vm_domainset: Simplify vm_domainset_iter_next()

As we are now visiting each domain only once, the test in
vm_domainset_iter_prefer() about skipping the preferred domain (the one
initially visited for policy DOMAINSET_POLICY_PREFER) becomes redundant.
Removing it makes this function essentially the same as
vm_domainset_iter_rr().

Thus, remove vm_domainset_iter_prefer().  This makes all policies behave
the same in vm_domainset_iter_next().

No functional change (intended).

PR:             277476
MFC after:      10 days
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D51250

1 files changed, 2 insertions, 30 deletions

diff --git a/sys/vm/vm_domainset.c b/sys/vm/vm_domainset.c
index bd15449559a5..a46dbe5ae92e 100644
--- a/sys/vm/vm_domainset.c
+++ b/sys/vm/vm_domainset.c
@@ -101,23 +101,12 @@ static void
 vm_domainset_iter_rr(struct vm_domainset_iter *di, int *domain)
 {
 
+	/* Grab the next domain in 'ds_order'. */
 	*domain = di->di_domain->ds_order[
 	    ++(*di->di_iter) % di->di_domain->ds_cnt];
 }
 
 static void
-vm_domainset_iter_prefer(struct vm_domainset_iter *di, int *domain)
-{
-	int d;
-
-	do {
-		d = di->di_domain->ds_order[
-		    ++(*di->di_iter) % di->di_domain->ds_cnt];
-	} while (d == di->di_domain->ds_prefer);
-	*domain = d;
-}
-
-static void
 vm_domainset_iter_interleave(struct vm_domainset_iter *di, int *domain)
 {
 	int d;
@@ -133,24 +122,7 @@ vm_domainset_iter_next(struct vm_domainset_iter *di, int *domain)
 
 	KASSERT(!DOMAINSET_EMPTY(&di->di_remain_mask),
 	    ("%s: Already iterated on all domains", __func__));
-	switch (di->di_policy) {
-	case DOMAINSET_POLICY_FIRSTTOUCH:
-		/*
-		 * To prevent impossible allocations we convert an invalid
-		 * first-touch to round-robin.
-		 */
-		/* FALLTHROUGH */
-	case DOMAINSET_POLICY_INTERLEAVE:
-		/* FALLTHROUGH */
-	case DOMAINSET_POLICY_ROUNDROBIN:
-		vm_domainset_iter_rr(di, domain);
-		break;
-	case DOMAINSET_POLICY_PREFER:
-		vm_domainset_iter_prefer(di, domain);
-		break;
-	default:
-		panic("%s: Unknown policy %d", __func__, di->di_policy);
-	}
+	vm_domainset_iter_rr(di, domain);
 	KASSERT(*domain < vm_ndomains,
 	    ("%s: Invalid domain %d", __func__, *domain));
 }