From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752794AbbBJHvQ (ORCPT ); Tue, 10 Feb 2015 02:51:16 -0500 Received: from mail-wi0-f174.google.com ([209.85.212.174]:62150 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752642AbbBJHux (ORCPT ); Tue, 10 Feb 2015 02:50:53 -0500 Message-ID: <54D9B857.7080500@redhat.com> Date: Tue, 10 Feb 2015 08:50:47 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Christian Borntraeger , linux-kernel@vger.kernel.org, kvm@vger.kernel.org CC: riel@redhat.com, mtosatti@redhat.com, rkrcmar@redhat.com, jan.kiszka@siemens.com, dmatlack@google.com Subject: Re: [PATCH] kvm: add halt_poll_ns module parameter References: <1423226937-11169-1-git-send-email-pbonzini@redhat.com> <54D92005.2060308@de.ibm.com> In-Reply-To: <54D92005.2060308@de.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/02/2015 22:00, Christian Borntraeger wrote: > I can confirm that this also helps uperf with a 1/1 byte round trip work load > between guests on s390. And I can confirm the higher CPU load. This is normally > a no-go for the typical s390 users, which utilize their systems as much as > possible. Your check for single_task_running could actually solve that > problem because on overcommitment this will never switch to polling if the > runqueues get full. > Since this is also runtime configurable and defaults to 0 it should be pretty > painless. > > The only question is: is there a sane way of doing autotuning? The answer is: we'll see. :) I have some ideas, I have to run them through the necessary experiments. Paolo