Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5dab0967-8236-534c-a2c4-13cda9cc7150@intel.com>
Date:   Thu, 15 Jun 2023 15:10:09 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Firefox/102.0 Thunderbird/102.11.2
Subject: Re: [PATCH v4 11/24] x86/resctrl: Add cpumask_any_housekeeping() for
 limbo/overflow
Content-Language: en-US
To:     James Morse <james.morse@arm.com>, <x86@kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     Fenghua Yu <fenghua.yu@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        Babu Moger <Babu.Moger@amd.com>,
        <shameerali.kolothum.thodi@huawei.com>,
        D Scott Phillips OS <scott@os.amperecomputing.com>,
        <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 <quic_jiles@quicinc.com>,
        Xin Hao <xhao@linux.alibaba.com>, <peternewman@google.com>,
        <dfustini@baylibre.com>
References: <20230525180209.19497-1-james.morse@arm.com>
 <20230525180209.19497-12-james.morse@arm.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <20230525180209.19497-12-james.morse@arm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?RHMzM3RCdU1OZUhVQmxEaHRvVlc4NDl4b0FPRk93eEZHNTU1bm96WXIzV0ZJ?=
 =?utf-8?B?dGlRMEdFVGg2clcrMG9iNkZSSndMSlBLL0ZSTlNGTVNnMHN3anhtN3g4R2xM?=
 =?utf-8?B?cTdpQjJFMjVvd0NJRFIrRmJ2QjM1S2tLemE1WXVHNlBOYW9zU1V3ODdxYXk5?=
 =?utf-8?B?UnRkNWpUTGdvZ0pYTVRUOFIwUkV3L0xrSzVHZk5MMzhBUVFQeXlVbzlnajBu?=
 =?utf-8?B?NnMxR3FicjRFdlFrbTlKUEczVTFoS3RWZVU2eTlyMkVkbjM2TSs1dy9VUElo?=
 =?utf-8?B?QUdaUVR0VnpwdTNHNDV3WThZWnNMSlQ0T1p2K1IyYklXL2JiRGJMd2Q2OE1K?=
 =?utf-8?B?YVYwTnhYZHdYOG1GNFhIelRaNE9wbkg3dW5mSGFqQy93ZmlqOFRKcnhBdU93?=
 =?utf-8?B?V1JYRjVLck9NNzNIQUd1MVIwZmRvUXVJeXdiY1JTWnpLb1c2S3MwZUJvNFNO?=
 =?utf-8?B?TGg4K0dXQmpGUGk0YUpoUjZucStNRGVGZFhzNWFLU202S3RLL29SZVBOMHFJ?=
 =?utf-8?B?YXYxQ3ZZRTl2aHJSV1plYmpMb2MvT0ZIckRYNUhZWWo5anE4OVNqT1AxT0xP?=
 =?utf-8?B?d1RHTGhsbFpuNnhpWk9rWmE2bHh5a0pqaWlPbUhONmxIRExuZ3YwUXlNZjZW?=
 =?utf-8?B?azU3UXJHTUpvaHBQWFRLTlpSbGpkRjNaWlNWLy9TMlhySGl2SzQ0eUxVQWNI?=
 =?utf-8?B?ZWlVOEpOS1FiTGlBelN2T0U3d3FKYXpna1lTZjMxbmtZYWNTZDB3SHUzQzZG?=
 =?utf-8?B?Y3JGdmlsUWFxaWRlMll6dmdzTXJPNVBaZGplN3prZXVHSXljQ3hsZWVFWUNz?=
 =?utf-8?B?OW1WSkZlZi9wUWp3UlRWL1hmemVzcXhYeUwvRWgxdWdWOUdzRks0S2wyQ1Nl?=
 =?utf-8?B?cWE5bDNCN2xXR1JqRUs0akxMcVBtRVhqRm1OKzFGbGhnMUJ3Z3hEdmc5OWhz?=
 =?utf-8?B?TlFhU3pWZUJ1Y2tFZDA1bFFPRnNjS3NJL3EwK1QvUlhCMlYyeTlBUG40cnNp?=
 =?utf-8?B?cWtkenZBellkUGlUUTJySW5hRWxQMi9xc2ZGTFZNeGc4M3VSdHZieHQ4TzR1?=
 =?utf-8?B?VU5mblMvTFJXcUZYM0twM2VUc0ZOV1d3M0xvZnVFNkROSEhEb280UGJvcmtQ?=
 =?utf-8?B?NG81eWVqVHFsYTkvYjJKVHdCVVVlUXRvWFJRUHdtSDNGZVB2K2g3L2djUWY0?=
 =?utf-8?B?am85bFU0V1pUcUJLVDZKUWFIRjUvcW5PUlROT1kzc2huZkNtdjdya01GZkZH?=
 =?utf-8?B?ZnlEYjRSSnJkVi95RFhVdWg3TmdWay91c1crVXdvMU51MEN3MWZ0YXlJRFhn?=
 =?utf-8?B?RGo1S3hSa0FOTXJZUkFvRE9oc0NFNkRVZkRhTjJwYkwybGllc2RjaFYxS2ty?=
 =?utf-8?B?emlmTTdha3VxQytoa3g3ZVdML1hnVVNKR0F0cmNMMXpXb3hzZ0xoWlBwRVBQ?=
 =?utf-8?B?ZEtSS3dZbW1tdWdBbDY3OFdlZWVBN0c4aFpCcTBqZWkxL1p2VjVFL3pkUC9i?=
 =?utf-8?B?ZFhISGpGeHNQZkxtTjY5dVp1MlEwRWFCanBnZ09hNzUvandEQnFSK24xSFNm?=
 =?utf-8?B?dDdQaXRGS3lDTDhYbkhvMWVzYk8wMm5pekVYYWUzSW9FSnpId3hxSS9MT0FL?=
 =?utf-8?B?ZTBGRC9qcUdIM2JIT2lxQ3FGYVFWalJ1dC9yQWxQQjlnOEZIY0VUMW1nQjgw?=
 =?utf-8?B?dWZyZG5seWhDd0NsVkgxVXNKRFcxQ2c2Uk1jY2lSbXF2Z2JncmVWZ1pKMS9n?=
 =?utf-8?B?djdvd0dYRFQ0Y2JITWcxdzZ1VENFZXB3NWE3VmtNWVRkM2I0bXJPcFdTU0tY?=
 =?utf-8?B?QmRnUVdoRlpON2tSajFNUTBrV0xOUkpTRjYwaDQxZ2ZrQnlpVFJMZHhBUk1h?=
 =?utf-8?B?NzRpaEM0Y3N3anMzSVFxcjdOQVZpaG1vZVBBWjJTZ3lsSjA2MjN1N1FNY05Y?=
 =?utf-8?B?Y2xBZndUbitvNkNqbmp5b3l2eXdrUFpoYVBGbjd4TWs0ZVdYYnBzc3ZhUnFm?=
 =?utf-8?B?YTdsQlhPa1JTQ1VwT3VpS0NnemtTL2VTYU15MGdiUExLbTVUZCtxWnB2REIz?=
 =?utf-8?B?dUJnb2E3ZnVHZmxHVFZNV2pYUE1oanZYU05aUWtlRkdzd2YvN1JIUnBFRlRI?=
 =?utf-8?B?NlZzdVp1OC9QK0dKWmtwUlhIcjRiSTRqSmZQRGNkdmJXTkFYWTVsRG13Q2o0?=
 =?utf-8?B?d1E9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 28177382-66db-42b4-19bd-08db6ded4961
X-MS-Exchange-CrossTenant-AuthSource: SJ2PR11MB7573.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jun 2023 22:10:11.0563
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 1LpZ7DKpM0G15bumZ0SMOthu+PjZDrjaGSqrDHrJpqxftk5ppeJht0Hqzh6E6+x5z8ZwjbEr+Arv7hdT2yuKsqWaA/WtHQlSUQyXCiehiLQ=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR11MB8204
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE
        autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi James,

