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sys_attrs_ufs(5)
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sys_attrs_ufs - ufs subsystem attributes
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 performance.
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 memory; values closer to the maximum
are recommended only for Very Large Memory (VLM)
systems.
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 This attribute has been replaced by the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.
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 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.
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.
sys_attrs(5)
sys_attrs_ufs(5)
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