Changes between Version 4 and Version 5 of Ticket #228


Ignore:
Timestamp:
06/22/2021 12:50:06 PM (5 years ago)
Author:
Gary Dixon
Comment:

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  • Ticket #228 – Description

    v4 v5  
    22GHM was running in a 2-CPU Multics configuration with a near R2.0 version of the dps8 simulator.
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    4 The Multics process scheduler (pxss.alm) maintains a "bank account" of quantum credits that it doles out to work classes containing a ready-to-run process in the work class queue.  These credits are refreshed on a per-CPU basis each time the scheduler is invoked on that CPU.  The pxss label "compute_virtual_clocks" is preceded by a comment suggesting its purpose is to split idle CPU time among the various categories of idle.  However, one of its initial functions is to measure the number of microseconds that have elapsed since pxss last ran on this CPU, and to add those microseconds (which it calls delta_t) to the tc_data|governing_credit_bank: a one-word data field manipulated as a signed fixed bin(35) integer by the referencing instructions. 
     4The Multics process scheduler (pxss.alm) maintains a "bank account" of quantum credits that it doles out to work classes containing at least one ready-to-run process in its work class queue.  These credits are refreshed on a per-CPU basis each time the scheduler is invoked on that CPU.  The pxss label "compute_virtual_clocks" is preceded by a comment suggesting its purpose is to split idle CPU time among the various categories of idle.  However, one of its initial functions is to measure the number of microseconds that have elapsed since pxss last ran on this CPU, and to add those microseconds (which it calls delta_t) to the tc_data|governing_credit_bank: a one-word data field manipulated as a signed fixed bin(35) integer by the referencing instructions. 
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    66The ALM listing for the code in question is shown below.