From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linda Knippers Subject: Re: [RFC] new free space caching stuff Date: Tue, 26 May 2009 12:12:21 -0400 Message-ID: <4A1C14E5.2050601@hp.com> References: <20090521184351.GC11101@dhcp231-156.rdu.redhat.com> <20090522141133.GA8762@think> Reply-To: linda.knippers@hp.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: Chris Mason , Josef Bacik , linux-btrfs@vger.kernel.org Return-path: In-Reply-To: <20090522141133.GA8762@think> List-ID: Chris Mason wrote: > On Thu, May 21, 2009 at 02:43:52PM -0400, Josef Bacik wrote: >> Hello, >> >> Okay I'm looking at redoing all of this stuff again, and I'd like to make this >> the last time, so I'm going to outline what we currently have, what the problems >> are with it, and what I want to do. I would appreciate any/all input so I can >> try and get this right the first time. >> > > Josef and I hashed this out someone on IRC. I think the bitmaps alone > aren't going to scale all that well for huge filesystems, so he is > looking into a hybrid bitmap/extent approach based on the size of the > free space. I don't know if this is of any interest but I thought I'd provide a pointer to the AdvFS design spec for space allocation. http://advfs.svn.sourceforge.net/viewvc/advfs/advfs_design_docs_v1/porting_designs/storage_allocation.pdf?revision=1 The Tru64 version of AdvFS used bitmaps but this was changed during the port to HP-UX to use a combination of b-trees. Both the original and new designs are discussed in section 2 of the spec and there's a description of other design options considered but then rejected. The docs in the original tarball I posted were not very user friendly so I checked them into an svc tree to make them a little easier to browse. If it will be useful, I can do the same with the source code. -- ljk > -chris > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html