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

Borislav Petkov
2012-09-24T19:22:24Z

On Mon, Sep 24, 2012 at 12:12:18PM -0700, Linus Torvalds wrote:
> On Mon, Sep 24, 2012 at 11:26 AM, Mike Galbraith <efault@gmx.de> wrote:
> >
> > 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.
>
> Oh, I agree with trying to avoid HT threads, the resource contention
> easily gets too bad.
>
> It's more a question of "if we have real cores with separate L1's but
> shared L2's, go with those first, before we start distributing it out
> to separate L2's".

Yes, this is exactly what I meant before. We basically want to avoid
unnecessary, high-volume probe traffic over the L3 or memory controller,
if possible.

So, trying harder to select an L2 sibling would be more beneficial,
IMHO, instead of scanning the whole node.

--
Regards/Gruss,
Boris.