Re: [patch 2/2] MM: allow per-cpu vmstat_threshold and vmstat_worker configuration

[Marcelo Tosatti <mtosatti@redhat.com>]

On Fri, May 12, 2017 at 11:07:48AM -0500, Christoph Lameter wrote:
> On Fri, 12 May 2017, Marcelo Tosatti wrote:
> 
> > In our case, vmstat updates are very rare (CPU is dominated by DPDK).
> 
> What is the OS doing on the cores that DPDK runs on? I mean we here can
> clean a processor of all activities and are able to run for a long time
> without any interruptions.
> 
> Why would you still let the OS do things on that processor? If activities
> by the OS are required then the existing NOHZ setup already minimizes
> latency to a short burst (and Chris Metcalf's work improves on that).
> 
> 
> What exactly is the issue you are seeing and want to address? I think we
> have similar aims and as far as I know the current situation is already
> good enough for what you may need. You may just not be aware of how to
> configure this.

I want to disable vmstat worker thread completly from an isolated CPU.
Because it adds overhead to a latency target, target which 
the lower the better.

> I doubt that doing inline updates will do much good compared to what we
> already have and what the dataplan mode can do.

Can the dataplan mode disable vmstat worker thread completly on a given
CPU?