Re: [patch] sched: minimalist select_idle_sibling() bouncing cowsyndrome fix

[Ingo Molnar]

* Mike Galbraith <bitbucket@xxxxxxxxx> wrote:

> On Mon, 2013-01-28 at 11:53 +0100, Ingo Molnar wrote: 
> > * Mike Galbraith <bitbucket@xxxxxxxxx> wrote:
> > 
> > > If the previous CPU is cache affine and idle, select it.
> > 
> > No objections in principle - but would be nice to have a 
> > changelog with numbers, % of improvement included and so?
> 
> Well, that like was my changelog, guess it needs improvement.
> 
> Take 2.
> 
> sched: minimalist select_idle_sibling() bouncing cow syndrome fix
> 
> If the previous CPU is cache affine and idle, select it.
> 
> The current implementation simply traverses the sd_llc domain,
> taking the first idle CPU encountered, which walks buddy pairs
> hand in hand over the package, inflicting excruciating pain.
> 
> 1 tbench pair (worst case) in a 10 core + SMT package:
> 
> pre   15.22 MB/sec 1 procs
> post 252.01 MB/sec 1 procs

Drool ... :-)

What would be a 'contrarian' test - i.e. a test where this could 
hurt most?

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/