On 5/25/2023 11:01 AM, James Morse wrote:

...

> @@ -55,6 +56,28 @@
>  /* 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)
> +{
> +	int cpu, hk_cpu;

Should both of these be unsigned int?

> +
> +	cpu = cpumask_any(mask);
> +	if (tick_nohz_full_cpu(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 128d4c7206e4..e267869d60d5 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -770,9 +770,9 @@ 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_resource *r;
>  	struct rdt_domain *d;
> +	int cpu;
>  
>  	mutex_lock(&rdtgroup_mutex);
>  
> @@ -781,8 +781,10 @@ void cqm_handle_limbo(struct work_struct *work)
>  
>  	__check_limbo(d, false);
>  
> -	if (has_busy_rmid(r, d))
> +	if (has_busy_rmid(r, d)) {
> +		cpu = cpumask_any_housekeeping(&d->cpu_mask);
>  		schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);

I expected cqm_work_cpu to also change when the worker moves to a different CPU.

> +	}
>  
>  	mutex_unlock(&rdtgroup_mutex);
>  }
> @@ -792,7 +794,7 @@ 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);
> @@ -802,10 +804,10 @@ 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;
> +	int cpu;
>  
>  	mutex_lock(&rdtgroup_mutex);
>  
> @@ -826,6 +828,11 @@ void mbm_handle_overflow(struct work_struct *work)
>  			update_mba_bw(prgrp, d);
>  	}
>  
> +	/*
> +	 * Re-check for housekeeping CPUs. This allows the overflow handler to
> +	 * move off a nohz_full CPU quickly.
> +	 */
> +	cpu = cpumask_any_housekeeping(&d->cpu_mask);
>  	schedule_delayed_work_on(cpu, &d->mbm_over, delay);

Here I expected mbm_work_cpu to change if the worker moves to a different CPU. 

>  
>  out_unlock:
> @@ -839,7 +846,7 @@ 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);
>  }

Reinette