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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 904CDC2B9F8 for ; Tue, 25 May 2021 17:24:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F19B61378 for ; Tue, 25 May 2021 17:24:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233839AbhEYR0C (ORCPT ); Tue, 25 May 2021 13:26:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229926AbhEYRZy (ORCPT ); Tue, 25 May 2021 13:25:54 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2EF2C061574 for ; Tue, 25 May 2021 10:24:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description; bh=o5bFZZx4+5hZCEtN64VRrO77CmVLQFfTKZ1IOxkh7y4=; b=EQu9zvAjEeMWS3RIcy4/8iIvIc rM3SCfgb5Cboq+HFpszga4LKRa3UNIRGi27YMHHvxFJeomRiT2HPi+WEr9NILr4j/FFGY5Z6a33iU tZ5apUog7W+F+OzOcSl9hDVz4KUvrJwKOwD/EnCYBSS9ssCJ2+FihV3B5aRI6/u8oHX4Y9Z6W49V4 wAlGc3LOOce9N0EVwSKzk3RuZnNOZ5FhEgYErurzUssV+xFOlJbH0TIK3CPYvDC6GGRk6ChBVaUMP /Ft07qk+DhIvRfJP3xiK0abmxuGEvqjZVhjkIgfkyfJK6IW0rlR+KLf4gCEjFQ2wPjuOJWWjsHl72 w5zdfJ3g==; Received: from [2601:1c0:6280:3f0::7376] by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1llamt-006q9u-3w; Tue, 25 May 2021 17:24:15 +0000 Subject: Re: [PATCH] sched: Add CONFIG_SCHED_CORE help text To: Peter Zijlstra , Hugh Dickins Cc: linux-kernel@vger.kernel.org, joel@joelfernandes.org, Ingo Molnar , juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, Valentin Schneider References: From: Randy Dunlap Message-ID: Date: Tue, 25 May 2021 10:24:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/25/21 12:05 AM, Peter Zijlstra wrote: > Subject: sched: Add CONFIG_SCHED_CORE help text > From: Peter Zijlstra > Date: Tue May 25 08:53:28 CEST 2021 > > Hugh noted that the SCHED_CORE Kconfig option could do with a help > text. > > Requested-by: Hugh Dickins > Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Randy Dunlap Thanks. > --- > kernel/Kconfig.preempt | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > --- a/kernel/Kconfig.preempt > +++ b/kernel/Kconfig.preempt > @@ -104,4 +104,18 @@ config SCHED_CORE > bool "Core Scheduling for SMT" > default y > depends on SCHED_SMT > + help > + This option permits Core Scheduling, a means of coordinated task > + selection across SMT siblings. When enabled -- see > + prctl(PR_SCHED_CORE) -- task selection ensures that all SMT siblings > + will execute a task from the same 'core group', forcing idle when no > + matching task is found. > + > + Use of this feature includes: > + - mitigation of some (not all) SMT side channels; > + - limiting SMT interference to improve determinism and/or performance. > + > + SCHED_CORE is default enabled when SCHED_SMT is enabled -- when > + unused there should be no impact on performance. > + > > -- ~Randy