Index: sys/uvm/uvm_glue.c
===================================================================
RCS file: /home/netbsd/src/sys/uvm/uvm_glue.c,v
retrieving revision 1.176
diff -p -u -r1.176 uvm_glue.c
--- sys/uvm/uvm_glue.c	12 Jan 2020 12:55:03 -0000	1.176
+++ sys/uvm/uvm_glue.c	18 Feb 2020 02:37:59 -0000
@@ -262,12 +262,11 @@ uarea_poolpage_alloc(struct pool *pp, in
 	}
 #endif
 #if defined(__HAVE_CPU_UAREA_ROUTINES)
-	void *va = cpu_uarea_alloc(false);
-	if (va)
-		return (void *)va;
-#endif
+	return cpu_uarea_alloc(false);
+#else
 	return (void *)uvm_km_alloc(kernel_map, pp->pr_alloc->pa_pagesz,
 	    USPACE_ALIGN, UVM_KMF_WIRED | UVM_KMF_WAITVA);
+#endif
 }
 
 static void
@@ -284,11 +283,12 @@ uarea_poolpage_free(struct pool *pp, voi
 	}
 #endif
 #if defined(__HAVE_CPU_UAREA_ROUTINES)
-	if (cpu_uarea_free(addr))
-		return;
-#endif
+	bool used __diagused = cpu_uarea_free(addr);
+	KASSERT(used);
+#else
 	uvm_km_free(kernel_map, (vaddr_t)addr, pp->pr_alloc->pa_pagesz,
 	    UVM_KMF_WIRED);
+#endif
 }
 
 static struct pool_allocator uvm_uarea_allocator = {
@@ -332,6 +332,13 @@ void
 uvm_uarea_init(void)
 {
 	int flags = PR_NOTOUCH;
+#if defined(__HAVE_CPU_UAREA_ROUTINES)
+	/*
+	 * Let pool subsystem know that cpu_uarea_alloc() may fail even for
+	 * PR_WAITOK, when no contiguous pages available.
+	 */
+	flags |= PR_MAYFAIL;
+#endif
 
 	/*
 	 * specify PR_NOALIGN unless the alignment provided by
Index: sys/uvm/uvm_pglist.c
===================================================================
RCS file: /home/netbsd/src/sys/uvm/uvm_pglist.c,v
retrieving revision 1.80
diff -p -u -r1.80 uvm_pglist.c
--- sys/uvm/uvm_pglist.c	20 Feb 2020 04:54:47 -0000	1.80
+++ sys/uvm/uvm_pglist.c	20 Feb 2020 06:33:36 -0000
@@ -310,8 +310,10 @@ uvm_pglistalloc_contig(int num, paddr_t 
 
 	/* Are there even any free pages? */
 	if (uvm_availmem() <=
-	    (uvmexp.reserve_pagedaemon + uvmexp.reserve_kernel))
+	    (uvmexp.reserve_pagedaemon + uvmexp.reserve_kernel)) {
+		printf("%s: no enough memory\n", __func__);
 		goto out;
+	}
 
 	for (fl = 0; fl < VM_NFREELIST; fl++) {
 #if (VM_PHYSSEG_STRAT == VM_PSTRAT_BIGFIRST)
@@ -337,6 +339,8 @@ uvm_pglistalloc_contig(int num, paddr_t 
 		}
 	}
 
+	printf("%s: no contiguous pages\n", __func__);
+
 out:
 	/*
 	 * check to see if we need to generate some free pages waking
Index: sys/kern/subr_pool.c
===================================================================
RCS file: /home/netbsd/src/sys/kern/subr_pool.c,v
retrieving revision 1.266
diff -p -u -r1.266 subr_pool.c
--- sys/kern/subr_pool.c	8 Feb 2020 07:07:07 -0000	1.266
+++ sys/kern/subr_pool.c	18 Feb 2020 02:37:59 -0000
@@ -1093,7 +1093,8 @@ pool_get(struct pool *pp, int flags)
 		pp->pr_nfail++;
 
 		mutex_exit(&pp->pr_lock);
-		KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0);
+		KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0 ||
+		    (pp->pr_roflags & PR_MAYFAIL) != 0);
 		return NULL;
 	}
 
@@ -1136,7 +1137,8 @@ pool_get(struct pool *pp, int flags)
 
 			pp->pr_nfail++;
 			mutex_exit(&pp->pr_lock);
-			KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0);
+			KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0 ||
+			    (pp->pr_roflags & PR_MAYFAIL) != 0);
 			return NULL;
 		}
 
@@ -2498,7 +2500,8 @@ pool_cache_get_slow(pool_cache_cpu_t *cc
 	object = pool_get(&pc->pc_pool, flags);
 	*objectp = object;
 	if (__predict_false(object == NULL)) {
-		KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0);
+		KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0 ||
+		    (pc->pc_pool.pr_roflags & PR_MAYFAIL) != 0);
 		return false;
 	}
 
Index: sys/sys/pool.h
===================================================================
RCS file: /home/netbsd/src/sys/sys/pool.h,v
retrieving revision 1.89
diff -p -u -r1.89 pool.h
--- sys/sys/pool.h	9 May 2019 08:16:15 -0000	1.89
+++ sys/sys/pool.h	21 Feb 2020 09:47:43 -0000
@@ -161,6 +161,7 @@ struct pool {
 #define	PR_GROWINGNOWAIT 0x4000	/* pool_grow in progress by PR_NOWAIT alloc */
 #define	PR_ZERO		0x8000	/* zero data before returning */
 #define	PR_USEBMAP	0x10000	/* use a bitmap to manage freed items */
+#define	PR_MAYFAIL	0x20000 /* allocator may fail even if WAITOK */
 
 	/*
 	 * `pr_lock' protects the pool's data structures when removing