Starting with the Solaris 8 6/00 release, the DNLC also caches negative lookup information, which means it caches a name not found in the cache.
4 x (v.v_proc + maxusers) + 320
0 to MAXINT
None. Larger values cause the time it takes to unmount a file system to increase as the cache must be flushed of entries for that file system during the unmount process.
Prior to the Solaris 8 6/00 release, it is difficult to determine whether the cache is too small. It is possible to infer this by noting the number of enters returned by kstat -n ncstats. If the number seems high given the system workload and file access pattern, this may be due to the size of the DNLC.
Starting with the Solaris 8 6/00 release, kstat -n dnlcstats, is available for you to determine when entries have been removed from the DNLC because it was too small. The sum of the pick_heuristic and the pick_last represents otherwise valid entries which were reclaimed because the cache was too small.
Note that excessive values of ncsize have an immediate impact on the system since the system allocates a set of data structures for the DNLC based on the value of ncsize. A system running a 32-bit kernel allocates 36 byte structures for ncsize, while a system running a 64-bit kernel allocates 64 byte structures for ncsize. The value also has a further affect on UFS and NFS unless ufs_inode and nfs:nfs_rnode are explicitly set.
Indicates whether the POSIX semantics for the chown(2) system call are in effect. POSIX semantics are:
A process cannot change the owner of a file unless it is running with UID 0.
A process cannot change the group ownership of a file to a group in which it is not currently a member unless it is running as UID 0.
1, indicating that POSIX semantics are used
0 = POSIX semantics not in force, 1 = POSIX semantics used
When POSIX semantics are not desired. Note that turning off POSIX semantics opens the potential for various security holes. It also opens the possibility of a user changing ownership of a file to another user and being unable to retrieve the file back without intervention from the user or the system administrator.
Specify the amount of kernel pageable memory available. This memory is used primarily for kernel thread stacks. Increasing this number allows either larger stacks for the same number of threads or more threads. This parameter can only be set on systems running 64–bit kernels. Systems running 64-bit kernels use a default stack size of 24 Kbytes.
64–bit kernels, 2 Gbytes
32–bit kernels, 512 Mbytes
64–bit kernels, 512 Mbytes - 24 Gbytes
32-bit kernels, 512 Mbytes
Value is compared to minimum and maximum sizes (512 Mbytes and 24 Gbytes for 64-bit systems) and if smaller than the minimum or larger than the maximum, it is reset to 2 Gbytes and a message to that effect is displayed.
The actual size used in creation of the cache is the lesser of the value specified in segkpsize after the constraints checking and 50% of physical memory.
This is one of the steps necessary to support large numbers of processes on a system. The default size of 2 Gbytes, assuming at least 1 Gbyte of physical memory is present, allows creation of 24–Kbyte stacks for more than 87,000 kernel threads. The size of a stack in a 64-bit kernel is the same whether the process is a 32-bit process or a 64-bit process. If more than this number is needed, segkpsize can be increased assuming sufficient physical memory exists.
For information, see segkpsize (Pre-Solaris 7 and the Solaris 7 Release).
0 (disabled), 1 (enabled)
Yes, but do not change this tunable dynamically. It is possible to enable it if originally disabled, or to disable it if originally enabled. However, enabling, disabling, and then enabling this parameter might lead to stale directory caches.
Directory caching has no known problems, but if problems occur, then set dnlc_dir_enable to 0 to disable caching.
0 to MAXUINT (no maximum)
Yes, it can be changed at any time.
If performance problems occur with caching small directories, then increase dnlc_dir_min_size. Note that individual file systems might have their own range limits for caching directories. For instance, UFS limits directories to a minimum of ufs_min_dir_cache bytes (approximately 1024 entries), assuming 16 bytes per entry.
MAXUINT (no maximum)
0 to MAXUINT
Yes, it can be changed at any time.
If performance problems occur with large directories, then decrease dnlc_dir_max_size.