On Thu, 15 May 2008 14:57:00 +1000, Christoph Hellwig <hch@infradead.org>  
wrote:

quoted text
> 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.
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