From owner-freebsd-hackers Mon Jun 28 1:42:27 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (Postfix) with ESMTP id D233A14CC0 for ; Mon, 28 Jun 1999 01:42:24 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id BAA18494; Mon, 28 Jun 1999 01:41:58 -0700 (PDT) (envelope-from dillon) Date: Mon, 28 Jun 1999 01:41:58 -0700 (PDT) From: Matthew Dillon Message-Id: <199906280841.BAA18494@apollo.backplane.com> To: "Daniel J. O'Connor" Cc: Ladavac Marino , freebsd-hackers@FreeBSD.ORG, Zhihui Zhang Subject: Re: RE: Implementation of mmap() in FreeBSD References: Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> [ML] It is possible to handle these cases in VM code, by :> trapping on any access to the partial page, and allowing only those :> accesses which are withing the originally requested range. Performance :> would suck without end, though. : :Well it would only suck for access to that page right, which wouldn't be too :bad unless the program in question thrashes out the partial pages. : :--- :Daniel O'Connor software and network engineer I don't think this would be workable. It would fail utterly on small files -- every single access would be trapped. The system must be reasonably deterministic. Programmers have a reasonable expectation that accesses to mmap'd areas are, for in-core pages, instantanious. Otherwise they wouldn't bother to use mmap and instead would use read() and write() :-) -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message