On Sat, Dec 13, 2008 at 11:40:11AM -0600, Eric Sandeen wrote:

Martin Steigerwald wrote:

quoted

At the moment it appears to me that disabling write cache may often give 
more performance than using barriers. And this doesn't match my 
expectation of write barriers as a feature that enhances performance. 

Why do you have that expectation?  I've never seen barriers advertised
as enhancing performance.  :)

I do wonder why barriers on, write cache off is so slow; I'd have
thought the barriers were a no-op.  Maybe I'm missing something.

Barriers still enforce ordering in this case, so it affects the
elevator algorithm....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com