Re: [PATCH 3/4] XFS: Return case-insensitive match for dentry cache

["Barry Naujok" <bnaujok@xxxxxxx>]

On Thu, 15 May 2008 14:57:00 +1000, Christoph Hellwig <hch@xxxxxxxxxxxxx>  
wrote:
> On Wed, May 14, 2008 at 05:55:45PM +1000, Barry Naujok wrote:
> > Not quite sure if this is the right test, but I did 1000 creates on
> > a brand new filesystem with and without ci on my SATA drive, both
> > sustained almost 600 creates per second.
> >
> > I believe creates would be the worst case scenario for not adding
> > negative dentries?
> No, negative dentries shouldn't have any effect on that.  negative
> entries help to optimize away lookups.  E.g. thing of the PATH variable
> and say your shell is not in the first directory listed there.  Having
> a negative dentry for it means that you don't have to do a lookup in
> the first directories everytime someone wants to use the shell.
Ah, that makes more sense. I did a test of a million lookups to a
non-existant file in a short-form directory (dual 1.6G opteron):

CI = 4.6s
non-CI = 3.7s

And a directory with 10000 files:

CI = 10.3s
non-CI = 3.9s

Barry.