On Mon, 21 Oct 2019 19:01:15 +0000, Jesse 1 Robinson wrote: >(Now with some actual content.) The standard justification for spin loop is >that the area of code in question is executed *very* frequently and is *very* >short. > I'd say, rather, the typical *wait* is *very* short.
>... In other words, not worth the overhead of an actual WAIT nor the delay in >having to get redispatched afterwards. Spin loop is not an ideal strategy >but--as long as all goes well--worth the improved performance overall. The >biggest problem with spin loop is on a single CP machine when the loop does >not terminate properly. If a second CP is available, it can jump in and >interrupt the loop. With no second CP in the picture, the loop may go on and >on. > Deadlock? The likelihood goes down with the number of CPUs. But that's what dooms the strategy of STIMER and retry (akin to a slow spin) to resolve DSN ENQ. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
