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

Linus Torvalds
2012-09-25T03:33:07Z

On Mon, Sep 24, 2012 at 8:20 PM, Mike Galbraith <efault@gmx.de> wrote:
>
> Yes. Cross wiring traverse _start_ points should eliminate (well, damp)
> bounce as well without killing the 1:N latency/preempt benefits of large
> L3 packages.

Yes, a "test buddy first, then check the other cores in the package"
hybrid approach might be reasonable.

Of course, that's effectively what the whole "prev_cpu" thing is kind
of supposed to also do, isn't it? Because it's even lovelier if you
can avoid bouncing around by trying to hit a previous CPU that might
just have some of the old data in the caches still.

Linus