Messages in this thread |  | | Date | Sat, 08 Dec 2001 00:12:23 +0300 | From | Hans Reiser <> | Subject | Re: [reiserfs-dev] Re: Ext2 directory index: ALS paper and benchmarks |
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Daniel Phillips wrote:
>On December 7, 2001 07:03 pm, Ragnar Kjørstad wrote: > >>>With ReiserFS we see slowdown due to random access even with small >>>directories. I don't think this is a cache effect. >>> >>I can't see why the benefit from read-ahead on the file-data should be >>affected by the directory-size? >> >>I forgot to mention another important effect of hash-ordering: >>If you mostly add new files to the directory it is far less work if you >>almost always can add the new entry at the end rather than insert it in >>the middle. Well, it depends on your implementation of course, but this >>effect is quite noticable on reiserfs. When untaring a big directory of >>maildir the performance difference between the tea hash and a special >>maildir hash was approxemately 20%. The choice of hash should not affect >>the performance on writing the data itself, so it has to be related to >>the cost of the insert operation. >> > >Yes, I think you're on the right track. HTree on the other hand is optimized >for inserting in arbitrary places, it takes no advantage at all of sequential >insertion. (And doesn't suffer from this, because it all happens in cache >anyway - a million-file indexed directory is around 30 meg.) > >-- >Daniel > > someday reiserfs might benefit from inserting more airholes into directories so that insertion is more efficient.
This may be a significant advantage of Htree.
Yet another feature needed.....:-/
Hans
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