[Simh] performance issues vax / simh / openvms / itanium

[Wilm Boerhout]

Does The compiler generate simh code that causes alignment faults when simh
executies? A notorious source of bad performance on early Itanium ports.

/Wilm
Op ma 24 apr. 2017 om 14:22 schreef gérard Calliet <
gerard.calliet at pia-sofer.fr>

> Hello,
>
> I have a VAX emulated with simh compiled and running on OpenVMS 8.4-1H1
> (vsi) Itanium i4. The software used does only heavy cpu tasks (Ada cross
> compiler).
> The performance is surprinsigly bad: about 4 times lower than then VAX
> station 4000-90. A compilation batch which was taking 7mn of CPU takes
> on the emulator 24mn of CPU.
> The host Itanium uses 1 core at 100%, and not a lot of page faults, 100
> dio /s which I think is for the emulated clock.
>
> (I use the same (back/image) system disk as of the initial hardware VAX.
> I have verified I use all the 512m of memory, there are not a lot of
> page fault on the VAX.)
>
>
> I don't understand why it is so bad. I thought about some special things
> on C compilation, but which?
> Any suggestions?
>
> Thanks,
> Gérard Calliet
>
>
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