Newsgroups: comp.os.minix
Path: utzoo!utgpu!watserv1!hbetel
From: hbetel@watserv1.waterloo.edu (Heather Betel)
Subject: Re: Shared libraries with minix
Message-ID: <1991Jun1.043438.17038@watserv1.waterloo.edu>
Organization: University of Waterloo
References: <3186@krafla.rhi.hi.is> <1991May28.035703.9271@watserv1.waterloo.edu> <3216@krafla.rhi.hi.is>
Date: Sat, 1 Jun 1991 04:34:38 GMT
Lines: 36

In article <3216@krafla.rhi.hi.is> adamd@rhi.hi.is (Adam David) writes:
>hbetel@watserv1.waterloo.edu (Heather [actually Richard] Betel) writes:
>
>The library server has temporary access to the dataspace of the client
>which initiated the library call, because the library routine is executed
>with the user and group ID of the client. The client process has temporary
>access to the library codespace in order to access the library routine.
>
	My point is that this must happen even on MMU systems. On the
8086, your model is fairly simple, but under, say, an 040, the library
server is a different process, with a completely different memory
space. Mapping in the client's space, doing the work, then mapping it
out, for every call is expensive.

>
>I am talking about fundamental operations, and not calling conventions.
>The language-dependent part is in the language-specific library and the
>part which can be shared between languages is in the general (utility)
>library.
>
	Then what is the difference between the library functions and
system calls? You are just putting in another level of indirection!

>>	Like a trap is any better. Instead of trapping, then copying
>>data, you just trap, then copy data! No matter how you cut it, there
>>will be a form of message passing with minix. Check out how a serial
>>interrupt is handled. This won't be faster.
>
>Maybe I misunderstood. I was under the impression that the trap handler
>was guaranteed maximum priority which would be higher than normal IPC
>messages.
	The harddrive controller uses IPC. Are you going to give the
library server higher priority than the harddrive?

Richard (Not Heather) Betel
I am not just a Sibling! I am a free man!