How multiphysical buffers are used
The multiphysical buffer pool is an area of memory that can be
allocated to various tasks associated with moving data between
memory and physical devices:
The value of the NMPBUF kernel parameter controls
the number of 4KB memory
used for scatter-gather, copy request, and transfer buffers.
The number of pages of memory reserved for these buffers is tuned
automatically if NMPBUF is set to 0.
You can check if sufficient memory
has been assigned as described in
``Tuning the number of multiphysical buffers''.
The system dynamically allocates memory to the following data structures
which are used in performing certain I/O operations:
Scatter-gather buffer headers are used to control scatter-gather
requests if the disk hardware supports scatter-gather. If no
headers are available, the requests are sent to the disk
controller one at a time.
Control blocks are used to send raw disk I/O (AIO)
requests including access to
If no control blocks are available, the process is put to sleep.
How the system uses multiphysical buffers to overcome 24-bit addressing limitations
Tuning the number of multiphysical buffers
Reducing disk I/O by increasing the size of the namei cache
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003