                       continue;
+
+               /* This flag implements the clock replacement behavior */
+               if ( elru->bei_state & ( CACHE_ENTRY_REFERENCED )) {
+                       elru->bei_state &= ~CACHE_ENTRY_REFERENCED;
+                       bdb_cache_entryinfo_unlock( elru );
+                       continue;
+               }
+
+               /* If this node is in the process of linking into the cache,
+                * or this node is being deleted, skip it.
+                *
+                * Also, if this node has no entry attached, skip it, there's
+                * nothing to purge anyway.
+                */
+               if (( elru->bei_state & ( CACHE_ENTRY_NOT_LINKED |
+                       CACHE_ENTRY_DELETED | CACHE_ENTRY_LOADING )) ||
+                       !elru->bei_e ) {
+                       bdb_cache_entryinfo_unlock( elru );
+                       continue;
+               }
+
+               /* entryinfo is locked */
+               islocked = 1;
 
                /* If we can successfully writelock it, then
                 * the object is idle.
                 */
-               if ( bdb_cache_entry_db_lock( bdb->bi_dbenv,
-                               bdb->bi_cache.c_locker, elru, 1, 1, lockp ) == 0 ) {
+               if ( bdb_cache_entry_db_lock( bdb,
+                       bdb->bi_cache.c_locker, elru, 1, 1, lockp ) == 0 ) {
 
-                       int stop = 0;
-
-                       /* If this node is in the process of linking into the cache,
-                        * or this node is being deleted, skip it.
-                        */
-                       if ( elru->bei_state &
-                               ( CACHE_ENTRY_NOT_LINKED | CACHE_ENTRY_DELETED )) {
-                               bdb_cache_entry_db_unlock( bdb->bi_dbenv, lockp );
-                               continue;
-                       }
                        /* Free entry for this node if it's present */
                        if ( elru->bei_e ) {
                                elru->bei_e->e_private = NULL;
@@ -589,6 +624,8 @@ bdb_cache_lru_add(
                                elru->bei_e = NULL;
                                count++;
                        }
+                       bdb_cache_entry_db_unlock( bdb, lockp );
+
                        /* ITS#4010 if we're in slapcat, and this node is a leaf
                         * node, free it.
                         *
@@ -598,30 +635,27 @@ bdb_cache_lru_add(
                         */
                        if ( slapMode & SLAP_TOOL_READONLY ) {
                                if ( !elru->bei_kids ) {
-                                       /* This does LRU_DELETE for us */
                                        bdb_cache_delete_internal( &bdb->bi_cache, elru, 0 );
                                        bdb_cache_delete_cleanup( &bdb->bi_cache, elru );
+                                       islocked = 0;
                                }
                                /* Leave node on LRU list for a future pass */
-                       } else {
-                               LRU_DELETE( &bdb->bi_cache, elru );
                        }
-                       bdb_cache_entry_db_unlock( bdb->bi_dbenv, lockp );
-
-                       if ( count == bdb->bi_cache.c_minfree ) {
-                               ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
-                               bdb->bi_cache.c_cursize -= bdb->bi_cache.c_minfree;
-                               if ( bdb->bi_cache.c_maxsize - bdb->bi_cache.c_cursize >=
-                                       bdb->bi_cache.c_minfree )
-                                       stop = 1;
-                               count = 0;
-                               ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
-                       }
-                       if (stop) break;
+               }
+
+               if ( islocked )
+                       bdb_cache_entryinfo_unlock( elru );
+
+               if ( count >= bdb->bi_cache.c_minfree ) {
+                       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
+                       bdb->bi_cache.c_cursize -= count;
+                       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );
+                       break;
                }
        }
 
-       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_tail_mutex );
+       bdb->bi_cache.c_lruhead = elnext;
+       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
 }
 
