Re: Re: [PATCH 1/3]fs/inode: iunique() Optimize Performance

[Matthew Wilcox <matthew@wil.cx>]

On Tue, Dec 01, 2009 at 09:21:32PM +0800, Liuweni wrote:
> Hi Matthew Wilcox:
> 	I got the code note as the following. if there is no performance problem, 
> maybe the code note need update.
> 
> 
> ------
>  *	BUGS:
>  *	With a large number of inodes live on the file system this function
>  *	currently becomes quite slow.
> 

I don't believe that comment is correct.  In any case, your optimisation
wouldn't make a lick of difference to the speed; it's a single comparison
in a loop which also calculates a hash, makes a function call, and walks
the length of a hash chain.

The old adage about debugging code, not comments applies here.  Don't take
somebody else's word for it that there's a performance problem here.
Devise a test to demonstrate the performance problem.  Otherwise, how
will you know if you solved it?

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."