HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)

f
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 sys-
tem 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 lim-
its 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: February 2007 − 1 − Hewlett-Packard Company 173