From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [patch 2/2] MM: allow per-cpu vmstat_threshold and vmstat_worker configuration Date: Fri, 12 May 2017 13:19:16 -0300 Message-ID: <20170512161915.GA4185@amt.cnet> References: <20170425135717.375295031@redhat.com> <20170425135846.203663532@redhat.com> <20170502102836.4a4d34ba@redhat.com> <20170502165159.GA5457@amt.cnet> <20170502131527.7532fc2e@redhat.com> <20170512122704.GA30528@amt.cnet> <20170512154026.GA3556@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Rik van Riel , Linux RT Users , cmetcalf@mellanox.com To: Christoph Lameter Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org 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?