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 A7E0CC6FA82 for ; Tue, 27 Sep 2022 13:01:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232005AbiI0NBb (ORCPT ); Tue, 27 Sep 2022 09:01:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231588AbiI0NB1 (ORCPT ); Tue, 27 Sep 2022 09:01:27 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 120FAA2209 for ; Tue, 27 Sep 2022 06:01:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JajMUTWFWdf52LEvQ3sdkC4KhamKYR9MOGDGh7+XACA=; b=UBtsrGDqWvvym8LUIXYIIW653+ ia4Y+PnhWnbokr6Rn0/I9FQCCO3A8142BQhLdTYyK96xplEyXFQRfHHQi9q64fg9+uvStOY/oqfo1 P4eNU+/9IuPx4KEoA1PRjnyC0X3rctkoyBy03qhpNENCT8NzEw/7uW6C+zFLdvghOeGtivtjFwlgQ e87NSRAKcz9/9Bhi9+KhFFzdZGotAK1XQxu6RS7zQ6f+mm8zwI09ZW/8aVdJey+ZBqnmb3obCjgWg 6vUYbDVHNY/rS6dZ5bzglqv80ypOHMt38503jiDYjc4DCdhs25/JplTkb8KbptK4NwRZYJg1sG0HO W/wcO+rQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1odACy-00GHzB-C7; Tue, 27 Sep 2022 13:01:08 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E295B3001D6; Tue, 27 Sep 2022 15:01:07 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BFDDD2BDF120B; Tue, 27 Sep 2022 15:01:07 +0200 (CEST) Date: Tue, 27 Sep 2022 15:01:07 +0200 From: Peter Zijlstra To: Ricardo Neri Cc: Juri Lelli , Vincent Guittot , Ricardo Neri , "Ravi V. Shankar" , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Len Brown , Mel Gorman , "Rafael J. Wysocki" , Srinivas Pandruvada , Steven Rostedt , Tim Chen , Valentin Schneider , x86@kernel.org, linux-kernel@vger.kernel.org, "Tim C . Chen" Subject: Re: [RFC PATCH 01/23] sched/task_struct: Introduce classes of tasks Message-ID: References: <20220909231205.14009-1-ricardo.neri-calderon@linux.intel.com> <20220909231205.14009-2-ricardo.neri-calderon@linux.intel.com> <20220916144112.GA29395@ranerica-svr.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220916144112.GA29395@ranerica-svr.sc.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 16, 2022 at 07:41:13AM -0700, Ricardo Neri wrote: > At least on Intel processors, class 0 is a valid class. The scheduler needs to > have a notion of unclassified tasks and decide how to handle them, IMO. > > Intel processors currently support 8-bit, unsigned classes. I doubt other > architectures will ever support more than 256 classes. Short can handle all the > possible classification values and also the unclassified case. > > On the other hand, class 0 could be the default classification unless hardware > classifies differently. 0 would be special and need to be documented clearly. > This would work for Intel processors. You can always do: class = hw_class + 1; that makes 0 'special' and the hardware class can be trivially reconstructed by subtracting 1.