Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken

On 1/10/2012 6:41 AM, Peter Zijlstra wrote:

On Tue, 2012-01-10 at 06:32 -0800, Arjan van de Ven wrote:

quoted

a very good default would be to keep all tasks on one package until half
the cores in the package are busy, and then start spreading out. 

Does that still make sense when there's strong NUMA preference? By
forcing stuff on a single package you increase the number of remote
memory fetches (which generally generate more stalls), also the memory
controllers need to stay awake anyway.

the memory controllers need to stake regardless of what you do;
it's more a memory bandwidth kind of thing.

if you have an enormous numa factor (>= 10 or so), then you really need
a completely different policy I suspect.
Thankfully those are rare.