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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CO1PEPF000044F6.mail.protection.outlook.com (10.167.241.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8314.0 via Frontend Transport; Fri, 27 Dec 2024 04:40:57 +0000 Received: from [10.252.205.52] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Thu, 26 Dec 2024 22:40:52 -0600 Message-ID: Date: Fri, 27 Dec 2024 10:10:49 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] sched/fair: Ensure select housekeeping cpus in task_numa_find_cpu To: Chuyi Zhou , , , , , , , , , CC: , References: <20241216122357.1276382-1-zhouchuyi@bytedance.com> <20241216122357.1276382-4-zhouchuyi@bytedance.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Dec 2024 04:40:57.7235 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1387b799-f95b-4f5e-32b2-08dd2630a837 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000044F6.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8085 Hello Chuyi, On 12/23/2024 6:28 PM, Chuyi Zhou wrote: > > > 在 2024/12/18 14:21, K Prateek Nayak 写道: >> Hello Chuyi, >> >> On 12/16/2024 5:53 PM, Chuyi Zhou wrote: >>> [..snip..] >>> @@ -2081,6 +2081,12 @@ numa_type numa_classify(unsigned int imbalance_pct, >>>       return node_fully_busy; >>>   } >>> +static inline bool numa_migrate_test_cpu(struct task_struct *p, int cpu) >>> +{ >>> +    return cpumask_test_cpu(cpu, p->cpus_ptr) && >>> +            housekeeping_cpu(cpu, HK_TYPE_DOMAIN); >>> +} >>> + >>>   #ifdef CONFIG_SCHED_SMT >>>   /* Forward declarations of select_idle_sibling helpers */ >>>   static inline bool test_idle_cores(int cpu); >>> @@ -2168,7 +2174,7 @@ static void task_numa_assign(struct task_numa_env *env, >>>           /* Find alternative idle CPU. */ >>>           for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) { >> >> Can we just do: >> >>      for_each_cpu_and(cpu, cpumask_of_node(env->dst_nid), housekeeping_cpumask(HK_TYPE_DOMAIN)) { >>          ... >>      } >> >> and avoid adding numa_migrate_test_cpu(). Thoughts? > > Make sense, but now there doesn't seem to be an API like for_each_cpu_wrap_and(). > > Do you think the following is better? > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 855df103f4dd..4792ef672738 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2167,9 +2167,9 @@ static void task_numa_assign(struct task_numa_env *env, >                 int start = env->dst_cpu; > >                 /* Find alternative idle CPU. */ > -               for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) { > +               for_each_cpu_and(cpu, cpumask_of_node(env->dst_nid), housekeeping_cpumask(HK_TYPE_DOMAIN)) { >                         if (cpu == env->best_cpu || !idle_cpu(cpu) || "start" is set to "env->dst_cpu" is already taken care here with the first comparison. > -                           !cpumask_test_cpu(cpu, env->p->cpus_ptr)) { > +                               cpu == start || !cpumask_test_cpu(cpu, env->p->cpus_ptr)) { >                                 continue; >                         } > I think the for_each_cpu_wrap() was used to reduce contention for xchg operation below. Perhaps we can have a per-cpu temporary mask (like load_balance_mask) if we want to reduce the xchg contention and break this into cpumask_and() + for_each_cpu_wrap() steps. I'm not sure if any of the existing masks (load_balance_mask, select_rq_mask, should_we_balance_tmpmask) can be safely reused. Otherwise, perhaps we can make a case for for_each_cpu_and_wrap() with this use case. > > Thanks. > > >> >>>               if (cpu == env->best_cpu || !idle_cpu(cpu) || >>> -                !cpumask_test_cpu(cpu, env->p->cpus_ptr)) { >>> +                !numa_migrate_test_cpu(env->p, cpu)) { >>>                   continue; >>>               } >>> @@ -2480,7 +2486,7 @@ static void task_numa_find_cpu(struct task_numa_env *env, >>>       for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { >> >> Same modifications can be made for this outer loop. >> > -- Thanks and Regards, Prateek