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filecache_max.5 (2010 09)

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filecache_max(5) filecache_max(5)
(Tunable Kernel Parameters)
NAME
filecache_max, filecache_min - maximum or minimum amount of physical memory used for caching file
I/O data
VALUES
Failsafe
filecache_min
: approximately
5% of physical memory
filecache_max
: approximately
5% of physical memory
Default
filecache_min
: approximately
5% of physical memory
filecache_max
: approximately
50% of physical memory
The defaults are computed and adjusted automatically, based on the amount physical memory on the sys-
tem.
The current default value, when displayed by
kctune
, will be expressed as the current value used inter-
nally by the system (representing bytes). The displayed value will vary as the internal value is automati-
cally adjusted.
Allowed values
Minimum
filecache_min: not less than the equivalent of 1 megabyte
Minimum
filecache_max: not less than the equivalent of 1 megabyte
Maximum
filecache_min: not greater than the equivalent of 70% of physical memory
Maximum
filecache_max: not greater than the equivalent of 90% of physical memory
See
Restrictions on Changing below.
Values can be specified as:
1) Default
2) A percentage of total physical memory:
A positive whole number followed by a percent symbol (for example, 70%).
3) A constant value:
A positive whole number that represents number of bytes of physical memory, optionally fol-
lowed by a multiplier suffix, where
K=1000, KB=1024, M
=1000000, MB=(1024*1024), and
GB=(1024*1024*1024)
.
Recommended values
It is recommended that these tunables are left in the automatic (default) state, to allow the system to
better balance the memory usage among filesystem I/O-intensive processes and other types of processes.
DESCRIPTION
These tunables control the amount of physical memory that can be used for caching file data during file
system I/O operations.
The amount of physical memory that is specified by the
filecache_min tunable is reserved and
guaranteed to be available for file caching.
The amount of physical memory used for file caching can grow beyond
filecache_min,upto
filecache_max, depending on I/O load and competing requests for physical memory.
When these tunables are set to default, or set to a percent value, they automatically adjust with Online
Addition or Deletion (OL*) of physical memory, as appropriate.
Who Is Expected to Change These Tunables?
The automatic (default) state should be appropriate for most environments.
You must set these tunables to a constant value (not default or percent) if you want to specify file cache
limits with finer granularity than percent of physical memory (for example, a minimum size or fixed size
of <1% of physical memory).
You must set these tunables to a constant value (not default or percent) if you do not want the limits of
the file cache to adjust with OL* of physical memory.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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