Date: Thu, 24 May 2007 09:57:14 +0000 From: Darren Reed <darrenr@freebsd.org> To: Bruce Evans <brde@optusnet.com.au> Cc: Craig Boston <craig@xfoil.gank.org>, Pawel Jakub Dawidek <pjd@freebsd.org>, freebsd-fs@freebsd.org, freebsd-current@freebsd.org, Kris Kennaway <kris@obsecurity.org>, Vince <jhary@unsane.co.uk> Subject: Re: ZFS committed to the FreeBSD base. Message-ID: <20070524095714.GA52149@hub.freebsd.org> In-Reply-To: <20070523212559.V10628@besplex.bde.org> References: <20070410011125.GB38535@xor.obsecurity.org> <20070410013034.GC8189@nowhere> <20070410014233.GD8189@nowhere> <4651BD6F.5050301@unsane.co.uk> <20070522083112.GA5136@hub.freebsd.org> <4652B15D.5060505@unsane.co.uk> <20070523085532.GA27542@hub.freebsd.org> <20070523093231.GA29797@xor.obsecurity.org> <20070523100631.GA30143@xor.obsecurity.org> <20070523212559.V10628@besplex.bde.org>
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On Wed, May 23, 2007 at 09:45:16PM +1000, Bruce Evans wrote: > On Wed, 23 May 2007, Kris Kennaway wrote: > > >On Wed, May 23, 2007 at 05:32:31AM -0400, Kris Kennaway wrote: > > > >>I would actually be interested to know how Solaris gets away with > >>this. It sounds like there must be less of a distinction between > >>memory allocated to the kernel and to userland, and the ability for > >>memory to flow between these two with some form of backpressure when > >>userland wants memory that is currently gobbled by up solaris ZFS. > >> > >>This kind of system probably makes good sense (although maybe there > >>are trade-offs), but anyway it's not how FreeBSD does it. > > > >After some further thought I guess the difference is just that on a > >64-bit kernel you don't have KVA issues and can indeed map all of > >physical RAM into the kernel for caching. > > This should probably happen for 64-bit kernels in FreeBSD too. FreeBSD > sizes the buffer map part of KVA in the same way on all arches, to squeeze > it into the limited available space on i386's, and has large complexity > and some loss of performance in the buffer cache in order to work with > the limited KVA. (Very old versions had less complexity and a large loss > of performance.) Do we support variable page sizes in the kernel for amd64? Darren
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