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2.3 back-bdb, cachesize, idlcachesize, and real memory usage

This has been asked before, but I didn't find any answers on it.

I'm trying to find a good way to predict the size of a slapd process
based on cachesize and idlcachesize.  (db_stat -m already gives me
info on the DB_CONFIG part of memory usage).

I was hoping to come up with a formula based on the <average text size
of an entry in my database> * <SOMESTUFF> * <(idl)cachesize setting>=
XXX bytes.

Do I just figure out the "sizeof" the structs below?

Any tips are appreciated.

In back-bdb.h, I found this:
/* for the in-core cache of entries */
typedef struct bdb_cache {
	int             c_maxsize;
	int             c_cursize;
	int		c_minfree;
	int		c_eiused;	/* EntryInfo's in use */
	int		c_leaves;	/* EntryInfo leaf nodes */
	EntryInfo	c_dntree;
	EntryInfo	*c_eifree;	/* free list */
	Avlnode         *c_idtree;
	EntryInfo	*c_lruhead;	/* lru - add accessed entries here */
	EntryInfo	*c_lrutail;	/* lru - rem lru entries from here */
	ldap_pvt_thread_rdwr_t c_rwlock;
	ldap_pvt_thread_mutex_t lru_head_mutex;
	ldap_pvt_thread_mutex_t lru_tail_mutex;
	u_int32_t	c_locker;	/* used by lru cleaner */
	void *c_zctx;
} Cache;

typedef struct bdb_idl_cache_entry_s {
	struct berval kstr;
	ldap_pvt_thread_rdwr_t idl_entry_rwlock;
	ID      *idl;
	DB      *db;
	struct bdb_idl_cache_entry_s* idl_lru_prev;
	struct bdb_idl_cache_entry_s* idl_lru_next;
} bdb_idl_cache_entry_t;

When I looked at an old core file with strings, I found a lot of dn's,
so I assume this was part of the cache.