 EntryInfo *
@@ -710,6 +744,7 @@ again:      ldap_pvt_thread_rdwr_rlock( &bdb->bi_cache.c_rwlock );
                                &ep->e_nname, eip );
                        if ( *eip ) islocked = 1;
                        if ( rc ) {
+                               ep->e_private = NULL;
 #ifdef SLAP_ZONE_ALLOC
                                bdb_entry_return( bdb, ep, (*eip)->bei_zseq );
 #else
@@ -746,19 +781,13 @@ load1:
                                bdb_cache_entryinfo_unlock( *eip );
                                islocked = 0;
                        }
-                       rc = bdb_cache_entry_db_lock( bdb->bi_dbenv, locker, *eip, 0, 0, lock );
+                       rc = bdb_cache_entry_db_lock( bdb, locker, *eip, load, 0, lock );
                        if ( (*eip)->bei_state & CACHE_ENTRY_DELETED ) {
                                rc = DB_NOTFOUND;
-                               bdb_cache_entry_db_unlock( bdb->bi_dbenv, lock );
+                               bdb_cache_entry_db_unlock( bdb, lock );
                        } else if ( rc == 0 ) {
                                if ( load ) {
-                                       /* Give up original read lock, obtain write lock
-                                        */
-                                   if ( rc == 0 ) {
-                                               rc = bdb_cache_entry_db_relock( bdb->bi_dbenv, locker,
-                                                       *eip, 1, 0, lock );
-                                       }
-                                       if ( rc == 0 && !ep) {
+                                       if ( !ep) {
                                                rc = bdb_id2entry( op->o_bd, tid, locker, id, &ep );
                                        }
                                        if ( rc == 0 ) {
@@ -772,21 +801,22 @@ load1:
 #endif
                                                ep = NULL;
                                        }
+                                       bdb_cache_entryinfo_lock( *eip );
                                        (*eip)->bei_state ^= CACHE_ENTRY_LOADING;
+                                       bdb_cache_entryinfo_unlock( *eip );
                                        if ( rc == 0 ) {
                                                /* If we succeeded, downgrade back to a readlock. */
-                                               rc = bdb_cache_entry_db_relock( bdb->bi_dbenv, locker,
+                                               rc = bdb_cache_entry_db_relock( bdb, locker,
                                                        *eip, 0, 0, lock );
                                        } else {
                                                /* Otherwise, release the lock. */
-                                               bdb_cache_entry_db_unlock( bdb->bi_dbenv, lock );
+                                               bdb_cache_entry_db_unlock( bdb, lock );
                                        }
                                } else if ( !(*eip)->bei_e ) {
                                        /* Some other thread is trying to load the entry,
-                                        * give it a chance to finish.
+                                        * wait for it to finish.
                                         */
-                                       bdb_cache_entry_db_unlock( bdb->bi_dbenv, lock );
-                                       ldap_pvt_thread_yield();
+                                       bdb_cache_entry_db_unlock( bdb, lock );
                                        bdb_cache_entryinfo_lock( *eip );
                                        islocked = 1;
                                        goto load1;
@@ -796,12 +826,12 @@ load1:
                                         */
                                        rc = bdb_fix_dn( (*eip)->bei_e, 1 );
                                        if ( rc ) {
-                                               bdb_cache_entry_db_relock( bdb->bi_dbenv,
+                                               bdb_cache_entry_db_relock( bdb,
                                                        locker, *eip, 1, 0, lock );
                                                /* check again in case other modifier did it already */
                                                if ( bdb_fix_dn( (*eip)->bei_e, 1 ) )
                                                        rc = bdb_fix_dn( (*eip)->bei_e, 2 );
-                                               bdb_cache_entry_db_relock( bdb->bi_dbenv,
+                                               bdb_cache_entry_db_relock( bdb,
                                                        locker, *eip, 0, 0, lock );
                                        }
 #endif
@@ -814,6 +844,7 @@ load1:
                bdb_cache_entryinfo_unlock( *eip );
        }
        if ( ep ) {
+               ep->e_private = NULL;
 #ifdef SLAP_ZONE_ALLOC
                bdb_entry_return( bdb, ep, (*eip)->bei_zseq );
 #else
@@ -821,31 +852,17 @@ load1:
 #endif
        }
        if ( rc == 0 ) {
+               int purge = 0;
 
                if ( load ) {
-                       ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
+                       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
                        bdb->bi_cache.c_cursize++;
-                       ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
-               }
-
-               ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_head_mutex );
-
-               /* If the LRU list has only one entry and this is it, it
-                * doesn't need to be added again.
-                */
-               if ( bdb->bi_cache.c_lruhead == bdb->bi_cache.c_lrutail &&
-                       bdb->bi_cache.c_lruhead == *eip ) {
-                       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
-               } else {
-                       /* if entry is on LRU list, remove from old spot */
-                       if ( (*eip)->bei_lrunext || (*eip)->bei_lruprev ) {
-                               ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_tail_mutex );
-                               LRU_DELETE( &bdb->bi_cache, *eip );
-                               ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_tail_mutex );
-                       }
-                       /* lru_head_mutex is unlocked for us */
-                       bdb_cache_lru_add( bdb, *eip );
+                       if ( bdb->bi_cache.c_cursize > bdb->bi_cache.c_maxsize )
+                               purge = 1;
+                       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );
                }
+               if ( purge )
+                       bdb_cache_lru_purge( bdb );
        }
 
