Reduce the limit of vnodes on i386 when ZFS is loaded to 3/4 of the original

value, so we don't run out of KVA. The default vnodes limit fits better for
UFS, but ZFS allocated more file system specific memory for a vnode than UFS.

Don't touch vnodes limit if we detect it was tuned by system administrator
and restore original value when ZFS is unloaded.

This isn't final fix, but before we implement something better, this will
help to stabilize ZFS under heavy load on i386.

Approved by:	re (bmah)

1 files changed, 41 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
index 259b77c..e08785a 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
@@ -949,6 +949,39 @@ zfs_freevfs(vfs_t *vfsp)
 	atomic_add_32(&zfs_active_fs_count, -1);
 }
 
+#ifdef __i386__
+static int desiredvnodes_backup;
+#endif
+
+static void
+zfs_vnodes_adjust(void)
+{
+#ifdef __i386__
+	int val;
+
+	desiredvnodes_backup = desiredvnodes;
+
+	/*
+	 * We calculate newdesiredvnodes the same way it is done in
+	 * vntblinit(). If it is equal to desiredvnodes, it means that
+	 * it wasn't tuned by the administrator and we can tune it down.
+	 */
+	val = min(maxproc + cnt.v_page_count / 4, 2 * vm_kmem_size /
+	    (5 * (sizeof(struct vm_object) + sizeof(struct vnode))));
+	if (desiredvnodes == val)
+		desiredvnodes = (3 * desiredvnodes) / 4;
+#endif
+}
+
+static void
+zfs_vnodes_adjust_back(void)
+{
+
+#ifdef __i386__
+	desiredvnodes = desiredvnodes_backup;
+#endif
+}
+
 void
 zfs_init(void)
 {
@@ -964,6 +997,13 @@ zfs_init(void)
 	 * Initialize znode cache, vnode ops, etc...
 	 */
 	zfs_znode_init();
+
+	/*
+	 * Reduce number of vnodes. Originally number of vnodes is calculated
+	 * with UFS inode in mind. We reduce it here, because it's too big for
+	 * ZFS/i386.
+	 */
+	zfs_vnodes_adjust();
 }
 
 void
@@ -971,6 +1011,7 @@ zfs_fini(void)
 {
 	zfsctl_fini();
 	zfs_znode_fini();
+	zfs_vnodes_adjust_back();
 }
 
 int