TECHNICAL INFORMATION DOCUMENT

TITLE:  TF2013 - add tuneable paging parameters
DATE:  01SEP95
README FOR:  TF2013
PRODUCT and VERSION:

UnixWare 2.01


Installation Instructions:  

DATATYPE: datastream

1.  Download the tf2013 and tf2013.txt files to the /tmp directory
    on your machine.

2.  Read the release notes contained in this file and follow the 
    instuctions to add the package to your system.

3.  Now become root, and add the package to your system using the following 
    commands:

        $ su
        # pkgadd -d /tmp/tf2013

ENGINEERING REALEASE NOTES
--------------------------

Title
-----

PTF2013 - add tuneable paging parameters

Product And Version
--------------------

UnixWare 2.0, UnixWare 2.01

Abstract
--------

PTF2013 provides new modules and other files
for the portion of the kernel that manages paging of system memory.
Several previously hardcoded parameters are now tuneable.

Symptom
--------

Machines with large memory configurations have been observed to hang
when run under stress because existing (previously hardcoded) values 
of certain paging parameters had been chosen for systems of smaller memory.
For large memory systems (e.g. 512 megabytes), the system was not entering 
paging mode sufficiently early; consequently, kernel memory allocations 
began to fail and various applications (e.g., UDP) began to break.

SOLUTION SPECIFICS
------------------

General Description.
-------------------

The six hardcoded values,

        LOTSFREE
        LOTSFREEFRACT
        DESFREE
        DESFREEFRACT
        MINFREE
        MINFREEFRACT

have been removed from the <sys/vmparams.h> header file and
have been replaced by analogous tuneable values in the

        /etc/conf/mtune.d/mem

file with default values corresponding to the previously hardcoded values.


New Features.
------------

The new tuneable parameters are described below
(and in /etc/conf/dtune.d/mem).

The ``paging threshold'' is conrolled by tuneables:

	LOTSFREEBYTES	Absolute paging threshold,
			specified in bytes.

	LOTSFREEFRACT	Relative paging threshold,
			specified as a divisor of total physical memory.

The system initiates paging whenever
the amount of free physical memory is below this threshold.
The ``paging threshold'' is the smaller of
LOTSFREEBYTES and total physical memory divided by LOTSFREEFRACT.


The ``swapping threshold'' is controlled by tuneables:

	DESFREEBYTES	Absolute swapping threshold,
			specified in bytes.

	DESFREEFRACT	Relative swapping threshold,
			specified as a divisor of total physical memory.

The system initiates swapping whenever
the amount of free memory is below this threshold for an extended period.
The ``swapping threshold'' is the smaller of
DESFREEBYTES and total physical memory divided by DESFREEFRACT.


The ``Minimum free memory'' which the system must maintain is controlled by:

	MINFREEBYTES	Absolute minimum free memory,
			specified in bytes.

	MINFREEFRACT	Relative minimum free memory,
			specified as a divisor of the swapping threshold.

The ``minimum free memory'' target is the smaller of
MINFREEBYTES and the swapping threshold (see above) divided by MINFREEFRACT.

Software Notes and Recommendations.
----------------------------------

This PTF can be installed on

	UnixWare 2.0
or	UnixWare 2.01

It needs not be installed on UnixWAre 2.02 (or later)
because this feature is already incorporated in those versions.


Hardware Notes and Recommendations.
----------------------------------

This PTF is targeted for the i386, i486 and Pentium CPU's.

Installation Instructions.
-------------------------

*****	No special instructions ******