/etc/shmcreate, how does it do it?

[Larry Williamson]

In article <403 at uport.UUCP> plocher at uport.UUCP (John Plocher) writes:
>In article <162 at focsys.UUCP> larry at focsys.UUCP (Larry Williamson) writes:
>>
>>I've mailed this same query to Microport hoping to get the answer
>
>	and as soon as I have a chance to look at the source for
>	shmcreate() I'll post the answer (it's just a bit added to
>	the flag argument if memory serves)

Thanks. If this is all that is done, then my troubles will be over.
Or, at least partly over (see next item).


>	The 386 does not have the modified shared memory calls like the 286
>	does.  You need to create a device driver which allows access.
>	If time permits in a few weeks I'll try to post a better answer than
>	this...

This is disheartening. I would like to have used the same (as much as
possible) driver on both systems. Giving the user process direct access
to this physical buffer is important only because of the size of the
buffer and the amount of access that it will receive. There is about
1 Meg of memory involved and the user process will be thrashing it
pretty hard. Having the driver move the entire buffer to the user's
virtual memory adds quite a lot of overhead that I'd rather avoid. 

I'll have to investigate my options here a little better.

>
>>an int. Therefore, only 65535 bytes can be specified! Is this, infact
>>true, or is there something that I've overlooked?
>
>	on the 386, ints are 32 bits (a long int in 286-speak)

Yes, of course it is.

Thanks John,
    Larry


-- 
Larry Williamson               Focus Automation Systems Inc.
watmath!focsys!larry                Waterloo, Ontario
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