Programmer 7500/MAX_PROGRAMMERS.iso/PROGRAMS/UTILS/DOS_HELP/DISKBUF2.ZIP/DISKBUF.DOC

Text File | 1989-11-02 | 18.3 KB | 428 lines

                                     DISKBUF

                   A Program to Optimize the BUFFERS= Setting
                                 Version 2.00(2)

                                       by

                                  W. G. Madison


                               Copyright 1987, '89
                        W.G. Madison and Associates, Ltd.
                              All rights reserved.


                                November 1, 1989


        NOTICE: The program DiskBuf and this associated documentation are
        copyrighted products. They may be freely distributed, provided
        only that both the program and documentation are distributed
        together, that no modification is made to either the program or
        the documentation, and that no charge other than a copying charge
        not to exceed $6.00 is levied on the recipient. Disk distributors
        may include promotional text with this program, provided that
        such text appears as a separate file or as text appended to this
        documentation. If appended to this document, such text must be
        readily identifiable as to its source and must appear ONLY at the
        end of the document file. Finally, neither the author nor MADISON
        AND ASSOCIATES assume any responsibility or liability for actual
        or consequential damages arising from the use of this program,
        even if they have been notified in advance of the possibility of
        occurrence of such damages.

        We would like to know of your experience with DiskBuf. Please
        address any criticisms or comments to:

                        W.G. Madison and Associates, Ltd.
                        Consultants / Information Systems
                                  P. O. Box 898
                               Greenbelt, MD 20770
                                  [phone]
                             (CompuServe  73240,342)


                * * * * * * * * * * * * * * * * * * * * * * * * *


        Acknowledgment: Release 1 of this program was based upon ideas
        gleaned from the public domain program THRASHER, by Monte Fergu-
        son of Ravenna, OH. This release, 2.00(2), has been enhanced as a
        result of several user suggestions received over the intervening
        two years. My thanks to all who have contributed.




                                   1



        Disclaimer: This program is provided AS IS, with no claim for
        suitability for any particular purpose. Specifically, since the
        program is necessarily extremely disk intensive and therefore
        exercises the head positioning mechanism far more than is custom-
        ary in normal use, the Author and W. G. Madison and Associates,
        Ltd. disclaim any and all responsibility for actual and/or con-
        sequential damages to hardware and/or files resulting from the
        use of this program.


        INTRODUCTION:

             All personal computers using the DOS operating system (PC-
        DOS, MS-DOS, etc.) use buffered I/O when reading from or writing
        to the disk, unless the programmer who wrote the software being
        used went to great lengths to avoid it. The number of buffers
        used is specified in the file CONFIG.SYS, which is read at the
        time the computer is booted up.

             If you are not familiar with the CONFIG.SYS file or with the
        concept of buffered I/O, it is strongly suggested that you refer
        to your DOS reference manual before proceeding further.

             The problem of determining the proper number of buffers with
        which to configure a DOS computer is, at best, inadequately add-
        ressed in most DOS reference manuals. Generally, the suggested
        approach is "Try a number, then use your computer, then try
        another number. Keep repeating this process until you are either
        fed up or have arrived at something which gives acceptable per-
        formance." Some reference manuals give a suggested value to be
        used by those looking for an easy out. This suggested value may
        or may not yield performance which is close to optimum.

             DiskBuf provides a method for scanning through an entire
        range of values while you go out for coffee (or something
        stronger).


        WHY WORRY ABOUT THE NUMBER OF BUFFERS?

             As might be expected, buffering uses RAM. Specifically, each
        buffer added to a DOS system uses 33 paragraphs (528 bytes) of
        RAM. Assuming that plenty of RAM is available, it might be tempt-
        ing to take the approach, "Let's just set the number of buffers
        way up, and fly with that." Unfortunately, one can reach the
        point where more time is spent searching buffers for information
        than is necessary or desirable. A point of diminishing returns is
        reached.

             Similarly, too few buffers will cause the computer to go to
        the disk more often than necessary. And, since disk operations
        are dreadfully slow in comparison to memory operations, unaccept-
        able performance degradation will result.




                                   2



        WHY USE THE DISKBUF PROGRAM TO SOLVE THE PROBLEM?

             Basically, without an intimate knowledge of the insides of
        DOS plus a penchant for solving complex mathematical problems,
        there are three feasible methods for attacking the problem. The
        first is to pick a number (based either upon your liking for
        indulging in Russian roulette, or upon recommendations from
        friends or the DOS reference manual) and put your trust in the
        tooth fairy as to the appropriateness of the number. The second
        is to try to determine the number by systematic trial and error,
        editing your CONFIG.SYS file over a period of time. The third
        method is to set up an automatic process which can sweep through
        a series of values, perform a realistic test with each value, and
        record the results for later analysis.

