sys_attrs_ufs(5)sys_attrs_ufs(5)NAMEsys_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.
A value that enables (1) or disables (0) the creation of fast
symbolic link files.
Default value: 1 (enabled)
A value that enables (1) or disables (0) the delaying of full
write buffer flushing to disk at the next sync call. Enabling
this attribute might adversely affect real-time workload perfor‐
mance.
Default value: 0 (disabled)
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 mem‐
ory; values closer to the maximum are recommended only for Very
Large Memory (VLM) systems.
Obsolete. This attribute has been replaced by the vfs subsys‐
tem's max_ufs_mounts attribute, which is tunable at run time.
See sys_attrs_vfs(5) for information about max_ufs_mounts.
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
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 respon‐
siveness for systems under heavy I/O load. The cost is an
increase in CPU overhead (more time required to flush dirty buf‐
fers 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 auto‐
matically reduced to 50 to better support the strict preemption
requirements of realtime operations.
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 secu‐
rity 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 secu‐
rity level is a system requirement. There is a serious UFS per‐
formance cost associated with this change. Furthermore, the
default setting, even though not in strict conformance with C2
security requirements, leaves a low probability that confiden‐
tial data will be exposed.
SEE ALSOsys_attrs(5)sys_attrs_ufs(5)