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 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 0036EC388F9 for ; Fri, 23 Oct 2020 07:45:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 657F42177B for ; Fri, 23 Oct 2020 07:45:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="VrC8dvAl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S374624AbgJWHpt (ORCPT ); Fri, 23 Oct 2020 03:45:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S374437AbgJWHps (ORCPT ); Fri, 23 Oct 2020 03:45:48 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A13FCC0613CE; Fri, 23 Oct 2020 00:45:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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=C8iPz4vR/r/Z7txUMN6zv8MlJSlNHAYC9PuCCf3WrRc=; b=VrC8dvAl/nH2owuVmhXvcwABwo lys5ud6TqV2KhOz+wIgITmag1I/hBL7cTPZmVjcnbdIYzfRmMKHtrKsyZzTfxehMo/aHDDuxQTg7K 3WtU17vINDxt+K4y4pjdOXAnYrqt+z9osguYycfcaTy6WgYtXLfTHOGe/hCWG982LWN7XbZ8hDdGc 6caMD8ui+guG7N9HBp/dFWACDEKIDMBAOl0+QiydHFpidY+/T1JUHcVCrlfqoX0uCe18bH68+Uhol 9TPNJQTsF1SeFyozEbRkTj8CY/KveJ30THdMFs3XyLgGNoMN+Ud7E8YZFd4oPGhOLa36SsLnvGsYp mTma2OcQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVrlg-0004Y1-2n; Fri, 23 Oct 2020 07:45:44 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 901C5300B22; Fri, 23 Oct 2020 09:45:42 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 590CC203D09CB; Fri, 23 Oct 2020 09:45:42 +0200 (CEST) Date: Fri, 23 Oct 2020 09:45:42 +0200 From: Peter Zijlstra To: Elliot Berman Cc: Thomas Gleixner , "Paul E. McKenney" , Jonathan Corbet , Trilok Soni , Prasad Sodagudi , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH] smp: Add bootcpus parameter to boot subset of CPUs Message-ID: <20201023074542.GN2611@hirez.programming.kicks-ass.net> References: <1603404243-5536-1-git-send-email-eberman@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1603404243-5536-1-git-send-email-eberman@codeaurora.org> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, Oct 22, 2020 at 03:04:03PM -0700, Elliot Berman wrote: > In a heterogeneous multiprocessor system, specifying the 'maxcpus' > parameter on kernel command line does not provide sufficient control > over which CPUs are brought online at kernel boot time, since CPUs may > have nonuniform performance characteristics. Thus, add bootcpus kernel > parameter to control which CPUs should be brought online during kernel > boot. When both maxcpus and bootcpus is set, the more restrictive of the > two are booted. Why would one wish to do so? Having the ability for abilities sake is no good.