sys/kern/vfs_cache.c

199  * - there is a simple scheme to evict negative entries as the cache is approaching
202  *   which loses the name cache entries when it perhaps should not. in case of tmpfs
210 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
211     "Name cache");
257  * This structure describes the elements in the cache of recent
285  * to be stored.  The nc_dotdottime field is used when a cache entry is mapping
407     "Name cache parameters");
442 static u_long __exclusive_cache_line	numcache;/* number of cache entries allocated */
444 struct nchstats	nchstats;		/* cache effectiveness statistics */
518 static int __read_mostly	doingcache = 1;	/* 1 => enable the cache */
528  * The new name cache statistics
531     "Name cache statistics");
539 STATNODE_ULONG(neg, numneg, "Number of negative cache entries");
540 STATNODE_ULONG(count, numcache, "Number of cache entries");
545 STATNODE_COUNTER(miss, nummiss, "Number of cache misses");
546 STATNODE_COUNTER(misszap, nummisszap, "Number of cache misses we do not want to cache");
548     "Number of cache hits (positive) we do not want to cache");
549 STATNODE_COUNTER(poshits, numposhits, "Number of cache hits (positive)");
551     "Number of cache hits (negative) we do not want to cache");
552 STATNODE_COUNTER(neghits, numneghits, "Number of cache hits (negative)");
560 STATNODE_COUNTER(symlinktoobig, symlinktoobig, "Number of times symlink did not fit the cache");
566     "Name cache debugging");
593 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
734 	 * (for example this can happen after a cache miss during concurrent
1003     "VFS cache effectiveness statistics");
1038  * Grab an atomic snapshot of the name cache hash chain lengths
1144     "Name cache negative entry statistics");
1147     "Number of negative cache entries");
1173     "Number of cache hits (negative)");
1513  * can comprise of negative entries. However, if the cache is just
1518  * Try evicting if the cache is close to full capacity regardless of
1540  *   Removes a namecache entry from cache, whether it contains an actual
1541  *   pointer to a vnode or if it is just a negative cache entry.
1912  * Lookup a name in the name cache
1917  * - vpp:	Return argument.  Will contain desired vnode on cache hit.
1920  *   	- MAKEENTRY:	If clear, free an entry from the cache rather than look
1923  * - tsp:	Return storage for cache timestamp.  On a successful (positive
1925  *   		was stored when this cache entry was created.  However, it will
1927  * - ticks:	Return storage for alternate cache timestamp.  On a successful
1929  *   		that was current when the cache entry was created, unless cnp
1936  * - -1:	A positive cache hit.  vpp will contain the desired vnode.
1937  * - ENOENT:	A negative cache hit, or dvp was recycled out from under us due
1941  * - 0:		A cache miss.  vpp will not be modified.
1945  * On a cache hit, vpp will be returned locked and ref'd.  If we're looking up
2251  * Lock part of the cache affected by the insertion.
2377  * Add an entry to the cache.
2456 	 * See if this vnode or negative entry is already in the cache
2519 			 * For this case, the cache entry maps both the
2547 	 * "negative" cache queue, otherwise, we place it into the
2548 	 * destination vnode's cache entries queue.
2564 	 * within the cache entries table.
2619  * Name cache initialization, from vfs_init() when we are booting
2678  * Induce transient cache misses for lockless operation in cache_lookup() by
2694 	 * result in a cache miss, which all callers are supposed to know how
2938 	 * the target file is immediately accessed after rename, inducing a cache
3012  * Perform canonical checks and cache lookup and pass on to filesystem
3127  * cache (if available)
5458 	 * resulting in cache misses.
5500 	 * be elided in the common case -- if an entry was found in the cache,