HP-UX Reference (11i v2 07/12) - 5 Miscellaneous (vol 9)

m
memfs_bufcache_metapct(5) memfs_bufcache_metapct(5)
(Tunable Kernel Parameters)
NAME
memfs_bufcache_metapct - maximum percentage of buffer cache which can accommodate MemFS metadata
VALUES
Failsafe
10
Default
10
Allowed values
Integral values: 10 - 50
DESCRIPTION
The metadata of all the MemFS filesystems configured in the system is stored in the buffer cache. The
memfs_bufcache_metapct
tunable defines the maximum percentage of buffer cache which can
accommodate MemFS metadata. Metadata buffers of a MemFS filesystem are never swapped out of the
buffer cache or reused, unless the MemFS filesystem is unmounted.
Restrictions on Changing
The tunable should not be kept at a very high value as it may impact the performance of applications that
use the buffer cache. The tunable is dynamic.
When Should the Value of This Tunable Be Raised?
The value of
memfs_bufcache_metapct
may need to be raised on systems where there are a large
number of files and directories in MemFS filesystems.
What Are the Side Effects of Raising the Value?
The performance of applications that perform I/O on filesystems that use the buffer cache, other than
MemFS, might get reduced.
When Should the Value of This Tunable Be Lowered?
The value of
memfs_bufcache_metapct
can be lowered on systems with small or no mounted MemFS
filesystems.
What Are the Side Effects of Lowering the Value?
This limits the number of files and directories that can be created in MemFS filesystems.
What Other Tunable Values Should Be Changed at the Same Time?
None.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at
http://docs.hp.com.
AUTHOR
memfs_bufcache_metapct was developed by HP.
SEE ALSO
kctune(1M), mount_memfs(1M), sam(1M), gettune(2), settune(2).
HP-UX 11i Version 2: December 2007 Update − 1 − Hewlett-Packard Company 243