Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected

Mike Galbraith
2012-09-24T18:26:42Z

On Mon, 2012-09-24 at 18:54 +0200, Peter Zijlstra wrote:
> On Mon, 2012-09-24 at 09:30 -0700, Linus Torvalds wrote:

> > Also, do we really want to spread things out that aggressively?
> > How/why do we know that we don't want to share L2 caches, for example?
> > It sounds like a bad idea from a power standpoint, and possibly
> > performance too.
>
> IIRC this current stuff is the result of Mike and Suresh running a few
> benchmarks.. Mike, Suresh, either one of you remember this? Otherwise
> I'll have to go trawl the archives.

Aside from the cache pollution I recall having been mentioned, on my
E5620, cross core is a tbench win over affine, cross thread is not.

-Mike