Use a generic implementation of the Fowler/Noll/Vo hash (FNV hash).

Make the name cache hash as well as the nfsnode hash use it.

As a special tweak, create an unsigned version of register_t.  This allows
us to use a special tweak for the 64 bit versions that significantly
speeds up the i386 version (ie: int64 XOR int64 is slower than int64
XOR int32).

The code layout is a little strange for the string function, but I was
able to get between 5 to 10% improvement over the original version I
started with. The layout affects gcc code generation choices and this way
was fastest on x86 and alpha.

Note that 'CPUTYPE=p3' etc makes a fair difference to this.  It is
around 45% faster with -march=pentiumpro on a p6 cpu.

1 files changed, 6 insertions, 13 deletions

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 6657523..3f92c8f 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -48,6 +48,7 @@
 #include <sys/sysproto.h>
 #include <sys/proc.h>
 #include <sys/filedesc.h>
+#include <sys/fnv_hash.h>
 
 /*
  * This structure describes the elements in the cache of recent
@@ -180,9 +181,7 @@ cache_lookup(dvp, vpp, cnp)
 	struct componentname *cnp;
 {
 	struct namecache *ncp;
-	u_long hash;
-	u_char *cp;
-	int len;
+	u_int32_t hash;
 
 	if (!doingcache) {
 		cnp->cn_flags &= ~MAKEENTRY;
@@ -209,10 +208,7 @@ cache_lookup(dvp, vpp, cnp)
 		}
 	}
 
-	hash = 0;
-	len = cnp->cn_namelen;
-	for (cp = cnp->cn_nameptr; len; len--, cp++)
-		hash += *cp;
+	hash = fnv32_hashbuf(cnp->cn_nameptr, cnp->cn_namelen);
 	LIST_FOREACH(ncp, (NCHHASH(dvp, hash)), nc_hash) {
 		numchecks++;
 		if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
@@ -279,8 +275,7 @@ cache_enter(dvp, vp, cnp)
 {
 	struct namecache *ncp;
 	struct nchashhead *ncpp;
-	u_long hash;
-	u_char *cp, *dp;
+	u_int32_t hash;
 	int len;
 
 	if (!doingcache)
@@ -323,10 +318,8 @@ cache_enter(dvp, vp, cnp)
 	ncp->nc_vp = vp;
 	ncp->nc_dvp = dvp;
 	len = ncp->nc_nlen = cnp->cn_namelen;
-	hash = 0;
-	dp = ncp->nc_name;
-	for (cp = cnp->cn_nameptr; len; len--, cp++, dp++)
-		hash += (*dp = *cp);
+	hash = fnv32_hashbuf(cnp->cn_nameptr, len);
+	bcopy(cnp->cn_nameptr, ncp->nc_name, len);
 	ncpp = NCHHASH(dvp, hash);
 	LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
 	if (LIST_EMPTY(&dvp->v_cache_src))