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sys_attrs_ufs(5)					     sys_attrs_ufs(5)



NAME

  sys_attrs_ufs	- ufs subsystem	attributes

DESCRIPTION

  This reference page lists and	describes attributes for the UNIX File System
  (ufs)	kernel subsystem. Refer	to the sys_attrs(5) reference page for an
  introduction to the topic of kernel subsystem	attributes.



  create_fastlinks
      A	value that enables (1) or disables (0) the creation of fast symbolic
      link files.

      Default value: 1 (enabled)



  inode_hash_size
      Size of (number of slots in) the inode hash chain	table for the inode
      least recently used (LRU)	cache.

      Default value: 2048 (slots)

      Minimum value: 64

      Maximum value:  16,384

      Large inode hash chain tables spread the inode structures	and may	make
      chain lengths short.  This can reduce linear searches and	improve
      lookup speeds.  In general, chains should	contain	only 2 or 3 elements.



  nmount
      Obsolete.	 This attribute	has been replaced by the vfs subsystem's
      max_ufs_mounts attribute,	which is tunable at run	time. See
      sys_attrs_vfs(5) for information about max_ufs_mounts.



  ufs_blkpref_lookbehind
      The range	of blocks behind the current block location through which to
      search for a free	block to allocate for an indirect block	write opera-
      tion (for	all writes other than the first). A value greater than 1
      enables a	look-behind search before writing each indirect	block after
      the first	block write operation.

      Default value: 16	(blocks)

      Minimum value: 1

      Maximum value: 64



  ufs_lockholdmax
      The maximum number of vnodes that	UFS can	process	while flushing dirty
      buffers on the mount list	before releasing the lock on the mount list
      to other components.  If ufs_lockholdmax number of vnodes	is reached
      before all dirty buffers on all vnodes are flushed from the mount	list,
      UFS releases the mount list lock and regains it later to process (flush
      dirty buffers on)	the remaining vnodes.

      Default value: 500 (vnodes)

      Minimum value: 0 (means that UFS must release the	mount list lock	each
      time a vnode is processed)

      Maximum value: 5000

      Reducing the value of ufs_lockholdmax can	improve	system responsiveness
      for systems under	heavy I/O load.	The cost is an increase	in CPU over-
      head (more time required to flush	dirty buffers from the mount list).
      Reducing the ufs_lockholdmax value too low or on systems with low	I/O
      overhead incurs CPU cost without increasing system responsiveness.

      If the rt_preempt_opt attribute is set, ufs_lockholdmax is automati-
      cally reduced to 50 to better support the	strict preemption require-
      ments of realtime	operations.



  ufs_object_safety
      A	value that enables (nonzero) or	disables (0) an	operation that res-
      tricts how blocks	of stale UFS data and metadata (such as	inodes)	are
      reused. When ufs_object_safety is	set to a nonzero value,	blocks are
      cleared before being rewritten and update	operations are ordered in a
      certain way to conform to	C2 security requirements. For example, during
      file creation, a dinode is always	written	before a directory entry is
      updated to point to that dinode. When a file is deleted, the directory
      entry is always updated before the dinode	is deleted.

      Default value: 0 (disabled)

      Change ufs_object_safety to a nonzero value only if a C2 security	level
      is a system requirement. There is	a serious UFS performance cost asso-
      ciated with this change. Furthermore, the	default	setting, even though
      not in strict conformance	with C2	security requirements, leaves a	low
      probability that confidential data will be exposed.

SEE ALSO

  sys_attrs(5)