Re: Linux: more cores = less concurrency.

--- On Mon, 11/4/11, Scott Marlowe <scott.marlowe@gmail.com> wrote:

> Just FYI, in synthetic pgbench type benchmarks, a 48 core
> AMD Magny
> Cours with LSI HW RAID and 34 15k6 Hard drives scales
> almost linearly
> up to 48 or so threads, getting into the 7000+ tps
> range.  With SW
> RAID it gets into the 5500 tps range.
>

I'll have to try with the synthetic benchmarks next then, but somethings definately going off here.  I'm seeing no disk
activityat all as they're selects and all pages are in ram. 

I was wondering if anyone had any deeper knowledge of any kernel tunables, or anything else for that matter.

A wild guess is something like multiple cores contending for cpu cache, cpu affinity, or some kind of contention in the
kernel,alas a little out of my depth. 

It's pretty sickening to think I can't get anything else out of more than 8 cores.