             The DISKBUF program permits this third approach to be taken
        easily. By using DISKBUF, you can readily determine the optimum
        number of buffers to be used, based not only upon time to perform
        the test but also upon the amount of RAM occupied by the buffers.
        You can decide, and have some rational basis for the decision,
        whether you are willing to sacrifice X bytes of additional RAM in
        order to gain an additional Y% performance improvement from your
        disk operations.

             Sure beats flying by the seat of the pants, no?



        HOW DO I USE DISKBUF?

             Seven files are included in the file DISKBUF.ZIP. They are,
        respectively:

                  DISKBUF.DOC    (This file)
                  DISKBUF.EXE    (The operational program)
                  AUTOEXEC.BAT   (A specimen AUTOEXEC file)
                  BUFTST-1.EXE   (One of the two provided test modules.
                                 This is the test you would probably want
                                 to use if your typical activity involved
                                 accessing many files scattered over the
                                 disk.)
                  BUFTST-2.EXE   (The second of the two provided test
                                 modules. This is the test you would
                                 probably want to use if your typical
                                 activity involved random accessing of a
                                 relatively few large files.)
                  BUFFTEST.EXE   (A copy of BUFTST-1.EXE. This copy is
                                 the one which will actually be used in
                                 testing.)
                  PLOTBUF.COM    (The program to produce a screen plot of
                                 the test results. Assumes a CGA card.)

             Examine the AUTOEXEC.BAT file. You will see, as the last
        line of the file, the line invoking DISKBUF. In the REMark lines
        preceding this, you will see guidelines for setting the switch


                                   3



        values to be passed to DISKBUF. The switches are:

                            /TARGET=     (Sets the disk to be tested)
                            /MAXBUF=     (Sets the stopping point (maxi-
                                         mum number of buffers) for the
                                         test)
                            /MINBUF=     (Sets the starting point (mini-
                                         mum number of buffers) for the
                                         test)
                            /PLOT        (If present, a screen plot of
                                         the test results will be pro-
                                         duced)

             The first two switches, /TARGET= and /MAXBUF= are required;
        the other two, /MINBUF= and /PLOT are optional.

             /TARGET=xx     takes as an argument a valid disk device
        designator, with the appended colon being optional. This deter-
        mines the device or partition which is to be tested. (Required)

             /MAXBUF=nn     takes as an argument an integer between 1 and
        99, and determines the greatest number of buffers to be used in
        the test. (Required)

             /MINBUF=nn     also takes as an argument an integer between
        1 and 99, and determines the starting number of buffers to be
        used in the test. If this switch is omitted, a starting value of
        3 will be used. (Optional)

             /PLOT          determines by its presence or absence whether
        or not a screen plot of the test results will be produced at the
        completion of the test. NOTE: If your computer does not have a
        graphics card, this switch must not be included! (Optional)


             To use DISKBUF, the following steps are required.

             STEP 1.   Format a floppy disk using the /S switch to make
        the disk bootable.

             STEP 2.   Edit the AUTOEXEC.BAT file provided with the
        DISKBUF distribution set, to invoke DISKBUF with the switch set-
        tings you want used.

             STEP 3.   Copy the edited AUTOEXEC.BAT file and the program
        file DISKBUF.COM onto the disk prepared at Step 1.

             STEP 4.   Copy your own CONFIG.SYS file onto the disk
        prepared at Step 1. If necessary, edit the CONFIG.SYS to make
        sure that the BUFFERS= parameter is ***OUTSIDE*** the range
        determined by the MAXBUF= and MINBUF= parameters in the
        AUTOEXEC.BAT file. (For that matter, if you simply delete the
        BUFFERS= line from the CONFIG.SYS file, DISKBUF will manage it
        appropriately.)



                                   4



             STEP 5.   Copy any device drivers to be installed by the
        CONFIG.SYS over to the floppy. Do the same for any resident
        programs to be installed by the AUTOEXEC.BAT.

             STEP 6.   Copy DISKBUF.EXE to the floppy. If /PLOT is
        selected in the AUTOEXEC.BAT, copy PLOTBUF.EXE to the floppy.

             STEP 7.   Decide, based on the descriptions given above,
        which of the two test modules you wish to use. Copy the desired
        module to the floppy as BUFFTEST.EXE using the DOS COPY command.
        (For the average user, we believe that BUFTST-1.EXE more nearly
        reflects typical usage; it is therefore the one already set up.)

             STEP 8.   Re-boot your computer.

             STEP 9.   Go to lunch, and come back in an hour or so.
        (Optional)


             When the test is completed, two new files will be on the
        floppy disk:

                       BUFFERS.RPT contains the test results, giving for
                                   each number of buffers tested a figure
                                   of merit and the minimum requirement
                                   of RAM (in bytes) for DOS.
                       BUFFERS.PLT contains information used by the pro-
                                   gram PLOTBUF.COM. Specifically, each
                                   line contains the number of buffers
                                   tested and the figure of merit.


