More accurately collect name-cache statistics in sysctl functions

sysctl_debug_hashstat_nchash() and sysctl_debug_hashstat_rawnchash().
These changes are in preparation for allowing changes in the size
of the vnode hash tables driven by increases and decreases in the
maximum number of vnodes in the system.

Reviewed by: kib@
Phabric:     D2265

1 files changed, 16 insertions, 20 deletions

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index d57dc90..42d32e7 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -323,29 +323,25 @@ static SYSCTL_NODE(_debug, OID_AUTO, hashstat, CTLFLAG_RW, NULL,
 static int
 sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
 {
-	int error;
 	struct nchashhead *ncpp;
 	struct namecache *ncp;
-	int n_nchash;
-	int count;
+	int i, error, n_nchash, *cntbuf;
 
 	n_nchash = nchash + 1;	/* nchash is max index, not count */
-	if (!req->oldptr)
+	if (req->oldptr == NULL)
 		return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
-
-	/* Scan hash tables for applicable entries */
-	for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
-		CACHE_RLOCK();
-		count = 0;
-		LIST_FOREACH(ncp, ncpp, nc_hash) {
-			count++;
-		}
-		CACHE_RUNLOCK();
-		error = SYSCTL_OUT(req, &count, sizeof(count));
-		if (error)
-			return (error);
-	}
-	return (0);
+	cntbuf = malloc(n_nchash * sizeof(int), M_TEMP, M_ZERO | M_WAITOK);
+	CACHE_RLOCK();
+	/* Scan hash tables counting entries */
+	for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
+		LIST_FOREACH(ncp, ncpp, nc_hash)
+			cntbuf[i]++;
+	CACHE_RUNLOCK();
+	for (error = 0, i = 0; i < n_nchash; i++)
+		if ((error = SYSCTL_OUT(req, &cntbuf[i], sizeof(int))) != 0)
+			break;
+	free(cntbuf, M_TEMP);
+	return (error);
 }
 SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
     CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_rawnchash, "S,int",
@@ -363,6 +359,7 @@ sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
 	if (!req->oldptr)
 		return SYSCTL_OUT(req, 0, 4 * sizeof(int));
 
+	CACHE_RLOCK();
 	n_nchash = nchash + 1;	/* nchash is max index, not count */
 	used = 0;
 	maxlength = 0;
@@ -370,17 +367,16 @@ sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
 	/* Scan hash tables for applicable entries */
 	for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
 		count = 0;
-		CACHE_RLOCK();
 		LIST_FOREACH(ncp, ncpp, nc_hash) {
 			count++;
 		}
-		CACHE_RUNLOCK();
 		if (count)
 			used++;
 		if (maxlength < count)
 			maxlength = count;
 	}
 	n_nchash = nchash + 1;
+	CACHE_RUNLOCK();
 	pct = (used * 100) / (n_nchash / 100);
 	error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
 	if (error)