Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!dawn.crd.ge.COM!stpeters
From: stpeters@dawn.crd.ge.COM (Dick St.Peters)
Newsgroups: comp.windows.x
Subject: Re: Memory for Pixmaps - DEC Pmax Xcfb2 server.
Message-ID: <8910311809.AA19789@dawn.crd.Ge.Com>
Date: 31 Oct 89 18:09:39 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 18

> At MIT we've hacked together a server extension to support shared-memory
> pixmaps (data shared between client and server), which results in a PutImage
> having approximately the same performance as a CopyArea.  It doesn't work
> across a network, of course, but it's basically about as fast as you can go.

Under SunOS 4.0, processes on different machines can share (virtual)
memory, by mmap()'ing the same file (NFS-mounted on at least one of
the machines).  This doesn't get rid of the network bottleneck, of
course, but the kernel's paging mechanism is likely to outperform
explicit program IO.  There are all sorts of questions about
synchronization and how well coherence is maintained among two
physical memories and the file, etc., that I do not have answers to.
I've only seen this done once; it may not be practical.  However, it
certainly is interesting.

--
Dick St.Peters, GE Corporate R&D, Schenectady, NY
stpeters@dawn.crd.ge.com	uunet!dawn.crd.ge.com!stpeters