Index: external/cddl/osnet/dist/uts/common/fs/zfs/arc.c
===================================================================
RCS file: /cvsroot/src/external/cddl/osnet/dist/uts/common/fs/zfs/arc.c,v
retrieving revision 1.22
diff -u -r1.22 arc.c
--- external/cddl/osnet/dist/uts/common/fs/zfs/arc.c	3 Aug 2022 01:53:06 -0000	1.22
+++ external/cddl/osnet/dist/uts/common/fs/zfs/arc.c	12 Dec 2025 10:57:52 -0000
@@ -6094,12 +6094,23 @@
 #endif	/* illumos */
 	/* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */
 	arc_c_min = MAX(arc_c / 4, arc_abs_min);
+
+#if defined(__NetBSD__) && defined(_KERNEL)
+	/*
+	 * Due to concerns about NetBSD/zfs and mechanisms for general
+	 * memory pressure to reduce ARC usage, limit arc_c_max to the
+	 * value computed for 1/8.  Additionally, limit it to 1/8 of
+	 * VM, similar to illumos above, to address the i386 case.
+	 */
+	arc_c_max = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
+#else
 	/* set max to 1/2 of all memory, or all but 1GB, whichever is more */
 	if (arc_c * 8 >= 1 << 30)
 		arc_c_max = (arc_c * 8) - (1 << 30);
 	else
 		arc_c_max = arc_c_min;
 	arc_c_max = MAX(arc_c * 5, arc_c_max);
+#endif
 
 	/*
 	 * In userland, there's only the memory pressure that we artificially
@@ -6135,8 +6146,16 @@
 	if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
 		arc_meta_limit = zfs_arc_meta_limit;
 
+#if defined(__NetBSD__)
+	/*
+	 * XXX Explain why this is reasonable; it appears to protect
+	 * the cache from going below half the max allowed amount of
+	 * metadata, and that is not obviously sensible.
+	 */
+#else
 	if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
 		arc_c_min = arc_meta_limit / 2;
+#endif
 
 	if (zfs_arc_meta_min > 0) {
 		arc_meta_min = zfs_arc_meta_min;
@@ -6218,6 +6237,13 @@
 		zfs_dirty_data_max = MIN(zfs_dirty_data_max,
 		    zfs_dirty_data_max_max);
 	}
+#if defined(__NetBSD__)
+	/*
+	 * XXX Disable prefetch if RAM is low.
+	 */
+	printf("zfs: disabling prefetch\n");
+	zfs_prefetch_disable = 1;
+#endif
 
 #ifdef _KERNEL
 #ifdef __FreeBSD__