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

m
memfs_bufcache_swappct(5) memfs_bufcache_swappct(5)
(Tunable Kernel Parameters)
NAME
memfs_bufcache_swappct - percentage of buffer cache at which MemFS data buffers start swapping
VALUES
Failsafe
50
Default
50
Allowed values
Integral values: 0 - 100
DESCRIPTION
The memfs_bufcache_swappct
tunable defines the percentage of the maximum memory that can be
used by buffer cache (specified by
dbc_max_pct ) at which MemFS data buffers begin to get swapped out
from the buffer cache. A lower percentage allows a lesser portion of the buffer cache to be used by MemFS
data buffers and a higher value allows a higher portion of the buffer cache to be used by MemFS data
buffers.
Restrictions on Changing
The tunable should not be kept at a very high value as the performance of applications that use the buffer
cache might be impacted when there is high activity on MemFS filesystems. The tunable is dynamic.
When Should the Value of This Tunable Be Raised?
The value of
memfs_bufcache_swappct
may need to be raised on systems where there are a
significant number of processes that are using MemFS filesystems and for whom performance is important.
What Are the Side Effects of Raising the Value?
The performance of applications that use the buffer cache might get reduced.
When Should the Value of This Tunable Be Lowered?
The value of
memfs_bufcache_swappct
can be lowered on systems where MemFS activity is less or
not needed to be of high performance.
What Are the Side Effects of Lowering the Value?
This might limit the performance of applications that are using the 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_swappct was developed by HP.
SEE ALSO
kctune(1M), mount_memfs(1M), sam(1M), gettune(2), settune(2).
244 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: December 2007 Update