Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!think!snorkelwacker!bloom-beacon!CAEN.ENGIN.UMICH.EDU!billkatt
From: billkatt@CAEN.ENGIN.UMICH.EDU (Steve Bollinger)
Newsgroups: comp.windows.x
Subject: Re: Shared Memory Connection
Message-ID: <4a284a2c2.001011c@caen.engin.umich.edu>
Date: 2 May 90 20:34:23 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 30

>From: rws@expo.lcs.mit.edu (Bob Scheifler)
	
>    Our Stardent GS 1000 (Stellar GS 1000) uses shared memory and we have a 
>    flipbook image which uses GetImage and PutImage to flip over 200 half
>    megabyte images per second.  Try that with sockets.
	
>This example is not to the main point.  In R4 we have an experimental
>extension which uses shared memory for GetImage and PutImage; it doesn't
>require a full shared-memory transport to deal with these requests, and
>in fact it is more appropriate to special-case these requests.  In a
>normal transport, even when it's shared-memory, the PutImage request
>still has to copy from the "source" into the shared-memory transport
>buffer, which is an expensive operation.  Better to just put the image
>itself in shared memory, and send a pointer to it, which is what our
>extension does.
	
Ahh..  Yes, the Stellar uses a setup with just a shared memory connection,
with copying and such instead of sockets, not like your experimental extension.

I would say that images are going to be a bigger and bigger percentage of
the data used in X, with the visualization explosion.  It would be a good
idea to get a jump on anything which does speed them up.

Heck, I think the most significant addition to X in the near future will be
when bitmaps are compressed and expanded using that new standard (20 & 40 : 1)
before being sent over the network.  This won't speed up local stuff, but a
lot of what people do with X lately is across networks from fast machine to
slow ones.

-Steve Bollinger