From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A39DC4363D for ; Wed, 7 Oct 2020 12:29:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08742206D9 for ; Wed, 7 Oct 2020 12:29:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="eY65VnS9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728181AbgJGM30 (ORCPT ); Wed, 7 Oct 2020 08:29:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:49192 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727253AbgJGM3Z (ORCPT ); Wed, 7 Oct 2020 08:29:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1602073764; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=V5IGfljwHBccTu4EnUAuGHAEO7WK+XuDIhx9cYCdy2Q=; b=eY65VnS9rBQbaDJPW7r95aCTaRmGsQzEJKdrVNI3mA8t2dTGk7SKze/lsyN8dISFDP8oYm rCaZLEdP9Tb/pOhsyHxKKikCjlZRtD4QupiJpHcH2Zs26zSX6OP9WUUY+BxFJ+2MgDg8NN t2Dzv+bbjjunlPYfMuFhG2h7UlXzR7E= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9FAE9ADEC; Wed, 7 Oct 2020 12:29:24 +0000 (UTC) Date: Wed, 7 Oct 2020 14:29:23 +0200 From: Michal Hocko To: Peter Zijlstra Cc: Thomas Gleixner , Frederic Weisbecker , LKML , Mel Gorman , Ingo Molnar Subject: Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE, PREEMPT_VOLUNTARY on kernel command line Message-ID: <20201007122923.GJ29020@dhcp22.suse.cz> References: <20201007120401.11200-1-mhocko@kernel.org> <20201007121939.GE2628@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201007121939.GE2628@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 07-10-20 14:19:39, Peter Zijlstra wrote: > On Wed, Oct 07, 2020 at 02:04:01PM +0200, Michal Hocko wrote: > > From: Michal Hocko > > > > Many people are still relying on pre built distribution kernels and so > > distributions have to provide mutliple kernel flavors to offer different > > preemption models. Most of them are providing PREEMPT_NONE for typical > > server deployments and PREEMPT_VOLUNTARY for desktop users. > > Is there actually a benefit to NONE? We were recently talking about > removing it. I believe Mel can provide much better insight. We have been historically using PREEMPT_NONE for our enterprise customers mostly for nice throughput numbers. Many users are really targeting throughput much more than latencies. My understanding is that even though VOLUNTARY preemption model doesn't add too many preemption points on top of NONE it is still something that is observable (IIRC 2-3% on hackbench). > The much more interesting (runtime) switch (IMO) would be between > VOLUNTARY and PREEMPT. Absolutely and as said we are looking into that. This is meant to be a first baby step in that direction. Still very useful in our current situation when we want to provide both NONE and VOLUNTARY. -- Michal Hocko SUSE Labs