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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DBBC5EB64D7 for ; Fri, 16 Jun 2023 12:48:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345328AbjFPMs1 (ORCPT ); Fri, 16 Jun 2023 08:48:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344254AbjFPMs0 (ORCPT ); Fri, 16 Jun 2023 08:48:26 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0370297F for ; Fri, 16 Jun 2023 05:48:24 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0D1696115E for ; Fri, 16 Jun 2023 12:48:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B895C433C8; Fri, 16 Jun 2023 12:48:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686919703; bh=T9+U4Djd/HXnHrFKYN+j+1Mj6rD45TKf1gAvy2c4JqQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Qp7kzElcTUC7RODPj8v+KsFrkrI0ocR1kNf0mXz5KsMRdPLDiM16VIRFlqDWap/dR YyucVfYtlB91MoBVR9ytYWB4izH6dzxCVJQqCWy5OxDfQwn3MOFARty580tdHat0mN 0qga+HbFczmQKBSRzyy+QlEWlDXcHSjbY7mzAaLbfa2dgqiD+7Dbf8jOGWMj7cdqms pXx+X3MVr9xKxZhXVomyVP5eN/rMWEmdRaQm2K3xmjQ8nkkhVyunwVinYxjX0gzYEB 1e8GNa6vxhepaSwWNB+MPJ3o0FGwgguXclve6vnxy3AFlzHXcztpiHB6kp3l3XOjnb MOIKBtuy/jukw== Message-ID: Date: Fri, 16 Jun 2023 14:48:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [RFC PATCH V3 6/6] sched/fair: Implement starvation monitor To: Peter Zijlstra Cc: Joel Fernandes , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org, Luca Abeni , Tommaso Cucinotta , Thomas Gleixner , Vineeth Pillai , Shuah Khan References: <841849b5-1f9c-4f0e-2de8-1da278256888@kernel.org> <20230616120507.GM83892@hirez.programming.kicks-ass.net> Content-Language: en-US From: Daniel Bristot de Oliveira In-Reply-To: <20230616120507.GM83892@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/16/23 14:05, Peter Zijlstra wrote: > On Tue, Jun 13, 2023 at 03:41:30PM +0200, Daniel Bristot de Oliveira wrote: > >> In an 0-laxity scheduler, the server would run at 0-laxity, jumping in >> front of DL tasks... that would break EDF. It would be mixing two >> schedulers in one. It is not required and likely not a good idea either. > > I did consider a hybrid 0-laxity and EDF scheduler for mixed > criticality, as have others like Ted Baker IIRC. IIRC it can be done > using an augmented tree, but none of that solves the problems 0-laxity > has (like over preemption and the general problem of playing chicken by > doing things at the *VERY* last possible moment). There are papers here or there about it, but it is far from being the most explored way to do mixed criticality because of these side effects. It is more common to have virtual deadlines for high and low criticalities, while using EDF. Having EDF and being working conserving makes our life easier for other points we are way behind, i.e., deadline inheritance. > I think I did a talk at OSPERT on this at some point many years ago. > Luckily some bright fellow had this semi-partitioned stuff that would > make live much simpler :-) It will, we can have two partitions, one for high and one for low. The general case in the low power CPU, and if it does not make to finish on it, it continues in the high power one. Still, always using EDF. Having virtual deadline is part of semi-part. Anyways, EDF schedules more, and it is simpler... it is hard to beat. This patch set is a warm up for that... -- Daniel