             The figure of merit for a given number of buffers is propor-
        tional to the time required for the test. Thus, SMALLER is
        BETTER. The minimum figure of merit is the one you want (ignoring
        the amount of space occupied by the buffers).

             Note that, if /PLOT was selected, the screen plot only dis-
        plays a limited range of the figure of merit values. Specific-
        ally, the range displayed is from the minimum figure of merit to
        5% greater than this value. All figures of merit greater than
        this are clipped at this level for plotting purposes. This was
        done in order to better present the detail of the values only
        slightly worse than the minimum value.

             The screen plot may be recreated at any time by running
        PLOTBUF. The only restriction is that the file BUFFERS.PLT must
        be in the current disk and directory.

             Should you wish to test against two different disks, the
        files BUFFERS.* must be copied or renamed before the second test
        is conducted. If this is not done, the files will be over-written
        and the results of the earlier test will therefore be lost.




                                   5



             Should you wish to re-test the disk using the other provided
        test, simply return to Step 7 above and proceed from there. It
        will not be necessary to edit the CONFIG.SYS file, since (unless
        you are also increasing the MAXBUF= setting in the AUTOEXEC.BAT
        file) the BUFFERS= setting is guaranteed to be outside the
        testing range.


        HOW CAN I DESIGN MY OWN TEST MODULES?

             Two fundamentally different test modules are provided which
        represent quite different testing scenarios.

             BUFTST-1.EXE examines the directory entry for each file in
        every directory on the disk being tested. Thus, it simulates a
        situation in which the user is accessing many files in any given
        session.

             BUFTST-2.EXE writes a single large (1000 record, 100 bytes
        per record) file in the root directory of the target disk. It
        then interchanges record 1 with record 1000, record 2 with record
        999, etc. Having completed this sub-test, it then interchanges
        record 1 with record 2, record 2 with record 3, ... record 999
        with record 1000. Thus, it simulates both sequential and random
        usage of large files.

             You are free to generate your own tests as you will. These
        tests can be implemented in either executable (.EXE or .COM)
        files, or in batch control (.BAT) files. In either case, the file
        name **must** be BUFFTEST (i.e., BUFFTEST.COM, BUFFTEST.EXE, or
        BUFFTEST.BAT). The test module must expect a single command line
        parameter of the form <d>:\ where <d> is the drive letter of the
        drive to be tested.

             One word of caution. It is important that the operations
        being performed be exactly duplicated from run to run, if the
        output data are to accurately reflect your system behavior. Thus
        if you have, e.g., put together a batch file (BUFFTEST.BAT) which
        performs a MAKE, it is important that you recognize ahead of time
        just which files will be created as a result of the MAKE, and
        delete them prior to terminating your BUFFTEST.BAT.


        HOW DOES DISKBUF DO ALL THAT GOOD STUFF?

             When DISKBUF is invoked, it performs the following
        steps:

             STEP 0.   Read and parse command tail. Set operating par-
             ameters, based on the contents of the command tail.

             STEP 1.   Edit the file CONFIG.SYS on the floppy disk.





                                   6



                  STEP 1A.   If the BUFFERS= line is present, read it to
                  extract the current BUFFERS=  setting.


                       STEP 1A1. If this setting is not between MINBUF
                       and MAXBUF then re-write CONFIG.SYS with a
                       BUFFERS=  setting equal to the value of MINBUF,
                       and go to STEP 1C.

                       STEP 1A2. If the setting is between MINBUF and
                       MAXBUF then go to STEP 2.

                  STEP 1B.  If not present, append a BUFFERS= statement
                  with a BUFFERS= setting equal to the value of MINBUF.

                  STEP 1C.  Delete the BUFFERS.* files if they are pres-
                  ent, and re-boot the system.

             STEP 2.   Start the timer.

             STEP 3.   Perform the selected test.

             STEP 4.   Stop the timer.

             STEP 5.   Calculate the figure of merit, and append a record
             to BUFFERS.RPT.  Also append a record to BUFFERS.PLT.

             STEP 6.   Check the current setting of BUFFERS= against the
             value of MAXBUF.

                  STEP 6A.  If buffer setting < MAXBUF, re-edit the
                  existing CONFIG.SYS file, incrementing the buffer set-
                  ting and re-boot the system.

                  STEP 6B.  Otherwise, the test is completed.

                       STEP 6B1. Leave the CONFIG.SYS file on the floppy
                       disk with a BUFFERS= setting at MAXBUF + 1.

                       STEP 6B2. If /PLOT is selected, plot the test
                       results.

                       STEP 6B3. Exit to DOS.














                                   7