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=-5.8 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 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 8396FC48BE5 for ; Wed, 16 Jun 2021 11:39:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 553D261246 for ; Wed, 16 Jun 2021 11:39:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232432AbhFPLlS (ORCPT ); Wed, 16 Jun 2021 07:41:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230330AbhFPLlS (ORCPT ); Wed, 16 Jun 2021 07:41:18 -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 27AB2C061574 for ; Wed, 16 Jun 2021 04:39:12 -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=XtPVmlK1jzNcS6yikiAXkTW3U1VbjKSd7AQa7GX2l+U=; b=VSgy1b2rGNHUdtv6AvJhe9MoyG AKi+vmOnYWJUTGcxuTNWvLMC/rl9iF+YsUXJB6LsdJGQFYcyXqKPzo0ixn/biXUm5JPQ8eiNTkU/u VkRxuKu/wMdsQX1ad6X6M+HbVsASs4PnR3ys8uHVBHqKQk0fNeQZBfjTkYmm1KVj6BHA4TO0PFMOG y/5qnEADPOzXpig5vmQ9nyQnCu+5m/HMeThvECxCyB/fFEcuDN9QuurX0uFm/snGH9GE0An9sykDG zNv4o6LY7CKZYhMJ3anW6uuda+E8tCL5RMZb9ZKwUyAcKoH6ru7ouJPPuMan8e4VUsSW+4H33r9dF /XbblJAQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1ltTsp-008JFs-Uw; Wed, 16 Jun 2021 11:39:06 +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 (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 30571300204; Wed, 16 Jun 2021 13:39:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0079520C169EA; Wed, 16 Jun 2021 13:39:05 +0200 (CEST) Date: Wed, 16 Jun 2021 13:39:05 +0200 From: Peter Zijlstra To: Ley Foon Tan Cc: Vincent Guittot , Ingo Molnar , Quentin Perret , Greg KH , Dietmar Eggemann , linux-kernel@vger.kernel.org Subject: Re: sched: Question about big and little cores system with SMP and EAS Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 16, 2021 at 07:29:26PM +0800, Ley Foon Tan wrote: > Hi all > > Would like to ask the experts here regarding the Symmetric > Multi-Processing mode (SMP) with Energy aware scheduler (EAS) support > on the big + little cores system. And the you ask a question unrelated to either Symmetric MP or EAS :-) > Hardware system: > Big and little cores have almost the same ISA, but the big core has > some extension instructions that little core doesn't have. That problem is unrelated to big.Little / EAS, also by definition that is not SMP seeing how the 'S' is a blatant lie. The simplest solution is to simply disallow usage of the extended ISA and force mandate the common subset. The complicated answer is something along the lines of: https://lkml.kernel.org/r/20210608180313.11502-1-will@kernel.org