Re: my simh-vax crashed: panic: pmap_enter on PG_SREF page

Den 2023-12-21 kl. 21:37, skrev Kalvis Duckmanton:
> On 22/12/23 01:39, Anders Magnusson wrote:
>> Den 2023-12-21 kl. 03:59, skrev Jason Thorpe:
>>> That patch looks pretty reasonable, but wouldn’t it be better to invalidate the outgoing range?  Generally, best practice is to invalidate a TLB thing when it becomes invalid, rather than when it get a new value.
>> This should be in rmspace(), where the previous process mappings are 
>> removed.
>> Together with a check for number of pages affected, so that it wont 
>> be an giant TBIA loop :-)
>
> I ended up revising my change to something that's almost exactly the 
> same as Jason's patch from elsethread, though I also had an additional 
> TBIS in pmap_enter() immediately after the call to rmpage().  Am I 
> right to think that this last one isn't needed since there is a TBIA 
> at the end of pmap_enter()?
>
Yes, that is correct.

IIRC; the TBIA is because TBIS did take quite some time on 11/750 to 
execute, but TBIA was instant, so when there was many TBIS needed I 
replaced them with TBIA instead (doing a page lookup was not especially 
heavy-weight).  If someone feel for verifying this with newer hardware - 
feel free :-)

The same as with the Unibus BDPs; only when having a heavy I/O load it 
was possible to see any performance gain by using it, so I did never 
implement it.  (I did performance checks using 4.3BSD which used BDPs).

-- Ragge