Back in the days of IPS/ICS dispatching control, wasn't there something that was referred to as the 'wheeler-dealer mechanism' & does it still exist in some form in the WLM code? >From memory: 1. New task gets created and is assigned a time-slice of 1msec, at a priority of 32 (out of 64 - i.e 'half'), then placed on the dispatch queue 2. Task eventually shuffles to the top of the queue and starts running. 3. If the task voluntarily relinquishes control (due to some sort of SVC call, etc) before the time slice expires, then the time slice duration gets doubled and the priority is reduced by 50%. 4. Alternatively, if the time slice expires and the OS unilaterally wrests control from the task, then the time slice duration gets halved and the priority is bumped by 50% 5. Task is once more placed on the dispatch queue 6. etc...
I may have the actions of (3) and (4) round the wrong way. I wouldn't be at all surprised to be told I'm completely wrong. As I say, this is all from a memory and I seem to have so few neurons left these days. Sean On Sun, 20 Oct 2019 at 14:02, Charles Mills <charl...@mcn.org> wrote: > I just looked up "External Interruption" in the Principles. There are at > least 9 possible causes. > > IIRC on the System 360 there was an eight-pin Molex connector available > and a customer-provided box of some sort could trigger an external > interrupt by pulling the appropriate pin to ground. See page 19 of > http://www.bitsavers.org/pdf/ibm/360/systemSummary/GA22-6810-12_360sysSumJan74.pdf > . > > IIRC MICR check sorters used this feature to generate their high-priority > interrupts to the processor. > > Charles > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On > Behalf Of Tom Brennan > Sent: Saturday, October 19, 2019 7:24 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Best way for a task to give up the CPU and let other tasks > run? > > Interesting, thanks! So it generates an external interrupt. I always > thought that one was only for the external interrupt "key", but this > page indicates CPU timer and some kind of CP-to-CP communication too: > > > https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconc_interrupts.htm > > Ok... now back to my weekend work, like changing the oil in my truck. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
