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Make the VFS cache use zones instead of malloc(9). This results in a

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small but noticeable increase in performance for name lookup operations.

The code uses two zones, one for short names (less than 32 characters)
and one for long names (up to NAME_MAX).  Since most file names are
fairly short, this saves a considerable amount of space that would
otherwise be wasted if we always allocated NAME_MAX bytes.  The cutoff
value of 32 characters was picked arbitrarily and may benefit from some
tweaking; it could also be made into a tunable.

Submitted by:	hmp
This commit is contained in:
Dag-Erling Smørgrav 2003-06-13 08:46:13 +00:00
parent d7ae6bd221
commit c2935410f6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=116289
1 changed files with 33 additions and 4 deletions
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37
sys/kern/vfs_cache.c
View file

@ -55,6 +55,8 @@ __FBSDID("$FreeBSD$");
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <vm/uma.h>
/*
* This structure describes the elements in the cache of recent
* names looked up by namei.
@ -111,6 +113,28 @@ SYSCTL_ULONG(_debug, OID_AUTO, numcachepl, CTLFLAG_RD, &numcachepl, 0, "");
#endif
struct nchstats nchstats; /* cache effectiveness statistics */
/*
* UMA zones for the VFS cache.
*
* The small cache is used for entries with short names, which are the
* most common. The large cache is used for entries which are too big to
* fit in the small cache.
*/
static uma_zone_t cache_zone_small;
static uma_zone_t cache_zone_large;
#define CACHE_PATH_CUTOFF 32
#define CACHE_ZONE_SMALL (sizeof(struct namecache) + CACHE_PATH_CUTOFF)
#define CACHE_ZONE_LARGE (sizeof(struct namecache) + NAME_MAX)
#define cache_alloc(len) uma_zalloc(((len) <= CACHE_PATH_CUTOFF) ? \
cache_zone_small : cache_zone_large, M_WAITOK)
#define cache_free(ncp) do { \
if (ncp != NULL) \
uma_zfree(((ncp)->nc_nlen <= CACHE_PATH_CUTOFF) ? \
cache_zone_small : cache_zone_large, (ncp)); \
} while (0)
static int doingcache = 1; /* 1 => enable the cache */
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, "");
@ -253,7 +277,7 @@ cache_zap(ncp)
numneg--;
}
numcache--;
free(ncp, M_VFSCACHE);
cache_free(ncp);
}
/*
@ -418,9 +442,8 @@ cache_enter(dvp, vp, cnp)
}
}
ncp = (struct namecache *)
malloc(sizeof *ncp + cnp->cn_namelen, M_VFSCACHE, M_WAITOK);
bzero((char *)ncp, sizeof *ncp);
ncp = cache_alloc(cnp->cn_namelen);
/* XXX can uma_zalloc(..., M_WAITOK) fail? */
numcache++;
if (!vp) {
numneg++;
@ -472,6 +495,12 @@ nchinit(void *dummy __unused)
{
TAILQ_INIT(&ncneg);
cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL, NULL,
NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE, NULL,
NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL)