Hi Mark,
I like the idea of splx(splx(7)), but it might be good to make the
level configurable. Currently, the lowest software interrupt used on
NETBSD is level 8 for softclock, but conceivably another system (or a
future version) might have an additional software interrupt level and
make use of 7.
Regarding your last paragraph, there are actually (believe it or not)
still job postings for people with VAX experience. Including various
BSD's, not just VMS.
There is a surprising amount of application software out there that
still runs on vaxes, but the cost of maintaining those machines must
keep increasing. And there is more support available for NETBSD (which
can run 4.3BSD a.out's) via the net or a company similar to Cygnus than
there is for, say, "More/BSD", whose vendor disappeared years ago.
Replacing a Vax running that system with a simulator running NETBSD may
make sense to those with a large investment in applications that run on
their vaxes.
Also, clicking on https://github.com/markpizz/simh/zipball/v3.9-0-rc1
unexpectedly downloaded a file named
"markpizz-simh-v3.8-2-rc2-17-g15570e5.zip".
- michael
On 01/-10/-28163 11:59 AM, Mark Pizzolato - Info Comm wrote:
Hi Chris,
There were issues like this on prior versions of simh. (V3.8-1 and
earlier), which you are running.
The latest (about to be released) version is v3.9-0-rc2 which has
significant improvements to the idle implementation, including a
solution to the issue you found. My earlier comments were
specifically referring to that new idle implementation for the VAX.
The release candidate which is close to release is available at
https://github.com/markpizz/simh/zipball/v3.9-0-rc1
Save what that URL returns as a zip file and unpack it and build a vax
simulator with networking support using:
unzip --a zipfilename.zip
cd markpizz*
make vax
The key issue with recent versions of NetBSD is that earlier versions
of the OS had the vax specific idle routine within an assembler module
called subr.S . The simh idle logic detects the code which is
implemented for idle in subr.S. Meanwhie, newer versions of NetBSD
don't carry this assembler code anymore and a much more complicated
sequence of things going on, essentially all from compiled modules
(from a little examination of the code I've done). The structure of
the idle management has been adjusted to accommodate the features we
have on modern system... (Everything Multi-Core, HyperThreading, etc.)
with some low level tasks delegated to the idle loop as well (page
zeroing). There is one platform specific callout to "cpu_idle().
cpu_idle() is defined in usr/src/sys/arch/vax/include/cpu.h. It is
defined to be a macro: "#define cpu_idle() do {} while
(/*CONSCOND*/0)" A normal compiler wouldn't generate any code for
this macro. If the macro instead was defined to be "#define
cpu_idle() do {splx(splx(7))} while (/*CONSCOND*/0)"
I have sent a message to the NetBSD vax mailing list with the above
suggested change to the base source code. Maybe it will get adopted.
OpenBSD has similar, but different code but I'll make the same
suggestion there as well. Maybe this will end up built into these OS
builds....
I come back to the question of why folks would want to run the new
version of NetBSD on a simulated VAX when they can run a native one
for their host platform which will be the same OS and be more
naturally behaved. If the point is merely to test to see if the OS
still works, that's great, but then you boot it test a few things and
then turn it off. Great idle support isn't needed since it won't be
running continuously.
-Mark
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