The pool garbage collection code only runs (from init_main.c) on
MULTIPROCESSOR kernels. The relevant code and global variables can be
omitted on single-processor kernels.

Index: kern/subr_pool.c
===================================================================
RCS file: /OpenBSD/src/sys/kern/subr_pool.c,v
diff -u -p -r1.243 subr_pool.c
--- kern/subr_pool.c	29 Jan 2026 01:04:35 -0000	1.243
+++ kern/subr_pool.c	24 Oct 2026 19:40:02 -0000
@@ -103,11 +103,13 @@ pl_enter(struct pool *pp, union pool_loc
 {
 	pp->pr_lock_ops->pl_enter(pl);
 }
+#ifdef MULTIPROCESSOR
 static inline int
 pl_enter_try(struct pool *pp, union pool_lock *pl)
 {
 	return pp->pr_lock_ops->pl_enter_try(pl);
 }
+#endif
 static inline void
 pl_leave(struct pool *pp, union pool_lock *pl)
 {
@@ -265,11 +267,13 @@ void	 pool_print1(struct pool *, const c
 	     __attribute__((__format__(__kprintf__,1,2))));
 #endif
 
+#ifdef MULTIPROCESSOR
 /* stale page garbage collectors */
 void	pool_gc_sched(void *);
 struct timeout pool_gc_tick = TIMEOUT_INITIALIZER(pool_gc_sched, NULL);
 void	pool_gc_pages(void *);
 struct task pool_gc_task = TASK_INITIALIZER(pool_gc_pages, NULL);
+#endif	/* MULTIPROCESSOR */
 
 #define POOL_WAIT_FREE	SEC_TO_NSEC(1)
 #define POOL_WAIT_GC	SEC_TO_NSEC(8)
@@ -1551,6 +1555,7 @@ sysctl_dopool(int *name, u_int namelen, 
 }
 #endif /* SMALL_KERNEL */
 
+#ifdef MULTIPROCESSOR
 void
 pool_gc_sched(void *null)
 {
@@ -1567,10 +1572,8 @@ pool_gc_pages(void *null)
 	rw_enter_read(&pool_lock);
 	s = splvm(); /* XXX go to splvm until all pools _setipl properly */
 	SIMPLEQ_FOREACH(pp, &pool_head, pr_poollist) {
-#ifdef MULTIPROCESSOR
 		if (pp->pr_cache != NULL)
 			pool_cache_gc(pp);
-#endif
 
 		if (pp->pr_nidle <= pp->pr_minpages || /* guess */
 		    !pl_enter_try(pp, &pp->pr_lock)) /* try */
@@ -1595,6 +1598,7 @@ pool_gc_pages(void *null)
 
 	timeout_add_sec(&pool_gc_tick, 1);
 }
+#endif	/* MULTIPROCESSOR */
 
 /*
  * Pool backend allocators.