CVS commit: src/usr.sbin/pstat

[Alan Barrett]

Module Name:    src
Committed By:   apb
Date:           Sat Nov 10 11:01:52 UTC 2012

Modified Files:
        src/usr.sbin/pstat: pstat.c

Log Message:
The number of active vnodes may grow in between the sysctl call
that figures out the size, and the sysctl call that fetches the data.

Previously, any growth at all would have resulted in this error message:

        pstat: sysctl: KERN_VNODE: Cannot allocate memory

Now allow for growth of 100 vnodes, or 5%, or both.  Growth in
excess of 2% or 6000 vnodeshas been observed in practice.  Also
ignore ENOMEM from the second sysctl call, in case the growth was
even more than we anticipated.


To generate a diff of this commit:
cvs rdiff -u -r1.119 -r1.120 src/usr.sbin/pstat/pstat.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


Modified files:

Index: src/usr.sbin/pstat/pstat.c
diff -u src/usr.sbin/pstat/pstat.c:1.119 src/usr.sbin/pstat/pstat.c:1.120
--- src/usr.sbin/pstat/pstat.c:1.119	Mon Jun  4 20:13:47 2012
+++ src/usr.sbin/pstat/pstat.c	Sat Nov 10 11:01:52 2012
@@ -1,4 +1,4 @@
-/*	$NetBSD: pstat.c,v 1.119 2012/06/04 20:13:47 riastradh Exp $	*/
+/*	$NetBSD: pstat.c,v 1.120 2012/11/10 11:01:52 apb Exp $	*/
 
 /*-
  * Copyright (c) 1980, 1991, 1993, 1994
@@ -39,7 +39,7 @@ __COPYRIGHT("@(#) Copyright (c) 1980, 19
 #if 0
 static char sccsid[] = "@(#)pstat.c	8.16 (Berkeley) 5/9/95";
 #else
-__RCSID("$NetBSD: pstat.c,v 1.119 2012/06/04 20:13:47 riastradh Exp $");
+__RCSID("$NetBSD: pstat.c,v 1.120 2012/11/10 11:01:52 apb Exp $");
 #endif
 #endif /* not lint */
 
@@ -73,6 +73,7 @@ __RCSID("$NetBSD: pstat.c,v 1.119 2012/0
 #include <sys/sysctl.h>
 
 #include <err.h>
+#include <errno.h>
 #include <kvm.h>
 #include <limits.h>
 #include <nlist.h>
@@ -681,7 +682,8 @@ char *
 loadvnodes(int *avnodes)
 {
 	int mib[2];
-	size_t copysize;
+	int status;
+	size_t copysize, oldsize;
 	char *vnodebase;
 
 	if (totalflag) {
@@ -696,12 +698,34 @@ loadvnodes(int *avnodes)
 	}
 	mib[0] = CTL_KERN;
 	mib[1] = KERN_VNODE;
+	/*
+	 * First sysctl call gets the necessary buffer size; second
+	 * sysctl call gets the data.  We allow for some growth in the
+	 * data size between the two sysctl calls (increases of a few
+	 * thousand vnodes in between the two calls have been observed).
+	 * We ignore ENOMEM from the second sysctl call, which can
+	 * happen if the kernel's data grew by even more than we allowed
+	 * for.
+	 */
 	if (sysctl(mib, 2, NULL, &copysize, NULL, 0) == -1)
 		err(1, "sysctl: KERN_VNODE");
+	oldsize = copysize;
+	copysize += 100 * sizeof(struct vnode) + copysize / 20;
 	if ((vnodebase = malloc(copysize)) == NULL)
 		err(1, "malloc");
-	if (sysctl(mib, 2, vnodebase, &copysize, NULL, 0) == -1)
+	status = sysctl(mib, 2, vnodebase, &copysize, NULL, 0);
+	if (status == -1 && errno != ENOMEM)
 		err(1, "sysctl: KERN_VNODE");
+#if 0 /* for debugging the amount of growth allowed for */
+	if (copysize != oldsize) {
+		warnx("count changed from %ld to %ld (%+ld)%s",
+		    (long)(oldsize / sizeof(struct vnode)),
+		    (long)(copysize / sizeof(struct vnode)),
+		    (long)(copysize / sizeof(struct vnode)) -
+			(long)(oldsize / sizeof(struct vnode)),
+		    (status == 0 ? "" : ", and errno = ENOMEM"));
+	}
+#endif
 	if (copysize % (VPTRSZ + VNODESZ))
 		errx(1, "vnode size mismatch");
 	*avnodes = copysize / (VPTRSZ + VNODESZ);