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[2604:1380:45e3:2400::1]) by mx.google.com with ESMTPS id z8-20020a17090a66c800b0028ac62816d2si368198pjl.1.2023.12.15.09.47.18 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Dec 2023 09:47:18 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-1451-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel+bounces-1451-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-1451-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id 7B12E28A441 for ; Fri, 15 Dec 2023 17:47:18 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C2D613012A; Fri, 15 Dec 2023 17:44:43 +0000 (UTC) X-Original-To: linux-kernel@vger.kernel.org Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C8C21563AE for ; Fri, 15 Dec 2023 17:44:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 60DD91650; Fri, 15 Dec 2023 09:45:24 -0800 (PST) Received: from merodach.members.linode.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6AE663F5A1; Fri, 15 Dec 2023 09:44:36 -0800 (PST) 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, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, Babu Moger Subject: [PATCH v8 12/24] x86/resctrl: Add cpumask_any_housekeeping() for limbo/overflow Date: Fri, 15 Dec 2023 17:43:31 +0000 Message-Id: <20231215174343.13872-13-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20231215174343.13872-1-james.morse@arm.com> References: <20231215174343.13872-1-james.morse@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1785370969071271538 X-GMAIL-MSGID: 1785370969071271538 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 Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Babu Moger Reviewed-by: Shaopeng Tan Reviewed-by: Reinette Chatre Reviewed-by: Babu Moger --- Changes since v3: * typos fixed Changes since v4: * Made temporary variables unsigned Changes since v5: * Restructured cpumask_any_housekeeping() to avoid later churn. Changes since v6: * Update mbm_work_cpu/cqm_work_cpu when rescheduling. --- arch/x86/kernel/cpu/resctrl/internal.h | 24 ++++++++++++++++++++++++ arch/x86/kernel/cpu/resctrl/monitor.c | 20 +++++++++++++------- 2 files changed, 37 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h index 521afa016b05..33e24fcc8dd0 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 @@ -56,6 +57,29 @@ /* Max event bits supported */ #define MAX_EVT_CONFIG_BITS GENMASK(6, 0) +/** + * 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 = cpumask_any(mask); + if (!tick_nohz_full_cpu(cpu)) + return cpu; + + hk_cpu = cpumask_nth_andnot(0, mask, tick_nohz_full_mask); + if (hk_cpu < nr_cpu_ids) + cpu = 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/resctrl/monitor.c index fdbef88ff39b..8737a9d6caef 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -783,7 +783,6 @@ static void mbm_update(struct rdt_resource *r, struct rdt_domain *d, void cqm_handle_limbo(struct work_struct *work) { unsigned long delay = msecs_to_jiffies(CQM_LIMBOCHECK_INTERVAL); - int cpu = smp_processor_id(); struct rdt_domain *d; mutex_lock(&rdtgroup_mutex); @@ -792,8 +791,11 @@ void cqm_handle_limbo(struct work_struct *work) __check_limbo(d, false); - if (has_busy_rmid(d)) - schedule_delayed_work_on(cpu, &d->cqm_limbo, delay); + if (has_busy_rmid(d)) { + d->cqm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask); + schedule_delayed_work_on(d->cqm_work_cpu, &d->cqm_limbo, + delay); + } mutex_unlock(&rdtgroup_mutex); } @@ -803,7 +805,7 @@ void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms) unsigned long delay = msecs_to_jiffies(delay_ms); int cpu; - cpu = cpumask_any(&dom->cpu_mask); + cpu = cpumask_any_housekeeping(&dom->cpu_mask); dom->cqm_work_cpu = cpu; schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); @@ -813,7 +815,6 @@ void mbm_handle_overflow(struct work_struct *work) { unsigned long delay = msecs_to_jiffies(MBM_OVERFLOW_INTERVAL); struct rdtgroup *prgrp, *crgrp; - int cpu = smp_processor_id(); struct list_head *head; struct rdt_resource *r; struct rdt_domain *d; @@ -837,7 +838,12 @@ void mbm_handle_overflow(struct work_struct *work) update_mba_bw(prgrp, d); } - schedule_delayed_work_on(cpu, &d->mbm_over, delay); + /* + * Re-check for housekeeping CPUs. This allows the overflow handler to + * move off a nohz_full CPU quickly. + */ + d->mbm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask); + schedule_delayed_work_on(d->mbm_work_cpu, &d->mbm_over, delay); out_unlock: mutex_unlock(&rdtgroup_mutex); @@ -850,7 +856,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms) if (!static_branch_likely(&rdt_mon_enable_key)) return; - cpu = cpumask_any(&dom->cpu_mask); + cpu = cpumask_any_housekeeping(&dom->cpu_mask); dom->mbm_work_cpu = cpu; schedule_delayed_work_on(cpu, &dom->mbm_over, delay); }