Solaris Tunable Parameters Reference Manual - SCN Research

2. On every invocation, fsflush examines a portion of memory and causes modified
pages to be written to their backing store. Pages are written if they are modified
and if they do not meet one of the following conditions:
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Pages are kernel page
Pages are free
Pages are locked
Pages are associated with a swap device
Pages are currently involved in an I/O operation
The net effect is to flush pages from files that are mapped with mmap with write
permission and that have actually been changed.
Pages are flushed to backing store but left attached to the process using them. This
will simplify page reclamation when the system runs low on memory by avoiding
delay for writing the page to backing store before claiming it, if the page has not
been modified since the flush.
3. fsflush writes file system metadata to disk. This write is done every nth
invocation, where n is computed from various configuration variables. See
“tune_t_fsflushr” on page 40 and “autoup” on page 41 for details.
The following features are configurable:
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Frequency of invocation (tune_t_fsflushr)
Whether memory scanning is executed (dopageflush)
Whether file system data flushing occurs (doiflush)
The frequency with which file system data flushing occurs (autoup)
For most systems, memory scanning and file system metadata synchronizing are the
dominant activities for fsflush. Depending on system usage, memory scanning can
be of little use or consume too much CPU time.
tune_t_fsflushr
Description
Data Type
Default 1
Range
Units
Dynamic?
Specifies the number of seconds between fsflush invocations
Signed integer
1 to MAXINT
Seconds
No
Validation If the value is less than or equal to zero, the value is reset to 1
and a warning message is displayed. This check is done only
at boot time.
40 Solaris Tunable Parameters Reference Manual • June 2005