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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:  1,073,741,824

      Large inode hash chain tables spread the inode structures and may make
      chain lengths short. In general, chains should contain only 2 or 3
      elements.	 This can reduce linear searches and improve lookup speeds.
      Therefore, ncreasing the value of inode_hash_size can improve
      performance but requires more memory; values closer to the maximum are
      recommended only for Very Large Memory (VLM) systems.

  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	 This attribute has been replaced by the vfs subsystem's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
      operation (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
      overhead (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
      automatically reduced to 50 to better support the strict preemption
      requirements of realtime operations.

  ufs_object_safety
      A value that enables (nonzero) or disables (0) an operation that
      restricts 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
      associated 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)

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