autoup
Parameter
- Description
-
Along with
tune_t_flushr
,autoup
controls the amount of memory examined for dirty pages in each invocation and frequency of file system synchronizing operations.The value of
autoup
is also used to control whether a buffer is written out from the free list. Buffers marked with theB_DELWRI
flag (which identifies file content pages that have changed) are written out whenever the buffer has been on the list for longer than autoup seconds. Increasing the value ofautoup
keeps the buffers in memory for a longer time. - Data Type
-
Signed integer
- Default
-
30
- Range
-
1 to MAXINT
- Units
-
Seconds
- Dynamic?
-
No
- Validation
-
If
autoup
is less than or equal to zero, it is reset to 30 and a warning message is displayed. This check is done only at boot time. - Implicit
-
autoup
should be an integer multiple oftune_t_fsflushr
. At a minimum,autoup
should be at least 6 times the value oftune_t_fsflushr
. If not, excessive amounts of memory are scanned each timefsflush
is invoked.The total system pages multiplied by
tune_t_fsflushr
should be greater than or equal toautoup
to cause memory to be checked ifdopageflush
is non-zero. - When to Change
-
Here are several potential situations for changing
autoup
,tune_t_fsflushr
, or both:-
Systems with large amounts of memory – In this case, increasing
autoup
reduces the amount of memory scanned in each invocation offsflush
. -
Systems with minimal memory demand – Increasing both
autoup
andtune_t_fsflushr
reduces the number of scans made.autoup
should be increased also to maintain the current ratio ofautoup
/tune_t_fsflushr
. -
Systems with large numbers of transient files (for example, mail servers or software build systems) – If large numbers of files are created and then deleted,
fsflush
might unnecessarily write data pages for those files to disk.
-
- Commitment Level
-
Unstable