1 04/01/86  tune_disk
 2 
 3 Syntax as a command:  tune_disk DRIVE_NAME IO_TYPE -load N -response N
 4                  or:  tune_disk reset_max
 5                  or:  tune_disk reset_sys
 6                  or:  tune_disk stagnate N
 7                  or:  tune_disk system IO_TYPE {-max n} {-map IO_TYPE}
 8 
 9 
10 Function: alters disk tuning parameters.  A description of disk tuning
11 techniques can be found in the Multics System Maintenance Procedures
12 manual (AM81).
13 
14 
15 Arguments:
16 DRIVE_NAME
17    is the name of the disk drive to be tuned; for example, dska_05.
18 IO_TYPE
19    identifies one of the I/O types tunable by tune_disk, where IO_TYPE
20    can be one of the following:
21       page_read
22       page_write
23       vtoce_read
24       vtoce_write
25       test_read
26       test_write
27 
28 
29 reset_max
30    requests that all queue maximum depth meters be reset in the
31    disk_seg data base.  The time and date at which the meters were last
32    reset is also maintained in the data base.  This argument is useful
33    to permit a new/lower max depth to be seen after altering tuning
34    parameters or after an allocation lock has occurred.
35 reset_sys
36    requests that all system depth counters be reset to 0.  This is
37    useful after altering system depth counter mapping.  If counter
38    mapping has been changed while requests were in the queue, the
39    counter that had been used may be left artificially high.  Resetting
40    back to 0 lets the system correct the value.
41 
42 
43 stagnate N
44    specifies a change of the system-wide stagnation time period to the
45    specified number of seconds.  (Maximum stagnation time period: 6)
46 system
47    indicates modification of a system-wide optimization factor.  The
48    maximum depth and/or mapping for the specified io_type will be
49    altered.  If neither a maximum depth value nor a mapping is altered,
50    an error message is issued.
51 
52 
53 
54 Control arguments:
55 -load N, -ld N
56    defines the optimization maximum queue loadpoint for the specified
57    drive.  The value N is stated in terms of queue elements.  For
58    blocking I/O, this value would typically reflect a point that
59    preserves sufficient multiprogramming.  For nonblocking I/O, this
60    would typically reflect a point before resource saturation would
61    occur and cause the I/O type to become blocking.  The -load value is
62    one of the two points (along with -response) that define the
63    optimization line.  If you specify -load 1, the initial response
64    value is the optimizing multiplier and no load optimization is
65    performed.
66 
67 
68 -map IO_TYPE
69    specifies that the current depth counting for the specified
70    system-wide optimization entry should be done using the counter for
71    io_type.  For example,
72       tune_disk system PageRead -map PageWrite
73    would have the depth counter for PageWrite used to accumulate the
74    number of PageRead IO's currently outstanding.
75 -max N
76    indicates that the maximum depth for the specified system-wide
77    optimization entry should be set to N.  If this depth is reached,
78    then full optimization of this I/O type will be done system wide for
79    all drives.
80 -response N, -rsp N
81    defines the optimization maximum response value.  This value is the
82    multiplier to be used for an IO_TYPE queue load of a single request.
83 
84 
85 Access required: This command requires access to the hphcs_ gate.
86 
87 
88 Notes:  Refer to the Multics System Maintenance Procedures manual,
89 (AM81) for a description of disk tuning techniques.