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Revision 1.3 / (download) - annotate - [select for diffs], Thu Nov 10 23:57:31 2022 UTC (18 months, 3 weeks ago) by jsg
Branch: MAIN
CVS Tags: OPENBSD_7_5_BASE,
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Revision 1.2 / (download) - annotate - [select for diffs], Sat Nov 5 23:18:03 2022 UTC (19 months ago) by jmc
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- escape a macro in an Rs/Re block: groff appears to think it is callable - while here, sort NAME
Revision 1.1 / (download) - annotate - [select for diffs], Sat Nov 5 19:29:45 2022 UTC (19 months ago) by cheloha
Branch: MAIN
clockintr(9): initial commit clockintr(9) is a machine-independent clock interrupt scheduler. It emulates most of what the machine-dependent clock interrupt code is doing on every platform. Every CPU has a work schedule based on the system uptime clock. For now, every CPU has a hardclock(9) and a statclock(). If schedhz is set, every CPU has a schedclock(), too. This commit only contains the MI pieces. All code is conditionally compiled with __HAVE_CLOCKINTR. This commit changes no behavior yet. At a high level, clockintr(9) is configured and used as follows: 1. During boot, the primary CPU calls clockintr_init(9). Global state is initialized. 2. Primary CPU calls clockintr_cpu_init(9). Local, per-CPU state is initialized. An "intrclock" struct may be installed, too. 3. Secondary CPUs call clockintr_cpu_init(9) to initialize their local state. 4. All CPUs repeatedly call clockintr_dispatch(9) from the MD clock interrupt handler. The CPUs complete work and rearm their local interrupt clock, if any, during the dispatch. 5. Repeat step (4) until the system shuts down, suspends, or hibernates. 6. During resume, the primary CPU calls inittodr(9) and advances the system uptime. 7. Go to step (2). This time around, clockintr_cpu_init(9) also advances the work schedule on the calling CPU to skip events that expired during suspend. This prevents a "thundering herd" of useless work during the first clock interrupt. In the long term, we need an MI clock interrupt scheduler in order to (1) provide control over the clock interrupt to MI subsystems like timeout(9) and dt(4) to improve their accuracy, (2) provide drivers like acpicpu(4) a means for slowing or stopping the clock interrupt on idle CPUs to conserve power, and (3) reduce the amount of duplicated code in the MD clock interrupt code. Before we can do any of that, though, we need to switch every platform over to using clockintr(9) and do some cleanup. Prompted by "the vmm(4) time bug," among other problems, and a discussion at a2k19 on the subject. Lots of design input from kettenis@. Early versions reviewed by kettenis@ and mlarkin@. Platform-specific help and testing from kettenis@, gkoehler@, mlarkin@, miod@, aoyama@, visa@, and dv@. Babysitting and spiritual guidance from mlarkin@ and kettenis@. Link: https://marc.info/?l=openbsd-tech&m=166697497302283&w=2 ok kettenis@ mlarkin@