Re: Ext2 directory index, updated

[Andreas Dilger]

On Nov 06, 2001  00:13 +0100, Daniel Phillips wrote:
> > > From 2.4.10 on ext2 has an accelerator in 
> > > ext2_find_entry - it caches the last lookup position.  I'm wondering how 
> > > that affects this case.
> > 
> > From the description I read a while ago, I believe it could cause a
> > significant speedup.
> > 
> > I'll have to try that out one of these days.
> 
> I noticed split results with the find_entry accelerator, at least in its 
> current form: faster delete, slower create.

Well, according to reiserfs benchmarks at:
http://namesys.com/benchmarks/mongo/2.4.8_vs_2.4.9_vs_2.4.10_table.txt

the accelerator speeds up stat times (in all cases) by a factor of 3 to 5.
Create times are reduced as well (although not as much).  In fact, it also
shows delete speed as being slower, but that is hard to quantify as the
reiserfs delete spped is slower also.

It actually looks like both ext2 and reiserfs took a hit in the read
department in 2.4.10 as well.  Maybe a bad interaction with the page
cache or something?  It would also be worthwhile to go back to the
addition of directories-in-pagecache as well, because I seem to recall
posting about a hit in read performance at that time as well, and never
really heard anything about it.

The bonnie++ benchmark doesn't show any obvious trends (incomplete tables):
http://namesys.com/benchmarks/bonnie/2.4.8_2.4.9_2.4.10.txt

I'll have to go and update my bonnie benchmarks for newer kernels (last
run when testing indexed directores and dir-in-pagecache at 2.4.5).

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/