nfs:nacache

Description

Tunes the number of hash queues that access the file access cache on the NFS client. The file access cache stores file access rights that users have with respect to files that they are trying to access. The cache itself is dynamically allocated, but the hash queues used to index into it are statically allocated. The algorithm assumes that there is one access cache entry per active file and four of these access cache entries per hash bucket. Thus, by default, the value of this parameter is set to the value of the nrnode parameter.

Data Type

Integer (32–bit)

Default

The default setting of this parameter is 0, which means that the value of nacache should be set to the value of the nrnode parameter.

Range

1 to 2³¹ - 1

Units

Access cache entries

Dynamic?

No. This value can only be changed by adding or changing the parameter in the /etc/system file, and then rebooting system.

Validation

None. However, setting this parameter to a negative value will probably cause the system to try to allocate a very large set of hash queues, and then hang while trying to do so.

When to Change

Examine the value of this parameter if the basic assumption of one access cache entry per file would be violated. This might be true for systems in a time sharing mode where multiple users are accessing the same file at about the same time. In this case, it might be helpful to increase the expected size of the access cache so that the hashed access to the cache stays efficient.

Stability Level

Evolving