[Ocfs2-devel] Ocfs2 performance bugs of doom

[Mark Fasheh]

On Tue, Mar 07, 2006 at 04:34:12AM +0100, Andi Kleen wrote:
> Did you actually do some statistics how long the hash chains are? 
> Just increasing hash tables blindly has other bad side effects, like
> increasing cache misses.
Yep, the gory details are at:

http://oss.oracle.com/~mfasheh/lock_distribution.csv

This measure was taken about 18,000 locks into a kernel untar. The only
change was that I switched things to only hash the last 18 characters of
lock resource names.

In short things aren't so bad that a larger hash table wouldn't help. We've
definitely got some peaks however. Our in-house laboratory of mathematicians
(read: Bill Irwin) is checking out methods by which we can smooth things out
a bit more :)
	--Mark

--
Mark Fasheh
Senior Software Developer, Oracle
mark.fasheh at oracle.com