Messages in this thread | | | Date | Sat, 08 Dec 2001 03:15:50 +0300 | From | Hans Reiser <> | Subject | Re: [reiserfs-dev] Re: Ext2 directory index: ALS paper and benchmarks |
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Ragnar Kjørstad wrote:
>On Sat, Dec 08, 2001 at 12:01:20AM +0300, Hans Reiser wrote: > >>>In the cases I've studied more closely (e.g. maildir cases) the problem >>>with reiserfs and e.g. the tea hash is that there is no common ordering >>>between directory entries, stat-data and file-data. >>> >>>When new files are created in a directory, the file-data tend to be >>>allocated somewhere after the last allocated file in the directory. The >>>ordering of the directory-entry and the stat-data (hmm, both?) are >>> >>no, actually this is a problem for v3. stat data are time of creation >>ordered (very roughly speaking) >>and directory entries are hash ordered, meaning that ls -l suffers a >>major performance penalty. >> > >Yes, just remember that file-body ordering also has the same problem. >(ref the "find . -type f | xargs cat > /dev/null" test wich I think >represent maildir performance pretty closely) > > > So is this a deeply inherent drawback of offering readdir name orders that differ hugely from time of creation order?
The advantages of sorting for non-linear search time are obvious.....
I suppose we could use objectids based on the hash of the first assigned filename plus a 60 bit global to the FS counter....
but it is too many bits I think. I think that using substantially less than the full hash of the name that is used for directory entry keys doesn't work.... Comments welcome.
Hans
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