svn commit: r281677 - head/sys/kern

[Kirk McKusick]

Author: mckusick
Date: Sat Apr 18 00:59:03 2015
New Revision: 281677
URL: https://svnweb.freebsd.org/changeset/base/281677

Log:
  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

Modified:
  head/sys/kern/vfs_cache.c

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c	Sat Apr 18 00:53:52 2015	(r281676)
+++ head/sys/kern/vfs_cache.c	Sat Apr 18 00:59:03 2015	(r281677)
@@ -323,29 +323,25 @@ static SYSCTL_NODE(_debug, OID_AUTO, has
 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_HAND
 	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_HAND
 	/* 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)