From nobody Sun Feb 8 20:33:09 2026 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 34C36C001DF for ; Fri, 28 Jul 2023 16:45:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233947AbjG1Qpx (ORCPT ); Fri, 28 Jul 2023 12:45:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235176AbjG1QpQ (ORCPT ); Fri, 28 Jul 2023 12:45:16 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9108A4EC3 for ; Fri, 28 Jul 2023 09:43:54 -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 C4FD21570; Fri, 28 Jul 2023 09:44:33 -0700 (PDT) Received: from merodach.members.linode.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0A62D3F67D; Fri, 28 Jul 2023 09:43:47 -0700 (PDT) From: James Morse To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , James Morse , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, xingxin.hx@openanolis.org, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com Subject: [PATCH v5 11/24] x86/resctrl: Add cpumask_any_housekeeping() for limbo/overflow Date: Fri, 28 Jul 2023 16:42:41 +0000 Message-Id: <20230728164254.27562-12-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20230728164254.27562-1-james.morse@arm.com> References: <20230728164254.27562-1-james.morse@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: James Morse --- Changes since v3: * typos fixed Changes since v4: * Made temporary variables unsigned --- arch/x86/kernel/cpu/resctrl/internal.h | 23 +++++++++++++++++++++++ arch/x86/kernel/cpu/resctrl/monitor.c | 17 ++++++++++++----- 2 files changed, 35 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/r= esctrl/internal.h index 7c2a1c235480..a32d307292a1 100644 --- a/arch/x86/kernel/cpu/resctrl/internal.h +++ b/arch/x86/kernel/cpu/resctrl/internal.h @@ -7,6 +7,7 @@ #include #include #include +#include #include =20 #define L3_QOS_CDP_ENABLE 0x01ULL @@ -55,6 +56,28 @@ /* Max event bits supported */ #define MAX_EVT_CONFIG_BITS GENMASK(6, 0) =20 +/** + * cpumask_any_housekeeping() - Choose any CPU in @mask, preferring those = that + * aren't marked nohz_full + * @mask: The mask to pick a CPU from. + * + * Returns a CPU in @mask. If there are housekeeping CPUs that don't use + * nohz_full, these are preferred. + */ +static inline unsigned int cpumask_any_housekeeping(const struct cpumask *= mask) +{ + unsigned int cpu, hk_cpu; + + cpu =3D cpumask_any(mask); + if (tick_nohz_full_cpu(cpu)) { + hk_cpu =3D cpumask_nth_andnot(0, mask, tick_nohz_full_mask); + if (hk_cpu < nr_cpu_ids) + cpu =3D hk_cpu; + } + + return cpu; +} + struct rdt_fs_context { struct kernfs_fs_context kfc; bool enable_cdpl2; diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/re= sctrl/monitor.c index c268aa5925c7..f0670795b446 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -767,9 +767,9 @@ static void mbm_update(struct rdt_resource *r, struct r= dt_domain *d, void cqm_handle_limbo(struct work_struct *work) { unsigned long delay =3D msecs_to_jiffies(CQM_LIMBOCHECK_INTERVAL); - int cpu =3D smp_processor_id(); struct rdt_resource *r; struct rdt_domain *d; + int cpu; =20 mutex_lock(&rdtgroup_mutex); =20 @@ -778,8 +778,10 @@ void cqm_handle_limbo(struct work_struct *work) =20 __check_limbo(d, false); =20 - if (has_busy_rmid(d)) + if (has_busy_rmid(d)) { + cpu =3D cpumask_any_housekeeping(&d->cpu_mask); schedule_delayed_work_on(cpu, &d->cqm_limbo, delay); + } =20 mutex_unlock(&rdtgroup_mutex); } @@ -789,7 +791,7 @@ void cqm_setup_limbo_handler(struct rdt_domain *dom, un= signed long delay_ms) unsigned long delay =3D msecs_to_jiffies(delay_ms); int cpu; =20 - cpu =3D cpumask_any(&dom->cpu_mask); + cpu =3D cpumask_any_housekeeping(&dom->cpu_mask); dom->cqm_work_cpu =3D cpu; =20 schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); @@ -799,10 +801,10 @@ void mbm_handle_overflow(struct work_struct *work) { unsigned long delay =3D msecs_to_jiffies(MBM_OVERFLOW_INTERVAL); struct rdtgroup *prgrp, *crgrp; - int cpu =3D smp_processor_id(); struct list_head *head; struct rdt_resource *r; struct rdt_domain *d; + int cpu; =20 mutex_lock(&rdtgroup_mutex); =20 @@ -823,6 +825,11 @@ void mbm_handle_overflow(struct work_struct *work) update_mba_bw(prgrp, d); } =20 + /* + * Re-check for housekeeping CPUs. This allows the overflow handler to + * move off a nohz_full CPU quickly. + */ + cpu =3D cpumask_any_housekeeping(&d->cpu_mask); schedule_delayed_work_on(cpu, &d->mbm_over, delay); =20 out_unlock: @@ -836,7 +843,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom,= unsigned long delay_ms) =20 if (!static_branch_likely(&rdt_mon_enable_key)) return; - cpu =3D cpumask_any(&dom->cpu_mask); + cpu =3D cpumask_any_housekeeping(&dom->cpu_mask); dom->mbm_work_cpu =3D cpu; schedule_delayed_work_on(cpu, &dom->mbm_over, delay); } --=20 2.39.2