 #ifdef SLAP_ZONE_ALLOC
@@ -885,11 +902,11 @@ bdb_cache_add(
        EntryInfo *eip,
        Entry *e,
        struct berval *nrdn,
-       u_int32_t locker )
+       u_int32_t locker,
+       DB_LOCK *lock )
 {
        EntryInfo *new, ei;
-       DB_LOCK lock;
-       int rc;
+       int rc, purge = 0;
 #ifdef BDB_HIER
        struct berval rdn = e->e_name;
 #endif
@@ -902,7 +919,7 @@ bdb_cache_add(
        /* Lock this entry so that bdb_add can run to completion.
         * It can only fail if BDB has run out of lock resources.
         */
-       rc = bdb_cache_entry_db_lock( bdb->bi_dbenv, locker, &ei, 1, 0, &lock );
+       rc = bdb_cache_entry_db_lock( bdb, locker, &ei, 0, 0, lock );
        if ( rc ) {
                bdb_cache_entryinfo_unlock( eip );
                return rc;
@@ -930,37 +947,38 @@ bdb_cache_add(
        }
        new->bei_e = e;
        e->e_private = new;
-       new->bei_state = CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
+       new->bei_state |= CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
        eip->bei_state &= ~CACHE_ENTRY_NO_KIDS;
        if (eip->bei_parent) {
                eip->bei_parent->bei_state &= ~CACHE_ENTRY_NO_GRANDKIDS;
        }
        bdb_cache_entryinfo_unlock( eip );
 
-       ++bdb->bi_cache.c_cursize;
        ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
+       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
+       ++bdb->bi_cache.c_cursize;
+       if ( bdb->bi_cache.c_cursize > bdb->bi_cache.c_maxsize )
+               purge = 1;
+       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );
 
-       /* set lru mutex */
-       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_head_mutex );
-
-       /* lru_head_mutex is unlocked for us */
-       bdb_cache_lru_add( bdb, new );
+       if ( purge )
+               bdb_cache_lru_purge( bdb );
 
        return rc;
 }
 
 int
 bdb_cache_modify(
+       struct bdb_info *bdb,
        Entry *e,
        Attribute *newAttrs,
-       DB_ENV *env,
        u_int32_t locker,
        DB_LOCK *lock )
 {
        EntryInfo *ei = BEI(e);
        int rc;
        /* Get write lock on data */
-       rc = bdb_cache_entry_db_relock( env, locker, ei, 1, 0, lock );
+       rc = bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );
 
        /* If we've done repeated mods on a cached entry, then e_attrs
         * is no longer contiguous with the entry, and must be freed.
@@ -994,7 +1012,7 @@ bdb_cache_modrdn(
 #endif
 
        /* Get write lock on data */
-       rc =  bdb_cache_entry_db_relock( bdb->bi_dbenv, locker, ei, 1, 0, lock );
+       rc =  bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );
        if ( rc ) return rc;
 
        /* If we've done repeated mods on a cached entry, then e_attrs
@@ -1019,6 +1037,10 @@ bdb_cache_modrdn(
        avl_delete( &pei->bei_kids, (caddr_t) ei, bdb_rdn_cmp );
        free( ei->bei_nrdn.bv_val );
        ber_dupbv( &ei->bei_nrdn, nrdn );
+
+       if ( !pei->bei_kids )
+               pei->bei_state |= CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
+
 #ifdef BDB_HIER
        free( ei->bei_rdn.bv_val );
 
