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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 74792C433E1 for ; Fri, 14 Aug 2020 05:18:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B27720771 for ; Fri, 14 Aug 2020 05:18:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726247AbgHNFSK (ORCPT ); Fri, 14 Aug 2020 01:18:10 -0400 Received: from mga04.intel.com ([192.55.52.120]:65440 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbgHNFSK (ORCPT ); Fri, 14 Aug 2020 01:18:10 -0400 IronPort-SDR: 9WPhhedK0i03mCWO2yt/54idOG65O+ScOAXe4X/nJbjYgsB05plAYH9aFGu2yHK+UMxTrvZYty uDTIvNd8Ds3A== X-IronPort-AV: E=McAfee;i="6000,8403,9712"; a="151773961" X-IronPort-AV: E=Sophos;i="5.76,311,1592895600"; d="scan'208";a="151773961" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2020 22:18:09 -0700 IronPort-SDR: AtRzbQvay8Kd0BLezy/923tIK69BjTo82BJho3OinqGvljQ+y5zpDVbUpD4M6czzA5PN4/0SbK Wc9Mp99OAl/w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,311,1592895600"; d="scan'208";a="318773271" Received: from cli6-desk1.ccr.corp.intel.com (HELO [10.239.161.135]) ([10.239.161.135]) by fmsmga004.fm.intel.com with ESMTP; 13 Aug 2020 22:18:02 -0700 Subject: Re: [RFC PATCH 00/16] Core scheduling v6(Internet mail) To: =?UTF-8?B?YmVuYmppYW5nKOiSi+W9qik=?= Cc: Joel Fernandes , "viremana@linux.microsoft.com" , Nishanth Aravamudan , Julien Desfossez , Peter Zijlstra , Tim Chen , Ingo Molnar , Thomas Glexiner , Paul Turner , Linus Torvalds , LKML , Subhra Mazumdar , Frederic Weisbecker , Kees Cook , Greg Kerr , Phil Auld , Aaron Lu , Aubrey Li , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , Vineeth Pillai , Chen Yu , Christian Brauner , "Ning, Hongyu" References: <6d0f9fc0-2e34-f559-29bc-4143e6d3f751@linux.intel.com> <20200809164408.GA342447@google.com> <162a03cc-66c3-1999-83a2-deaad5aa04c8@linux.intel.com> <20200812230850.GA3511387@google.com> <5a39735d-dfd8-bdec-f068-81895799640e@linux.intel.com> <89d973d1-1302-17a6-c647-ea7c538c2747@linux.intel.com> <18263ED7-88B3-4DED-9714-55D9D2EB69D9@tencent.com> From: "Li, Aubrey" Message-ID: <97a82444-77ab-dbd2-f765-0d818f94ca0b@linux.intel.com> Date: Fri, 14 Aug 2020 13:18:02 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <18263ED7-88B3-4DED-9714-55D9D2EB69D9@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/8/14 12:04, benbjiang(蒋彪) wrote: > > >> On Aug 14, 2020, at 9:36 AM, Li, Aubrey wrote: >> >> On 2020/8/14 8:26, benbjiang(蒋彪) wrote: >>> >>> >>>> On Aug 13, 2020, at 12:28 PM, Li, Aubrey wrote: >>>> >>>> On 2020/8/13 7:08, Joel Fernandes wrote: >>>>> On Wed, Aug 12, 2020 at 10:01:24AM +0800, Li, Aubrey wrote: >>>>>> Hi Joel, >>>>>> >>>>>> On 2020/8/10 0:44, Joel Fernandes wrote: >>>>>>> Hi Aubrey, >>>>>>> >>>>>>> Apologies for replying late as I was still looking into the details. >>>>>>> >>>>>>> On Wed, Aug 05, 2020 at 11:57:20AM +0800, Li, Aubrey wrote: >>>>>>> [...] >>>>>>>> +/* >>>>>>>> + * Core scheduling policy: >>>>>>>> + * - CORE_SCHED_DISABLED: core scheduling is disabled. >>>>>>>> + * - CORE_COOKIE_MATCH: tasks with same cookie can run >>>>>>>> + * on the same core concurrently. >>>>>>>> + * - CORE_COOKIE_TRUST: trusted task can run with kernel >>>>>>>> thread on the same core concurrently. >>>>>>>> + * - CORE_COOKIE_LONELY: tasks with cookie can run only >>>>>>>> + * with