[HECnet] Trying to build SIMH from git (on OpenIndiana)

[Cory Smelosky]

On 13 Mar 2013, at 15:04, "Mark Pizzolato - Info Comm" <Mark at infocomm.com> wrote:

On Wednesday, March 13, 2013 at 11:51 AM, Cory Smelosky wrote:
Speaking of SIMH on Solaris and similar...is SIMH capable of SET CPU IDLE in
zones on SPARC?   It looks like 3.9-0 can't.

Well, I think I answered this yesterday on this list.   I'll restate what I wrote here:

Thank you.   I think the answer got lost when my mail server was bouncing all emails. ;)


Idling for any simulator requires that the host system's clock tick be <= the size of the simulated system's clock tick.   VAX systems have a clock tick of 10ms.   Idling for simulated VAX systems works best if the host clock tick is 1ms.

Windows systems have a user mode programmatically settable clock tick size (a facility useful for some media playback capabilities).   On Windows systems simh will set the host's clock tick to 1ms while a simulator is running.   

We haven't seen programmatically settable host clock tick sizes on other platforms.   In general, other platforms have a tick size which can be changed in some system specific way   (which might require building a kernel with a desired tick size) or not changeable at all.     This issue comes up often enough that adding how to make these system specific adjustments would be a useful addition to the simh FAQ.   Any feedback on this subject will be welcome.

Ahhh.

"Solaris timing uses a real-time clock that can generate interrupts at a resolution bound by the processor speed. For scheduling purposes, it fires every 10 milliseconds. As in Linux, this is a clock "tick." Note that 2.6 Linux uses a 1000-tick/second clock, as opposed to the 100-tick/second clock used by Solaris and by previous versions of Linux. User-level programs on Solaris can program the real time clock to fire at nanosecond granularity, rounded up by processor time--much finer than the clock tick granularity of ten or one milliseconds. However, the program interface to use the high-resolution timers is not visible in the DDI/DKI. See  clock_settime(3rt)  for user-level details andusr/src/uts/common/os/cyclic.c  for details on high-resolution timing in Solaris.
Also note that in Solaris, you can change the value of  hz  or clock ticks/second by setting  hires_tick  to 1 and  hires_hz  to the desired time in the  /etc/system  file. The default is 1000 ticks per second. Here's an example:
set hires_tick=1
set hires_hz=10000 <~--- 10000 ticks per second"

Looks like Solaris can set it in user mode, too.


Recent simh code will display what it has determined to be the host's clock size if simh believes the host's clock tick is too small to support idling when you attempt to enable idling. 

Recent simh code can always display host system's tick size with the 'EXAMINE TIMER OS_SLEEP_MIN_MS' command.

The latest simh code is available from https://github.com/simh/simh/archive/master.zip.

Gregg Levine wrote:
Idle on some items that are not Linux or FreeBSD or NetBSD may not 
work because of how they interpret the timer. Same goes for trying to 
get the idle function to work on Windows.

I haven't heard from anyone who's had issues getting idling to work on Windows.   If you know of such a case, I would be interested to explore what may be happening in this case.

Thanks.

- Mark Pizzolato