Re: Striping CLOG and Subtrans

On Sat, 2005-12-03 at 11:49 -0500, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > These changes have almost no negative impact on run time performance and
> > can be implemented with minimum change. We can discuss whether the false
> > sharing phenomena actually occurs, but the bottom line ISTM is that if
> > we can avoid it ever occurring, for almost free, then why not? 
> 
> No, you've put the burden of proof in the wrong place.  You are
> proposing a significant logical complication in the code for a
> completely hypothetical improvement --- there is *no* evidence on
> the table that cache contention within clog pages is even measurable.
> Show us some experimental numbers first.

In a way, I agree with you on the burden of proof. 

Code wise: I'm not sure this represents a significant logical
complication. There would be no more code than there is now, changes
would be isolated to about 3 places in two files.

There is no evidence either way, is all I would add. But we do have
strong indications that it is likely. It's gonna be hard to come up with
a smoking gun. We'll have to rethink our performance testing regime to
include some larger scale testing with instrumentation.

Shelved until measurements indicate requirement.

Best Regards, Simon Riggs