> On Dec 11, 2018, at 10:47 AM, Anders Magnusson <ra...@ludd.ltu.se> wrote: > > Den 2018-12-11 kl. 11:11, skrev David Brownlee: >> On Sun, 9 Dec 2018 at 09:42, Mark Pizzolato <m...@infocomm.com> wrote: >>> Well, when I followed the directions you pointed out, I did see what you >>> had reported. A little deeper observation strongly suggested that the >>> OS execution flow that happens on NetBSD/VAX during idling had changed >>> from how things were working when I had worked through how to get things >>> well behaved idling under simh. >>> >>> I haven't yet had the time to look closely at the OS code to determine >>> what exactly was happening. If you're seeing things OK now, maybe, there >>> is some sort of garbage collection activity going on, which runs for a while >>> and then somehow eventually stabilizes to the known idle execution >>> pattern. >>> >>> NetBSD is the fundamental exception for operating systems running under >>> simh due to the fact that it is still an actively developed and evolving >>> operating system. As a result, the idle detection pattern will always have >>> to evolve along with the evolving OS. >> That also cuts both ways (but in a good way :) - because it is still >> under active development it is reasonable to tweak the code to work >> better under simh (other ports like amd64, aarch64 and mips are >> adjusted all the time to work better under qemu), so if there is a >> better way for NetBSD to tag the idle loop, lets make it so :) >> >> For anyone interested the current logic has: >> >> int ipl = mfpr(PR_IPL); >> mtpr(1, PR_IPL); >> mtpr(ipl, PR_IPL); >> >> Which looks to have been there since 2012 - see >> https://nxr.netbsd.org/xref/src/sys/arch/vax/include/cpu.h?r=1.102#162 >> > Hm, the vax actually got a WAIT instruction in later versions of the hardware. > It could be an idea to use it (and add code to catch it if not implemented).
The VAX architecture standard (DEC Std 032, from Bitsavers) mentions that as a virtual machine instruction that's trapped and handled by the hypervisor. It doesn't sound like a real instruction, the way it is on a PDP-11. paul _______________________________________________ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh