From owner-freebsd-hackers Fri Feb 19 15:25:10 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from smtp02.primenet.com (smtp02.primenet.com [206.165.6.132]) by hub.freebsd.org (Postfix) with ESMTP id 0B1BC11566 for ; Fri, 19 Feb 1999 15:22:39 -0800 (PST) (envelope-from tlambert@usr02.primenet.com) Received: (from daemon@localhost) by smtp02.primenet.com (8.8.8/8.8.8) id QAA08795; Fri, 19 Feb 1999 16:22:29 -0700 (MST) Received: from usr02.primenet.com(206.165.6.202) via SMTP by smtp02.primenet.com, id smtpd008729; Fri Feb 19 16:22:28 1999 Received: (from tlambert@localhost) by usr02.primenet.com (8.8.5/8.8.5) id QAA10132; Fri, 19 Feb 1999 16:20:47 -0700 (MST) From: Terry Lambert Message-Id: <199902192320.QAA10132@usr02.primenet.com> Subject: Re: vm_page_zero_fill To: dillon@apollo.backplane.com (Matthew Dillon) Date: Fri, 19 Feb 1999 23:20:36 +0000 (GMT) Cc: toasty@home.dragondata.com, dyson@iquest.net, tlambert@primenet.com, mike@smith.net.au, hackers@FreeBSD.ORG In-Reply-To: <199902172020.MAA10702@apollo.backplane.com> from "Matthew Dillon" at Feb 17, 99 12:20:50 pm X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > :What if I'm doing a partial read? Is a partial read even possible if I'm > :using the mmap method? > > The filesystem always does a full read even if you only do a partial > read. This is true whether you use read() or access a page w/ mmap(), > but it is doubly true with mmap(). The only exception is the perhaps-not-page-aligned last blocks in the file. In this case, it zero fills the page before the read, in case of subsequent file extension. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message