On Wed, Mar 20, 2013 at 06:49:49PM -0700, Daniel Phillips wrote: > On Tue, Mar 19, 2013 at 11:54 PM, Rob Landley <rob@xxxxxxxxxxx> wrote: > > I'm confused, http://tux3.org/ lists a bunch of dates from 5 years ago, then > > nothing. Is this project dead or not? > > Not. We haven't done much about updating tux3.org lately, however you > will find plenty of activity here: > > https://github.com/OGAWAHirofumi/tux3/tree/master/user > > You will also find fairly comprehensive updates on where we are and > where this is going, here: > > http://phunq.net/pipermail/tux3/ > > At the moment we're being pretty quiet because of being in the middle > of developing the next-gen directory index. Not such a small task, as > you might imagine. Hi Daniel, The "next-gen directory index" comment made me curious. I wanted to know if there's anything I could learn from what you are doing and whether anything of your new algorithms could be applied to, say, the XFS directory structure to improve it. I went looking for design docs and found this: http://phunq.net/pipermail/tux3/2013-January/001938.html In a word: Disappointment. Compared to the XFS directory structure, the most striking architectural similarity that I see is this: "the file bteee[sic] effectively is a second directory index that imposes a stable ordering on directory blocks". That was the key architectural innovation in the XFS directory structure that allowed it to provide the correct seekdir/telldir/NFS readdir semantics and still scale. i.e. virtually mapped directory entries. I explained this layout recently here: http://marc.info/?l=linux-ext4&m=136081996316453&w=2 http://marc.info/?l=linux-ext4&m=136082221117399&w=2 http://marc.info/?l=linux-ext4&m=136089526928538&w=2 We could swap the relevant portions of your PHTree design doc with my comments (and vice versa) and both sets of references would still make perfect sense. :P Further, the PHTree description of tag based freespace tracking is rather close to how XFS uses tags to track free space regions, including the fact that XFS can be lazy at updating global free space indexes. The global freespace tree indexing is slightly different to the XFS method - it's closer to the original V1 dir code in XFS (that didn't scale at all well) than the current code. However, that's really a fine detail compared to all the major structural and algorithmic similarities. Hence it appears to me that at a fundamental level PHTree is just a re-implementation of the XFS directory architecture. It's definitely a *major* step forward from HTree, but it can hardly be considered revolutionary or "next-gen". It's not even state of the art. Hence: disappointment. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
