Date: Wed, 14 Jul 1999 20:29:44 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: "Chris G. Demetriou" <cgd@netbsd.org> Cc: Jon Ribbens <jon@oaktree.co.uk>, Alfred Perlstein <bright@rush.net>, "Daniel C. Sobral" <dcs@newsguy.com>, freebsd-hackers@freebsd.org, tech-userlevel@netbsd.org, tech@openbsd.org Subject: Re: Replacement for grep(1) (part 2) Message-ID: <Pine.BSF.4.10.9907142028470.58023-100000@salmon.nlsystems.com> In-Reply-To: <87oghfz278.fsf@redmail.redback.com>
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On 14 Jul 1999, Chris G. Demetriou wrote: > Doug Rabson <dfr@nlsystems.com> 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
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