#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
#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(
int tryOnly,
DB_LOCK *lock )
{
-#ifdef NO_THREADS
+#ifdef NO_DB_LOCK
return 0;
#else
int rc;
bdb_cache_entry_db_lock( DB_ENV *env, 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;
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 )
{
-#ifdef NO_THREADS
+#ifdef NO_DB_LOCK
return 0;
#else
int rc;
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 )
ei->bei_parent->bei_ckids++;
#endif
}
+ bdb_cache_lru_link( &bdb->bi_cache, ei2 );
*res = ei2;
return 0;
}
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 ) {
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;
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 );
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
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;
+
+ /* Reset all the state info */
+ for (ein = eir; ein != ei2; ein=ein->bei_parent)
+ ein->bei_state &= ~CACHE_ENTRY_NOT_LINKED;
+
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;
*res = eir;
break;
}
}
#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;
-
- LRU_ADD( &bdb->bi_cache, ei );
- ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
+ EntryInfo *elru, *elnext;
+ int count, islocked;
- /* See if we're above the cache size limit */
- if ( bdb->bi_cache.c_cursize <= bdb->bi_cache.c_maxsize )
+ /* Don't bother if we can't get the lock */
+ if ( ldap_pvt_thread_mutex_trylock( &bdb->bi_cache.lru_head_mutex ) )
return;
- if ( bdb->bi_cache.c_locker ) {
- lockp = &lock;
- } else {
- lockp = NULL;
- }
-
- /* Don't bother if we can't get the lock */
- if ( ldap_pvt_thread_mutex_trylock( &bdb->bi_cache.lru_tail_mutex ) )
+ if ( bdb->bi_cache.c_cursize <= bdb->bi_cache.c_maxsize ) {
+ ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
return;
+ }
+ 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;
- /* If we can successfully writelock it, then
- * the object is idle.
+ /* 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.
*/
- if ( bdb_cache_entry_db_lock( bdb->bi_dbenv,
- bdb->bi_cache.c_locker, elru, 1, 1, lockp ) == 0 ) {
+ if ( elru->bei_state & ( CACHE_ENTRY_NOT_LINKED |
+ CACHE_ENTRY_DELETED | CACHE_ENTRY_LOADING )) {
+ bdb_cache_entryinfo_unlock( elru );
+ continue;
+ }
+ islocked = 1;
- /* 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;
+ /* Free entry for this node if it's present */
+ if ( elru->bei_e ) {
+ elru->bei_e->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
- bdb_entry_return( bdb, elru->bei_e, elru->bei_zseq );
+ bdb_entry_return( bdb, elru->bei_e, elru->bei_zseq );
#else
- bdb_entry_return( elru->bei_e );
+ bdb_entry_return( elru->bei_e );
#endif
- elru->bei_e = NULL;
- count++;
- }
- /* ITS#4010 if we're in slapcat, and this node is a leaf
- * node, free it.
- *
- * FIXME: we need to do this for slapd as well, (which is
- * why we compute bi_cache.c_leaves now) but at the moment
- * we can't because it causes unresolvable deadlocks.
- */
- 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 );
- }
- /* Leave node on LRU list for a future pass */
- } else {
- LRU_DELETE( &bdb->bi_cache, elru );
+ elru->bei_e = NULL;
+ count++;
+ }
+ /* ITS#4010 if we're in slapcat, and this node is a leaf
+ * node, free it.
+ *
+ * FIXME: we need to do this for slapd as well, (which is
+ * why we compute bi_cache.c_leaves now) but at the moment
+ * we can't because it causes unresolvable deadlocks.
+ */
+ if ( slapMode & SLAP_TOOL_READONLY ) {
+ if ( !elru->bei_kids ) {
+ bdb_cache_delete_internal( &bdb->bi_cache, elru, 0 );
+ bdb_cache_delete_cleanup( &bdb->bi_cache, elru );
+ islocked = 0;
}
- bdb_cache_entry_db_unlock( bdb->bi_dbenv, lockp );
+ /* Leave node on LRU list for a future pass */
+ }
- if ( count >= bdb->bi_cache.c_minfree ) {
- ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
- bdb->bi_cache.c_cursize -= count;
- ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
- 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 = elru;
+ ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.lru_head_mutex );
}
EntryInfo *
#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
DB_LOCK *lock )
{
EntryInfo *new, ei;
- int rc;
+ int rc, purge = 0;
#ifdef BDB_HIER
struct berval rdn = e->e_name;
#endif
}
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;
}
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 );
+ ldap_pvt_thread_mutex_lock( &cache->lru_head_mutex );
rc = bdb_cache_delete_internal( cache, e->e_private, 1 );
- /* free cache write lock */
- ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
-
/* free lru mutex */
- ldap_pvt_thread_mutex_unlock( &cache->lru_tail_mutex );
+ ldap_pvt_thread_mutex_unlock( &cache->lru_head_mutex );
/* Leave entry info locked */
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 );
}
int decr )
{
int rc = 0; /* return code */
+ int decr_leaf = 0;
/* Lock the parent's kids tree */
bdb_cache_entryinfo_lock( e->bei_parent );
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 );
}
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 );
-}
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