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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT 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 5CCA4C43441 for ; Thu, 29 Nov 2018 14:44:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2635F213A2 for ; Thu, 29 Nov 2018 14:44:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Ejnt8E0w" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2635F213A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387959AbeK3BuP (ORCPT ); Thu, 29 Nov 2018 20:50:15 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:36586 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732558AbeK3BuO (ORCPT ); Thu, 29 Nov 2018 20:50:14 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id wATEhxOC050421; Thu, 29 Nov 2018 14:44:06 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=pQRTRhE4leFWVUUi359adxmWDFpZDGGOx4uesRG53YM=; b=Ejnt8E0wNqtXpVFlL+rpAU3sjXT+/sy1IIgAqF4HT4uy9XcWc5EG7Js93v7So+/FqBka Npk6sGNJvmRpTeE5uvJpxl16MtyfJ3Rlg0O3j2Fz3Pvt6qHBEDwroE8xyFC4SorGnTym jWMgNGiCRT8QmjNzBQFIrvv3V0P3XoDp1/GeyBNEd/NdWS2v3Hp931hpDvZVxCTE7O9R 9W9c1Oj+6Aqht4IObumHG0/P030GZR8NR5c5wrNltQv35AuCTSZOw7MS5tEj3B0gMjG1 50UwA7u2HSa04wVaoZYAu2c4bc0rg//LlHzOGqwD8mM0r+b0d+LAZVzh0MA6sRfTG//7 kg== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by aserp2120.oracle.com with ESMTP id 2nxxkqrhva-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 29 Nov 2018 14:44:06 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id wATEi5pX012169 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 29 Nov 2018 14:44:05 GMT Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id wATEi4bB032629; Thu, 29 Nov 2018 14:44:04 GMT Received: from char.us.oracle.com (/10.152.32.25) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 29 Nov 2018 06:44:04 -0800 Received: by char.us.oracle.com (Postfix, from userid 1000) id 715FE6A00FB; Thu, 29 Nov 2018 09:44:00 -0500 (EST) Date: Thu, 29 Nov 2018 09:44:00 -0500 From: Konrad Rzeszutek Wilk To: Thomas Gleixner Cc: LKML , x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Jiri Kosina , Tom Lendacky , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Tim Chen , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Greg KH , Dave Stewart , Kees Cook Subject: Re: [patch V2 09/28] x86/Kconfig: Select SCHED_SMT if SMP enabled Message-ID: <20181129144400.GJ32259@char.us.oracle.com> References: <20181125183328.318175777@linutronix.de> <20181125185004.337452245@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181125185004.337452245@linutronix.de> User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9091 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811290124 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 25, 2018 at 07:33:37PM +0100, Thomas Gleixner wrote: > CONFIG_SCHED_SMT is enabled by all distros, so there is not a real point to > have it configurable. The runtime overhead in the core scheduler code is > minimal because the actual SMT scheduling parts are conditional on a static > key. > > This allows to expose the scheduler's SMT state static key to the > speculation control code. Alternatively the scheduler's static key could be > made always available when CONFIG_SMP is enabled, but that's just adding an > unused static key to every other architecture for nothing. > > Signed-off-by: Thomas Gleixner Reviewed-by: Konrad Rzeszutek Wilk > > --- > arch/x86/Kconfig | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1001,13 +1001,7 @@ config NR_CPUS > to the kernel image. > > config SCHED_SMT > - bool "SMT (Hyperthreading) scheduler support" > - depends on SMP > - ---help--- > - SMT scheduler support improves the CPU scheduler's decision making > - when dealing with Intel Pentium 4 chips with HyperThreading at a > - cost of slightly increased overhead in some places. If unsure say > - N here. > + def_bool y if SMP > > config SCHED_MC > def_bool y > >