From owner-freebsd-hackers Mon Nov 12 15:21:35 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from pintail.mail.pas.earthlink.net (pintail.mail.pas.earthlink.net [207.217.120.122]) by hub.freebsd.org (Postfix) with ESMTP id 77F8337B419 for ; Mon, 12 Nov 2001 15:21:30 -0800 (PST) Received: from dialup-209.245.136.188.dial1.sanjose1.level3.net ([209.245.136.188] helo=mindspring.com) by pintail.mail.pas.earthlink.net with esmtp (Exim 3.33 #1) id 163QOM-0006kG-00; Mon, 12 Nov 2001 15:21:26 -0800 Message-ID: <3BF059A7.12FA60F3@mindspring.com> Date: Mon, 12 Nov 2001 15:22:15 -0800 From: Terry Lambert Reply-To: tlambert2@mindspring.com X-Mailer: Mozilla 4.7 [en]C-CCK-MCD {Sony} (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Matthew Dillon Cc: Jason Mawdsley , freebsd-hackers@FreeBSD.ORG Subject: Re: mmap/madvise References: <200111081947.fA8JlAe03457@web.cs.ndsu.nodak.edu> <02ae01c16891$4c1f4970$2a64a8c0@macadamian.com> <3BEB0A57.3C510C49@mindspring.com> <019401c16959$4e64a8b0$2a64a8c0@macadamian.com> <200111121036.fACAaiv75199@apollo.backplane.com> <3BF05303.FEC66C7A@mindspring.com> <200111122302.fACN2C306926@apollo.backplane.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Matthew Dillon wrote: He was writing a virtual memory manger of his own that resembled the Windows version of one he wrote, in order to port software to UNIX (most likely Linux and not FreeBSD, if you were to look at the web site for his company). > Simply using a pre-written file does not really guarentee > anything... after all, you can run out of space on the > filesystem as easily as you can run out of VM, and if you > store other things, like configuration data, in the same > filesystem, you are just as vulnerable to bad programming > in the event of a write() filesystem-full failure as you > are vulnerable to overcomitting the VM system to the point > where it starts killing processes. If you precommit the disk space, then it is impossible for you to run out later. The answer to the "if you store other things" arguement is "precommit *all* contendable resources". I think he wants to avoid failure testing out the ying-yang in his fast path, which is a reasonable thing to want. I know you like overcommit, and trusting the system to do the right thing, but this is not FreeBSD specific code he is writing here, so bending his code around the FreeBSD implementation would be bad. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message