From owner-freebsd-hackers Wed Jul 14 12:29:49 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from herring.nlsystems.com (nlsys.demon.co.uk [158.152.125.33]) by hub.freebsd.org (Postfix) with ESMTP id 6055C14D13 for ; Wed, 14 Jul 1999 12:29:31 -0700 (PDT) (envelope-from dfr@nlsystems.com) Received: from salmon.nlsystems.com (salmon.nlsystems.com [10.0.0.3]) by herring.nlsystems.com (8.9.3/8.8.8) with ESMTP id UAA45182; Wed, 14 Jul 1999 20:29:44 +0100 (BST) (envelope-from dfr@nlsystems.com) Date: Wed, 14 Jul 1999 20:29:44 +0100 (BST) From: Doug Rabson To: "Chris G. Demetriou" Cc: Jon Ribbens , Alfred Perlstein , "Daniel C. Sobral" , freebsd-hackers@freebsd.org, tech-userlevel@netbsd.org, tech@openbsd.org Subject: Re: Replacement for grep(1) (part 2) In-Reply-To: <87oghfz278.fsf@redmail.redback.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 14 Jul 1999, Chris G. Demetriou wrote: > Doug Rabson writes: > > Overcommit can be used for many reasons. I use it to reserve a large > > linear address space to mmap alpha i/o spaces [...] > > Overcommit can be used for many reasons, but unless you've > misdescribed what you're doing, _that's not one of them_. > > The mapped I/O pages need no backing store to be allocated for them by > the VM system. They're backed by hardware. > > And if you have 'placeholder' pages (I note that you didn't say you > mmap all of alpha i/o space, just reserve a large linear address space > in which to mmap it), then it should be possible to map them in such a > way (e.g. read-only ZFOD) in which they wouldn't count against backing > store requirements, either. I certainly don't need or want backing store for these pages. The original reserved region is never touched without first mapping device pages onto it. -- Doug Rabson Mail: dfr@nlsystems.com Nonlinear Systems Ltd. Phone: +44 181 442 9037 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message