fcache_async_cache_invalidate.5 (2012 03)

f
fcache_async_cache_invalidate(5) fcache_async_cache_invalidate(5)
(Tunable Kernel Parameters)
NAME
fcache_async_cache_invalidate - toggle the deferred freeing of cached pages
VALUES
Failsafe
1
Default
1
Allowed values
0-1
Recommended Values
Default value
DESCRIPTION
The
fcache_async_cache_invalidate
tunable is used to toggle the deferred freeing of cached
pages. By default, this tunable is set to 1; in other words. it is turned ON, and the freeing of cached
pages is deferred.
When this tunable is set to a value of 1, the system will try to asynchronously free pages from the cache
that are in use by files that are being removed via the rm(1) command, or those pages that are in cache
that are being used by the file systems and are being released via the umount (1) command.
When this tunable is set to a value of 0, the system will free such pages from the cache synchronously.
Who Is Expected to Change This Tunable?
Administrators investigating the performance characteristics of file I/O intensive workloads.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Value of This Tunable be changed?
Leaving this tunable at its default value of 1 improves performance in work loads where large amounts of
files are being removed regularly, or in cases where file systems are being unmounted. However, setting
this value to 1 leaves the free pages in such a state as to cause them to exist as smaller contiguous
chunks.
Applications starting up after an rm(1) or a umount (1) operation may use up smaller translations and
incur a higher TLB miss penalty, especially if the pages just released represent a sizable portion of the
free memory in the system.
Change this tunable value to 0 only if there appears to be an adverse impact on application startup times,
and if performance in paths where pages are being freed back to the system are not of much concern.
What Other Tunable Values Should Be Changed at the Same Time?
None
ERRORS
[EINVAL] An invalid value is entered that is not an integer and is not 0 or 1, such as a negative
number.
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://www.hp.com/go/hpux-core-docs.
HP-UX 11i Version 3: March 2012 − 1 − Hewlett-Packard Company 1