From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756923AbdKOIRK (ORCPT ); Wed, 15 Nov 2017 03:17:10 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:36873 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751230AbdKOIRA (ORCPT ); Wed, 15 Nov 2017 03:17:00 -0500 X-Google-Smtp-Source: AGs4zMYq7I7VqThh9gvZjiz3aqOYr8wBG7ZlNmEHxgtfmllvoZvxQahT4MyxPocfB2qDRNoxlqCvAA== Date: Wed, 15 Nov 2017 09:16:56 +0100 From: Ingo Molnar To: "quan.xu04@gmail.com" Cc: "linux-kernel@vger.kernel.org" , kvm , Quan Xu , Peter Zijlstra Subject: Re: [PATCH RFC v3 4/6] Documentation: Add three sysctls for smart idle poll Message-ID: <20171115081656.at4cllb53pprfbtz@gmail.com> References: <1510570064-6178-1-git-send-email-quan.xu0@gmail.com> <20171113150842.epdffyxhlu5nq37u@gmail.com> <35da8c93-95fb-8bf0-8538-4e1ef5f126f4@gmail.com> <20171114074410.c5h5zg43xtcmelez@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * quan.xu04@gmail.com wrote: > > > could I only leave paravirt_poll_threshold_ns parameter (the maximum poll time), > > > which is as similar as "adaptive halt-polling" Wanpeng mentioned.. then user can > > > turn it off, or find an appropriate threshold for some odd scenario.. > > That way lies utter madness. Maybe add it as a debugfs knob, but exposing it to > > userspace: NAK. > > > .. so, I will make these 3 parameters by default in next v4. >      paravirt_poll_threshold_ns = 200000 >      paravirt_poll_shrink = 2 >      paravirt_poll_grow = 2 > > neither touch the syscal ABI nor expose it to userspace again. Note that you can still expose it to developers via debugfs knobs. I.e. same development and testing flexibility, but no ABI promise and an implicit expectation for this mechanism to be self-tuning. Thanks, Ingo