Try to stabilize ZFS with regard to memory consumption:

- Allow to shrink ARC down to 16MB (instead of 64MB).
- Set arc_max to 1/2 of kmem_map by default.
- Start freeing things earlier when low memory situation is detected.
- Serialize execution of arc_lowmem().

I decided to setup minimum ZFS memory requirements to 512MB of RAM and 256MB of
kmem_map size. If there is less RAM or kmem_map, a warning will be printed.
World is cruel, be no better. In other words: modern file system requires
modern hardware:)

From ZFS administration guide:

"Currently the minimum amount of memory recommended to install a Solaris
 system is 512 Mbytes. However, for good ZFS performance, at least one
 Gbyte or more of memory is recommended."

1 files changed, 22 insertions, 7 deletions

diff --git a/sys/cddl/compat/opensolaris/kern/opensolaris_kmem.c b/sys/cddl/compat/opensolaris/kern/opensolaris_kmem.c
index 2d6f3e5..a73349f 100644
--- a/sys/cddl/compat/opensolaris/kern/opensolaris_kmem.c
+++ b/sys/cddl/compat/opensolaris/kern/opensolaris_kmem.c
@@ -31,12 +31,19 @@ __FBSDID("$FreeBSD$");
 #include <sys/kernel.h>
 #include <sys/systm.h>
 #include <sys/malloc.h>
-#include <vm/uma.h>
 #include <sys/kmem.h>
 #include <sys/debug.h>
 #include <sys/mutex.h>
+
+#include <vm/vm_page.h>
+#include <vm/vm_object.h>
+#include <vm/vm_kern.h>
+#include <vm/vm_map.h>
+
+#ifdef KMEM_DEBUG
 #include <sys/queue.h>
 #include <sys/stack.h>
+#endif
 
 #ifdef _KERNEL
 static MALLOC_DEFINE(M_SOLARIS, "solaris", "Solaris");
@@ -82,12 +89,6 @@ zfs_kmem_alloc(size_t size, int kmflags)
 	return (p);
 }
 
-void *
-kmem_zalloc(size_t size, int kmflags)
-{
-	return (kmem_alloc(size, kmflags | M_ZERO));
-}
-
 void
 zfs_kmem_free(void *buf, size_t size __unused)
 {
@@ -107,6 +108,20 @@ zfs_kmem_free(void *buf, size_t size __unused)
 	free(buf, M_SOLARIS);
 }
 
+u_long
+kmem_size(void)
+{
+
+	return ((u_long)vm_kmem_size);
+}
+
+u_long
+kmem_used(void)
+{
+
+	return ((u_long)kmem_map->size);
+}
+
 static int
 kmem_std_constructor(void *mem, int size __unused, void *private, int flags)
 {