idle thread on the same core. >>>>>>>> + */ >>>>>>>> +enum coresched_policy { >>>>>>>> + CORE_SCHED_DISABLED, >>>>>>>> + CORE_SCHED_COOKIE_MATCH, >>>>>>>> + CORE_SCHED_COOKIE_TRUST, >>>>>>>> + CORE_SCHED_COOKIE_LONELY, >>>>>>>> +}; >>>>>>>> >>>>>>>> We can set policy to CORE_COOKIE_TRUST of uperf cgroup and fix this kind >>>>>>>> of performance regression. Not sure if this sounds attractive? >>>>>>> >>>>>>> Instead of this, I think it can be something simpler IMHO: >>>>>>> >>>>>>> 1. Consider all cookie-0 task as trusted. (Even right now, if you apply the >>>>>>> core-scheduling patchset, such tasks will share a core and sniff on each >>>>>>> other. So let us not pretend that such tasks are not trusted). >>>>>>> >>>>>>> 2. All kernel threads and idle task would have a cookie 0 (so that will cover >>>>>>> ksoftirqd reported in your original issue). >>>>>>> >>>>>>> 3. Add a config option (CONFIG_SCHED_CORE_DEFAULT_TASKS_UNTRUSTED). Default >>>>>>> enable it. Setting this option would tag all tasks that are forked from a >>>>>>> cookie-0 task with their own cookie. Later on, such tasks can be added to >>>>>>> a group. This cover's PeterZ's ask about having 'default untrusted'). >>>>>>> (Users like ChromeOS that don't want to userspace system processes to be >>>>>>> tagged can disable this option so such tasks will be cookie-0). >>>>>>> >>>>>>> 4. Allow prctl/cgroup interfaces to create groups of tasks and override the >>>>>>> above behaviors. >>>>>> >>>>>> How does uperf in a cgroup work with ksoftirqd? Are you suggesting I set uperf's >>>>>> cookie to be cookie-0 via prctl? >>>>> >>>>> Yes, but let me try to understand better. There are 2 problems here I think: >>>>> >>>>> 1. ksoftirqd getting idled when HT is turned on, because uperf is sharing a >>>>> core with it: This should not be any worse than SMT OFF, because even SMT OFF >>>>> would also reduce ksoftirqd's CPU time just core sched is doing. Sure >>>>> core-scheduling adds some overhead with IPIs but such a huge drop of perf is >>>>> strange. Peter any thoughts on that? >>>>> >>>>> 2. Interface: To solve the performance problem, you are saying you want uperf >>>>> to share a core with ksoftirqd so that it is not forced into idle. Why not >>>>> just keep uperf out of the cgroup? >>>> >>>> I guess this is unacceptable for who runs their apps in container and vm. >>> IMHO, just as Joel proposed, >>> 1. Consider all cookie-0 task as trusted. >>> 2. All kernel threads and idle task would have a cookie 0 >>> In that way, all tasks with cookies(including uperf in a cgroup) could run >>> concurrently with kernel threads. >>> That could be a good solution for the issue. :) >> >> From uperf point of review, it can trust cookie-0(I assume we still need >> some modifications to change cookie-match to cookie-compatible to allow >> ZERO and NONZERO run together). >> >> But from kernel thread point of review, it can NOT trust uperf, unless >> we set uperf's cookie to 0. > That’s right. :) > Could we set the cookie of cgroup where uperf lies to 0? > IMHO the disadvantage is that if there are two or more cgroups set cookie-0, then the user applications in these cgroups could run concurrently on a core, though all of them are set as trusted, we made a hole of user->user isolation. Thanks, -Aubrey