From owner-freebsd-hackers Wed Feb 10 17:19:42 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id RAA24093 for freebsd-hackers-outgoing; Wed, 10 Feb 1999 17:19:42 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id RAA24088 for ; Wed, 10 Feb 1999 17:19:41 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.2/8.9.1) id RAA87393; Wed, 10 Feb 1999 17:19:34 -0800 (PST) (envelope-from dillon) Date: Wed, 10 Feb 1999 17:19:34 -0800 (PST) From: Matthew Dillon Message-Id: <199902110119.RAA87393@apollo.backplane.com> To: Terry Lambert Cc: dyson@iquest.net, tlambert@primenet.com, dg@root.com, kuku@gilberto.physik.RWTH-Aachen.DE, hackers@FreeBSD.ORG Subject: Re: portability of shm, mmap, pipes and socket IPC References: <199902110059.RAA26636@usr08.primenet.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> > backing object. :> :> The condition for paging out pages to SysV SHM are very similar to anonymous :> MMAPed regions. There is no effective difference. If you use file backed :> MMAPed regions, there are some time consuming sync operations though. : :The difference is that anonymous MMAPed regions can only be mapped :into multiple processes via forke based inheritance. : :This makes them useless for sotheming that, for example, attaches to :a shared context segment shared by several processes acting as :work-to-do engines, so as to be able to examine and manipulate the :shared idea of the current context contents. : :This limitation is the specific reason that NetWare for UNIX uses shared :memory segments instead of mmap'ed regions for client context records. : : : Terry Lambert : terry@lambert.org ... and has absolutely nothing to do with the question that John was replying to, which was related to the fault overhead/expense of using mmap() verses a SYS-V shared memory segment. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message