Re: [PATCH] dentry and inode cache hash algorithm performance changes.

[Dave Hansen <haveblue@us.ibm.com>]

On Fri, 2004-05-07 at 06:04, Jose R. Santos wrote:
> On 05/04/04 13:55:10, Andrew Morton wrote:
> > > Andrew - Is there any workload you want me to run to show that this hash
> > > function is going to be equal or better that the one already provided
> > > in Linux?
> > 
> > Not really - it sounds like you've covered it pretty well.  Did you try SDET?
> > 
> > It could be that reducing the hash table size will turn pretty much any
> > workload into a test of the hash quality.
> 
> Sorry for the late reply...
> 
> Steve Pratt seem to have a SDET setup already and he did me the favor of 
> running SDET with a reduce dentry entry hash table size.  I belive that
> his table suggest that less than 3% change is acceptable variability, but
> overall he got a 5% better number using the new hash algorith.

It's usually best to keep increasing the number of SDET iterations that
you average against, at least until the averages start to become a bit
less bouncy.  Also, mounting ramfs on /tmp can _really_ help lower its
variability, probably because of gcc.  

You might be lucky enough to get some consistently good numbers that
way.

-- Dave