bufpages
bufpages defines the number of 4096-byte memory pages in
the file-system buffer cache.
0 or 6 (Nbuf*2 or 64 pages)
0
Specify integer value or use integer formula expression. Use non-zero value only if dynamic buffer cache is not being used. For more information, see Specifying Parameter Values.
bufpages specifies how many 4096-byte memory pages are
allocated for the file system buffer cache. These buffers are used for
all file system I/O operations, as well as all other block I/O
operations in the system (exec, mount, inode
reading, and some device drivers.)
bufpages
To enable dynamic buffer cache allocation, set bufpages to
zero. Otherwise, set bufpages to the desired number of
4-Kbyte pages to be allocated for buffer cache. If the value specified
for bufpages is non-zero but less than 64, the number is
increased at boot time and a message is printed, announcing the change.
If bufpages is larger than the maximum supported by the
system, the number is decreased at boot time and a message is
printed.
bufpages interacts with
nbuf as follows:
bufpages = 0, nbuf = 0: Enables
dynamic buffer cache.
bufpages not zero, nbuf = zero:
Creates bufpages/2 buffer headers and allocates
(bufpages times 4 Kbytes) of buffer pool space at
system boot time.
bufpages = 0, nbuf not zero: Allocates
nbuf*2 pages of buffer pool space and creates
nbuf headers at boot time.
bufpages not 0, nbuf not zero:
Allocates bufpages pages of buffer pool space and
creates nbuf buffer headers at boot time. If the
two values conflict such that it is impossible to configure a
system using both of them, bufpages takes
precedence.
bufpages controls how much actual memory is allocated to
the buffer pool. See nbuf
.
If bufpages is zero at system boot time, the system
allocates two pages for every buffer header defined by
nbuf. If bufpages and nbuf are
both zero, the system enables dynamic buffer cache allocation and
allocates a percentage of available memory not less than dbc_min_pct nor more
than dbc_max_pct ,
depending on system needs at any given time.
The maximum amount of memory that can be allocated to the buffer pool is also affected by the amount of memory allocated to the system for other purposes. Thus, modifying parameters that affect system memory may also affect the maximum amount of memory can be made available to the buffer pool.