Date: Sat, 25 Oct 2003 12:46:10 -0700 From: David Schultz <das@FreeBSD.ORG> To: Sean Hamilton <sh@bel.bc.ca> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Passthrough block device Message-ID: <20031025194610.GB18230@VARK.homeunix.com> In-Reply-To: <005b01c398ed$87070080$0300000a@antalus> References: <005b01c398ed$87070080$0300000a@antalus>
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On Wed, Oct 22, 2003, Sean Hamilton wrote: > Does FreeBSD support a device that will allow for the passing of all reads > and writes on it to a userland application? I wish to handle swapping > myself, preferably without any kernel hacking. > > What would happen if the kernel decided to swap out such a process? As far as I know, the only way to do that in FreeBSD is to implement a userland NFS server (e.g. amd(8)) on the local machine, have the kernel connect to localhost, and have your applications mmap() storage from that volume. (You probably won't be able to swap to the local NFS server without deadlocking.) People have implemented better solutions than that with some degree of OS support, however. Take a look at Mach's external pagers [1] and LRVM[2]. [1] http://citeseer.nj.nec.com/rashid87machineindependent.html [2] http://citeseer.nj.nec.com/satyanarayanan94lightweight.html
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