[Simh] some performance issues

[Pontus Pihlgren]

Hi

I'm having trouble understanding your question. Are 
you comparing CPU-time of a real VAX(which model?) to 
emulated CPU-time on an Itanium machine(which one?).

Emulation will have an associated overhead. If you 
are compareing a fast VAX to an emulation on a slow 
Itanium... well, Itanium is hard to optimize for.

/P

On Tue, Mar 05, 2019 at 03:13:53PM +0100, gérard Calliet wrote:
> Hello,
> 
> Again I have some performance issues with simh.
> 
> I built it  on OpenVMS Itanium. It runs on a process with enought
> memory, it takes 1 of the 8 CPU Itanium with 100%, no page faults,
> and 100 BIO by second.
> 
> On the emulated VAX we are running processes CPU intensive (old Ada
> compiler), they take 100% of the CPU, also very few page fault, very
> few IO.
> 
> And the CPU time is about 2 or 3 times the CPU time on the hardware,
> and so elapsed time 3 or 4 times. (For my understanding, it is
> difficult to think the same stream of instructions can use different
> CPU times between hardware and SIMH).
> 
> Where can I do something to improve performance? Are there
> parameters (or constant in compilation) in SIMH which could help?
> And the specific context is processes doing almost only CPU
> computing.
> 
> 
> >>>> my configuration, and what commit I use
> on error continue
> load -r ka655x.bin
> attach NVR ka655.nvr
> set cpu 512m
> set cpu conhalt
> set RL disable
> set LPT disable
> set TQ disable
> set -L rq0 rauser=18000000
> attach rq0 datauser2.dsk
> set xq mac=08-00-2B-3C-96-75
> attach xq eth0
> dep bdr 0
> b cpu
> 
> 
> $ run vax-i64
> MicroVAX 3900 simulator V4.0-0 Beta        git commit id: 8810571d
> sim>
> 
> 
> >>>>>>>>>>>>>>
> 
> Thanks,
> 
> Gérard Calliet
> 
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