@@ -1029,6 +1051,8 @@ bdb_cache_modrdn(
                rdn.bv_len = ptr - rdn.bv_val;
        }
        ber_dupbv( &ei->bei_rdn, &rdn );
+       pei->bei_ckids--;
+       if ( pei->bei_dkids ) pei->bei_dkids--;
 #endif
 
        if (!ein) {
@@ -1038,7 +1062,16 @@ bdb_cache_modrdn(
                bdb_cache_entryinfo_unlock( pei );
                bdb_cache_entryinfo_lock( ein );
        }
+       /* parent now has kids */
+       if ( ein->bei_state & CACHE_ENTRY_NO_KIDS )
+               ein->bei_state ^= CACHE_ENTRY_NO_KIDS;
+
 #ifdef BDB_HIER
+       /* parent might now have grandkids */
+       if ( ein->bei_state & CACHE_ENTRY_NO_GRANDKIDS &&
+               !(ei->bei_state & (CACHE_ENTRY_NO_KIDS)))
+               ein->bei_state ^= CACHE_ENTRY_NO_GRANDKIDS;
+
        {
                /* Record the generation number of this change */
                ldap_pvt_thread_mutex_lock( &bdb->bi_modrdns_mutex );
@@ -1046,6 +1079,8 @@ bdb_cache_modrdn(
                ei->bei_modrdns = bdb->bi_modrdns;
                ldap_pvt_thread_mutex_unlock( &bdb->bi_modrdns_mutex );
        }
+       ein->bei_ckids++;
+       if ( ein->bei_dkids ) ein->bei_dkids++;
 #endif
        avl_insert( &ein->bei_kids, ei, bdb_rdn_cmp, avl_dup_error );
        bdb_cache_entryinfo_unlock( ein );
@@ -1060,9 +1095,8 @@ bdb_cache_modrdn(
  */
 int
 bdb_cache_delete(
-    Cache      *cache,
+       struct bdb_info *bdb,
     Entry              *e,
-    DB_ENV     *env,
     u_int32_t  locker,
     DB_LOCK    *lock )
 {
@@ -1078,7 +1112,7 @@ bdb_cache_delete(
        bdb_cache_entryinfo_lock( ei );
 
        /* Get write lock on the data */
-       rc = bdb_cache_entry_db_relock( env, locker, ei, 1, 0, lock );
+       rc = bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );
        if ( rc ) {
                /* couldn't lock, undo and give up */
                ei->bei_state ^= CACHE_ENTRY_DELETED;
@@ -1090,18 +1124,12 @@ bdb_cache_delete(
                e->e_id, 0, 0 );
 
        /* set lru mutex */
-       ldap_pvt_thread_mutex_lock( &cache->lru_tail_mutex );
-
-       /* set cache write lock */
-       ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
-
-       rc = bdb_cache_delete_internal( cache, e->e_private, 1 );
+       ldap_pvt_thread_mutex_lock( &bdb->bi_cache.lru_head_mutex );
 
-       /* free cache write lock */
-       ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+       rc = bdb_cache_delete_internal( &bdb->bi_cache, e->e_private, 1 );
 
        /* free lru mutex */
-       ldap_pvt_thread_mutex_unlock( &cache->lru_tail_mutex );
+       ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
 
        /* Leave entry info locked */
 
@@ -1136,10 +1164,10 @@ bdb_cache_delete_cleanup(
        ei->bei_kids = NULL;
        ei->bei_lruprev = NULL;
 
-       ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
+       ldap_pvt_thread_mutex_lock( &cache->c_eifree_mutex );
        ei->bei_lrunext = cache->c_eifree;
        cache->c_eifree = ei;
-       ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+       ldap_pvt_thread_mutex_unlock( &cache->c_eifree_mutex );
        bdb_cache_entryinfo_unlock( ei );
 }
 
@@ -1150,6 +1178,7 @@ bdb_cache_delete_internal(
     int                decr )
 {
        int rc = 0;     /* return code */
+       int decr_leaf = 0;
 
        /* Lock the parent's kids tree */
        bdb_cache_entryinfo_lock( e->bei_parent );
@@ -1165,22 +1194,39 @@ bdb_cache_delete_internal(
                rc = -1;
        }
        if ( e->bei_parent->bei_kids )
-               cache->c_leaves--;
+               decr_leaf = 1;
 
