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=-15.8 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,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 3EE84C2B9F8 for ; Tue, 25 May 2021 07:07:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1DB0B6138C for ; Tue, 25 May 2021 07:07:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231470AbhEYHI0 (ORCPT ); Tue, 25 May 2021 03:08:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230366AbhEYHIW (ORCPT ); Tue, 25 May 2021 03:08:22 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD9C2C061574 for ; Tue, 25 May 2021 00:06:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=94rRe8DncEJ8thzWN8Ue22a749mm1JoE2gXK/Suv76I=; b=LXm8J+MJAO2E9OxBokUduDn+o9 eaN62R+9BYqrcFHGciKpn4s5Ur83WArkjKGmlt0q/nPRanDYYecA4I3xH88lavr7h4cfWAvcE6rpR T4mCUkv1M9w7nNZJQ2X30gj0txVOlUbZh4GQzO4wyHhHtswRIKaau58Mg5TrEnamm8MICEBRjs+Vm fmQYicstPYK8BCCUFp78HQuAVP26iVD23UJbUmiwUuMTpM84aSAM5+aJ6Fz1+FG0B2X8s1dD5AqG9 qIbA8+qMdbpRTLfm2NkfQKeBrT/1jJ9YvYi/4TwZ1WAI3xetdmxjWaerxcE/AGHipMWK6IJeVZ4e5 eVjgwI+Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1llR89-003DLT-DO; Tue, 25 May 2021 07:05:38 +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) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 13055300258; Tue, 25 May 2021 09:05:27 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id CC55030E92289; Tue, 25 May 2021 09:05:27 +0200 (CEST) Date: Tue, 25 May 2021 09:05:27 +0200 From: Peter Zijlstra To: Hugh Dickins Cc: linux-kernel@vger.kernel.org, rdunlap@infradead.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 Subject: [PATCH] sched: Add CONFIG_SCHED_CORE help text 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 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) --- 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. +