From: Vitaliy Makkoveev <mvs@openbsd.org>
Subject: vmstat(8): get rid of KERN_MALLOC_BUCKETS sysctl(2) call
To: tech@openbsd.org, Claudio Jeker <claudio@openbsd.org>
Date: Tue, 14 Jan 2025 14:08:38 +0300

claudio@ pointed that KERN_MALLOC_BUCKETS aka kern.malloc.buckets is just
the dummy string representation of (1 << i) for MINBUCKET to MINBUCKET +
16 integers, so no reason to keep it in kernel. Also tb@ pointed, that
Debian code search has no hits, so it's probably unused.

Let's try to remove it. Our vmstat(8) and systat(a) are the only
userland users and they could generate desired bucket names by them self
instead of KERN_MALLOC_BUCKETS strtonum(3) parsing.

This diff converts vmstat(8). I'll convert systat(1) separately if this
conversion will be accepted.

Note, MINBUCKET and MAXBUCKET are defined in kernel headers, the
"MINBUCKET + 16" is already hard-coded to vmstat.c.

Note, sysctl_malloc() has the similar KERN_MALLOC_KMEMNAMES string,
which is unused in our userland and also was not found by Debian code
search.

Index: usr.bin/vmstat/vmstat.c
===================================================================
RCS file: /cvs/src/usr.bin/vmstat/vmstat.c,v
retrieving revision 1.158
diff -u -p -r1.158 vmstat.c
--- usr.bin/vmstat/vmstat.c	1 May 2024 12:54:27 -0000	1.158
+++ usr.bin/vmstat/vmstat.c	14 Jan 2025 10:39:58 -0000
@@ -735,43 +735,22 @@ domem(void)
 	struct kmemstats kmemstats[M_LAST], *ks;
 	int i, j, len, size, first, mib[4];
 	u_long totuse = 0, totfree = 0;
-	char buf[BUFSIZ], *bufp, *ap;
 	unsigned long long totreq = 0;
 	const char *name;
 	size_t siz;
 
-	if (memf == NULL && nlistf == NULL) {
-		mib[0] = CTL_KERN;
-		mib[1] = KERN_MALLOCSTATS;
-		mib[2] = KERN_MALLOC_BUCKETS;
-		siz = sizeof(buf);
-		if (sysctl(mib, 3, buf, &siz, NULL, 0) == -1) {
-			warnx("could not read kern.malloc.buckets");
-			return;
-		}
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_MALLOCSTATS;
+	mib[2] = KERN_MALLOC_BUCKET;
+	siz = sizeof(struct kmembuckets);
 
-		bufp = buf;
-		mib[2] = KERN_MALLOC_BUCKET;
-		siz = sizeof(struct kmembuckets);
-		i = 0;
-		while ((ap = strsep(&bufp, ",")) != NULL) {
-			const char *errstr;
+	for (i = MINBUCKET; i < MINBUCKET + 16; i++) {
+		mib[3] = (1<<i);
 
-			mib[3] = strtonum(ap, 0, INT_MAX, &errstr);
-			if (errstr) {
-				warnx("kernel lied about %d being a number", mib[3]);
-				return;
-			}
-
-			if (sysctl(mib, 4, &buckets[MINBUCKET + i], &siz,
-			    NULL, 0) == -1) {
-				warn("could not read kern.malloc.bucket.%d", mib[3]);
-				return;
-			}
-			i++;
+		if (sysctl(mib, 4, &buckets[i], &siz, NULL, 0) == -1) {
+			warn("could not read kern.malloc.bucket.%d", mib[3]);
+			return;
 		}
-	} else {
-		kread(X_KMEMBUCKETS, buckets, sizeof(buckets));
 	}
 
 	for (first = 1, i = MINBUCKET, kp = &buckets[i]; i < MINBUCKET + 16;