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=-8.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7F512C4338F for ; Wed, 28 Jul 2021 17:04:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51F9360FED for ; Wed, 28 Jul 2021 17:04:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230286AbhG1REC (ORCPT ); Wed, 28 Jul 2021 13:04:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21332 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229515AbhG1RD7 (ORCPT ); Wed, 28 Jul 2021 13:03:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1627491837; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=DsHibXntA5nrdCKJ3pn/OIwa0FmfD/AJLSfptD0KLdY=; b=h0uMlroN1SESeuWMbfAdRynyaKGaovE8S4Wr1qqh1H6qyPxaDAEF8bvF3zKnxUW87zisD+ AQSASAlL9Fj5QEc4Hc3gOxsH0mP4sDOCnHck7TSvhwoIRbYh0S+wNMhUGq0vse3u4LOs3t 6J3r3YkqSYm+GUaVkLiFrtBVuqRSNRc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-559-w4UBFodnMoa8M9yeBZxIqQ-1; Wed, 28 Jul 2021 13:03:56 -0400 X-MC-Unique: w4UBFodnMoa8M9yeBZxIqQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1B4FF1026201; Wed, 28 Jul 2021 17:03:55 +0000 (UTC) Received: from fuller.cnet (ovpn-112-3.gru2.redhat.com [10.97.112.3]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3895310016F7; Wed, 28 Jul 2021 17:03:48 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 83F644172EDB; Wed, 28 Jul 2021 13:21:21 -0300 (-03) Date: Wed, 28 Jul 2021 13:21:21 -0300 From: Marcelo Tosatti To: Nitesh Lal Cc: Nicolas Saenz Julienne , Frederic Weisbecker , linux-kernel@vger.kernel.org, Christoph Lameter , Juri Lelli , Peter Zijlstra , Alex Belits , Peter Xu , Thomas Gleixner Subject: Re: [patch 1/4] add basic task isolation prctl interface Message-ID: <20210728162121.GB24635@fuller.cnet> References: <7b2d6bf91d30c007e19a7d2cbddcb2460e72d163.camel@redhat.com> <20210727110050.GA502360@fuller.cnet> <20210727130930.GB283787@lothringen> <20210727145209.GA518735@fuller.cnet> <20210727234539.GH283787@lothringen> <20210728093707.GA3242@fuller.cnet> <20210728131610.GA11900@fuller.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 28, 2021 at 11:00:01AM -0400, Nitesh Lal wrote: > > > A latency sensitive > > > application might be OK with the former but not with the latter. > > > > Two alternatives: > > > > 1) The pattern above, where particular subsystems that might interrupt > > the kernel are enabled automatically if the kernel supports it. > > > > Pros: > > Applications which implement this only need to be changed once, > > and can benefit from new kernel features. > > > > Applications can disable particular features if they turn > > out to be problematic. > > > > Cons: > > New features might break applications. > > > > 2) Force applications to enable each new feature individually. > > > > Pros: Won't cause regressions, kernel behaviour is explicitly > > controlled by userspace. > > > > Cons: Apps won't benefit from new features automatically. > > > > --- > > > > It seems to me 1) is preferred. Can also add a sysfs control to > > have a "default_isolation_feature" flag, which can be changed > > by a sysadmin in case a new feature is undesired. > > > > Thoughts? > > > > > The first option may work specifically with the sysfs interface that you > mentioned, however, IMHO (2) is safer than regressing the workloads. Also, > if the previously implemented controls are good enough for the workload > then there should not be a need to enable the new ones. OK, can set default_isolation_feature as 0 then, which admin can configure to a non-default value. This would enable the new features only if the admin enables them. Thanks.