From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Metcalf Subject: Re: [PATCH] nohz: prevent tilegx network driver interrupts Date: Mon, 20 Jul 2015 18:15:44 -0400 Message-ID: <55AD7310.40000@ezchip.com> References: <1436549624-16104-1-git-send-email-cmetcalf@ezchip.com> <20150710182406.GC26428@lerouge> <55A0175E.2010200@ezchip.com> <20150711143033.GE10257@lerouge> <55AD6684.3080607@ezchip.com> <20150720214943.GC13032@lerouge> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Cc: , To: Frederic Weisbecker Return-path: In-Reply-To: <20150720214943.GC13032@lerouge> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 07/20/2015 05:49 PM, Frederic Weisbecker wrote: > On Mon, Jul 20, 2015 at 05:22:12PM -0400, Chris Metcalf wrote: >> On 07/11/2015 10:30 AM, Frederic Weisbecker wrote: >>> On Fri, Jul 10, 2015 at 03:05:02PM -0400, Chris Metcalf wrote: >>>> The tilegx chips typically don't do cpu offlining anyway, since >>>> we've never really found a usecase, so whatever you boot with >>>> you always have available. We do have support for a bare-metal >>>> mode which you can run on some of the cores, so you may start >>>> with fewer than cpu_possible actually running, but it will always >>>> be that same set of cores. >>> And that bare metal mode runs out of Linux? >> The bare metal environment runs on cpus that have been marked >> as unavailable to Linux, so Linux just sees them as permanently >> offlined. There is a BME driver (which we haven't upstreamed, >> since the BME isn't upstreamed either) that arranges to share >> memory between the BME and Linux. >> >> I don't think that many customers are using the BME in any >> case. We push all of them towards using our dataplane mode >> instead, since it almost always works just as well from a >> performance perspective, and is easier to develop code for. > So bare metal mode is different than dataplane mode, right? > Where bare metal mode offlines the CPU and IIUC dataplane mode > instead uses CPUs that are available to Linux, just isolated > with nohz and various affinity stuff, right? Yes, exactly. Cores running the bare metal environment are NOT running Linux at all, just talking directly to the Tilera hypervisor. -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com