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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3211E92720 for ; Thu, 5 Oct 2023 17:16:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231469AbjJERQL (ORCPT ); Thu, 5 Oct 2023 13:16:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231599AbjJERPH (ORCPT ); Thu, 5 Oct 2023 13:15:07 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 475FA3AB4 for ; Thu, 5 Oct 2023 10:07:24 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BEEFBC15; Thu, 5 Oct 2023 10:08:02 -0700 (PDT) Received: from [10.1.197.60] (eglon.cambridge.arm.com [10.1.197.60]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 01E193F5A1; Thu, 5 Oct 2023 10:07:20 -0700 (PDT) Message-ID: <331b165a-f650-37fd-7990-2704c668f6f2@arm.com> Date: Thu, 5 Oct 2023 18:07:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v6 12/24] x86/resctrl: Add cpumask_any_housekeeping() for limbo/overflow Content-Language: en-GB To: Reinette Chatre , x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com References: <20230914172138.11977-1-james.morse@arm.com> <20230914172138.11977-13-james.morse@arm.com> From: James Morse In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Reinette, On 03/10/2023 22:15, Reinette Chatre wrote: > On 9/14/2023 10:21 AM, James Morse wrote: >> The limbo and overflow code picks a CPU to use from the domain's list >> of online CPUs. Work is then scheduled on these CPUs to maintain >> the limbo list and any counters that may overflow. >> >> cpumask_any() may pick a CPU that is marked nohz_full, which will >> either penalise the work that CPU was dedicated to, or delay the >> processing of limbo list or counters that may overflow. Perhaps >> indefinitely. Delaying the overflow handling will skew the bandwidth >> values calculated by mba_sc, which expects to be called once a second. >> >> Add cpumask_any_housekeeping() as a replacement for cpumask_any() >> that prefers housekeeping CPUs. This helper will still return >> a nohz_full CPU if that is the only option. The CPU to use is >> re-evaluated each time the limbo/overflow work runs. This ensures >> the work will move off a nohz_full CPU once a housekeeping CPU is >> available. >> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c >> index 0bbed8c62d42..993837e46db1 100644 >> --- a/arch/x86/kernel/cpu/resctrl/monitor.c >> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c >> @@ -793,8 +793,10 @@ void cqm_handle_limbo(struct work_struct *work) >> >> __check_limbo(d, false); >> >> - if (has_busy_rmid(d)) >> + if (has_busy_rmid(d)) { >> + cpu = cpumask_any_housekeeping(&d->cpu_mask); >> schedule_delayed_work_on(cpu, &d->cqm_limbo, delay); >> + } >> > > ok - but if you do change the CPU the worker is running on then > I also expect d->cqm_work_cpu to be updated. Otherwise the offline > code will not be able to determine if the worker needs to move. Good point - I missed this. Thanks, James