08/16/84 tune_disk, td Syntax: tune_disk drive_name io_type {-load | -ld} n {-response | -rsp} m tune_disk reset_max tune_disk reset_sys tune_disk stagnate seconds tune_disk system io_type {-max n} {-map io_type} Function: Permits a user with hphcs_ access to alter disk tuning parameters. Arguments: io_type An io_type is the name of a type of IO tunable by tune_disk. If tune_disk is envoked without arguments it will print a usage message which includes the valid io_type names. drive_name Is the name of a disk drive to be tuned. Drive names must begin with the three characters "dsk", followed by a letter, an underline and one or two numeric digits. -load n, -ld n This argument pair defines the optimization maximum queue loadpoint for the specified drive. It is one of the two points which define the optimization line. If -load 1 is specified, the initial response value is the optimizing multiplier and no load optimization is performed. -response m, -rsp m This argument pair defines the optimization maximum response value, which is the multiplier to be used for an IO type queue load of a single request. reset_max This argument requests that all queue maximum depth meters be reset in the disk_seg database. The time and date at which the meters were last reset is also maintained in the database. This argument is useful to permit a new/lower max depth to be seen after altering tuning parameters, or after an Allocation Lock has occurred. reset_sys This argument requests that all system depth counters be reset to 0. This is useful after altering system depth counter mapping. If counter mapping has been changed while requests were in the queue, the counter which had been used may be left artificially high. Resetting back to 0 lets the system correct the value. stagnate seconds This argument pair specifies a change of the system wide stagnation time period to the specified number of seconds. Tune_disk sets a maximum stagnation time period of 6 minutes. system This argument indicates modification of a system-wide optimization factor. The maximum depth and/or mapping for the specified io_type will be altered. If neither a maximum depth value, nor a mapping is altered an error message is issued. -map io_type This argument specifies that the current depth counting for the specified system-wide optimization entry should be done using the counter for io_type. For example: tune_disk system PageRead -map PageWrite Would have the depth counter for PageWrite used to accumulate the number of PageRead IO's currently outstanding. -max n This argument pair indicates that the maximum depth for the specified system-wide optimization entry should be set to n. If this depth is reached then full optimization of this IO type will be done system wide for all drives. Notes: Optimization is performed by determining a multiplier to be used to convert a Phsical Seek Length into a Logical Seek Length, for the purposes of determining the Nearest Logical Seek to perform on a disk drive. The Response Point determines what this multiplier is for a situation with a single request of that IO type in the queue, and is the multiplier required to produce best system response. The Load Point specifies the number of requests permitted in the queue of the specified IO type before full optimization occurs, Logical Seek Length = Physical Seek Length. These two values define the two endpoints of a straight line. The optimization multiplier is determined by the current load of the queue and its corresponding position on the straight line. System-wide queue loading optimization is determined by looking at the system-wide load of an IO type and the maximum depth it should be permitted before becoming fully optimized. The fraction produced by: fraction = max (0.0, (max_depth - depth)/max_depth) is used to alter the individual drive's IO type multiplier to determine the system-wide queue loading effect on individual drive optimization. The system-wide optimization utilizes a max_depth specified for the IO type, and a counter of the current depth to determine the system-wide loading optimization. Depth counters can be mapped together to form an aggregate system-wide queue loading effect. When decrementing, counters are not permitted to become negative, but if re-mapped while non-zero they may remain > 0 with no load. The tuning tools permit resetting the current depth counters for system-wide optimization back to 0, to let the system correct them to a true load indication. All queues have a high-water-mark accumulator. This can be reset through the tuning tools to permit a new high-water-mark to be determined. ----------------------------------------------------------- Historical Background This edition of the Multics software materials and documentation is provided and donated to Massachusetts Institute of Technology by Group BULL including BULL HN Information Systems Inc. as a contribution to computer science knowledge. This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology, Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell BULL Inc., Groupe BULL and BULL HN Information Systems Inc. to the development of this operating system. Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970), renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture for managing computer hardware properly and for executing programs. Many subsequent operating systems incorporated Multics principles. Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. . ----------------------------------------------------------- Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without fee is hereby granted,provided that the below copyright notice and historical background appear in all copies and that both the copyright notice and historical background and this permission notice appear in supporting documentation, and that the names of MIT, HIS, BULL or BULL HN not be used in advertising or publicity pertaining to distribution of the programs without specific prior written permission. Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc. Copyright 2006 by BULL HN Information Systems Inc. Copyright 2006 by Bull SAS All Rights Reserved