From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 0/8] RFC: vcpu pinning at qemu start Date: Tue, 04 Mar 2008 15:10:06 -0300 Message-ID: <47CD907E.1080607@redhat.com> References: <12046477213193-git-send-email-gcosta@redhat.com> <47CD8A02.50402@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, chrisw@sous-sol.org, avi@qumranet.com To: Anthony Liguori Return-path: In-Reply-To: <47CD8A02.50402@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Anthony Liguori wrote: > Glauber Costa wrote: >> Hi guys, >> >> Here's a first series of patch aiming at vcpu pinning support in qemu. >> Ideally, as vcpu as just normal threads, the usual userspace tools can >> be used >> to set cpu affinities mask. >> >> However, It makes it very difficult to _start_ a vm with vcpus pinned, >> since >> we don't know the thread ids from qemu in advance, nor do we know when >> are the >> vcpus created. >> >> The patches introduce a -cpu-map option, that, if specified, starts >> the virtual cpus >> with the specified affinities. >> >> Comments? Welcome. Random rants? Not welcome, but... how can I stop >> you? So go ahead! >> >> > > So why exactly is this useful? I have a hard time constructing a > reasonable use-case in my mind for something like this. My main interest is in management tools being able to specify pinning set ups at VM creation time. As I said, it can be done through tools like taskset, but then you'd have to know: * when are the threads created * which thread ids corresponds to each cpu And of course, for an amount of time, the threads will be running in a "wrong" cpu, which may affect workloads running there. (which is a case cpu pinning usually tries to address) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/