+       bdb_cache_entryinfo_unlock( e->bei_parent );
+
+       ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
        /* id tree */
-       if ( avl_delete( &cache->c_idtree, (caddr_t) e, bdb_id_cmp ) == NULL ) {
+       if ( avl_delete( &cache->c_idtree, (caddr_t) e, bdb_id_cmp )) {
+               cache->c_eiused--;
+               if ( decr_leaf )
+                       cache->c_leaves--;
+       } else {
                rc = -1;
        }
+       ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
 
        if ( rc == 0 ){
-               cache->c_eiused--;
-
                /* lru */
-               LRU_DELETE( cache, e );
-               if ( e->bei_e ) cache->c_cursize--;
-       }
+               if ( e == cache->c_lruhead ) cache->c_lruhead = e->bei_lrunext;
+               if ( e == cache->c_lrutail ) {
+                       ldap_pvt_thread_mutex_lock( &cache->lru_tail_mutex );
+                       if ( e == cache->c_lrutail ) cache->c_lrutail = e->bei_lruprev;
+                       ldap_pvt_thread_mutex_unlock( &cache->lru_tail_mutex );
+               }
 
-       bdb_cache_entryinfo_unlock( e->bei_parent );
+               if ( e->bei_lrunext ) e->bei_lrunext->bei_lruprev = e->bei_lruprev;
+               if ( e->bei_lruprev ) e->bei_lruprev->bei_lrunext = e->bei_lrunext;
+
+               if ( e->bei_e ) {
+                       ldap_pvt_thread_mutex_lock( &cache->c_count_mutex );
+                       cache->c_cursize--;
+                       ldap_pvt_thread_mutex_unlock( &cache->c_count_mutex );
+               }
+       }
 
        return( rc );
 }
@@ -1240,15 +1286,22 @@ bdb_lru_print( Cache *cache )
 {
        EntryInfo       *e;
 
-       fprintf( stderr, "LRU queue (head to tail):\n" );
-       for ( e = cache->c_lruhead; e != NULL; e = e->bei_lrunext ) {
-               fprintf( stderr, "\trdn \"%20s\" id %ld\n",
-                       e->bei_nrdn.bv_val, e->bei_id );
+       fprintf( stderr, "LRU circle head: %p\n", cache->c_lruhead );
+       fprintf( stderr, "LRU circle (tail forward):\n" );
+       for ( e = cache->c_lrutail; ; ) {
+               fprintf( stderr, "\t%p, %p id %ld rdn \"%s\"\n",
+                       e, e->bei_e, e->bei_id, e->bei_nrdn.bv_val );
+               e = e->bei_lrunext;
+               if ( e == cache->c_lrutail )
+                       break;
        }
-       fprintf( stderr, "LRU queue (tail to head):\n" );
-       for ( e = cache->c_lrutail; e != NULL; e = e->bei_lruprev ) {
-               fprintf( stderr, "\trdn \"%20s\" id %ld\n",
-                       e->bei_nrdn.bv_val, e->bei_id );
+       fprintf( stderr, "LRU circle (tail backward):\n" );
+       for ( e = cache->c_lrutail; ; ) {
+               fprintf( stderr, "\t%p, %p id %ld rdn \"%s\"\n",
+                       e, e->bei_e, e->bei_id, e->bei_nrdn.bv_val );
+               e = e->bei_lruprev;
+               if ( e == cache->c_lrutail )
+                       break;
        }
 }
 #endif
@@ -1323,29 +1376,3 @@ bdb_locker_id( Operation *op, DB_ENV *env, u_int32_t *locker )
        return 0;
 }
 #endif /* BDB_REUSE_LOCKERS */
-
-void
-bdb_cache_delete_entry(
-       struct bdb_info *bdb,
-       EntryInfo *ei,
-       u_int32_t locker,
-       DB_LOCK *lock )
-{
-       ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
-       if ( bdb_cache_entry_db_lock( bdb->bi_dbenv, bdb->bi_cache.c_locker, ei, 1, 1, lock ) == 0 )
-       {
-               if ( ei->bei_e && !(ei->bei_state & CACHE_ENTRY_NOT_LINKED )) {
-                       LRU_DELETE( &bdb->bi_cache, ei );
-                       ei->bei_e->e_private = NULL;
-#ifdef SLAP_ZONE_ALLOC
-                       bdb_entry_return( bdb, ei->bei_e, ei->bei_zseq );
-#else
-                       bdb_entry_return( ei->bei_e );
-#endif
-                       ei->bei_e = NULL;
-                       --bdb->bi_cache.c_cursize;
-               }
-               bdb_cache_entry_db_unlock( bdb->bi_dbenv, lock );
-       }
-       ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
-}