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Date:   Wed, 9 Feb 2022 16:47:28 +0530
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Subject: Re: [PATCH] sched/fair: Consider cpu affinity when allowing NUMA
 imbalance in find_idlest_group
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To:     Peter Zijlstra <peterz@infradead.org>
Cc:     aubrey.li@linux.intel.com, efault@gmx.de, gautham.shenoy@amd.com,
        linux-kernel@vger.kernel.org, mgorman@techsingularity.net,
        mingo@kernel.org, song.bao.hua@hisilicon.com,
        srikar@linux.vnet.ibm.com, valentin.schneider@arm.com,
        vincent.guittot@linaro.org
References: <20220207155921.21321-1-kprateek.nayak@amd.com>
 <20220209104625.GM23216@worktop.programming.kicks-ass.net>
From:   K Prateek Nayak <kprateek.nayak@amd.com>
In-Reply-To: <20220209104625.GM23216@worktop.programming.kicks-ass.net>
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Hello Peter,

On 2/9/2022 4:16 PM, Peter Zijlstra wrote:
> On Mon, Feb 07, 2022 at 09:29:21PM +0530, K Prateek Nayak wrote:
>> Neither the sched/tip nor Mel's v5 patchset [1] provides an optimal
>> new-task wakeup strategy when the tasks are affined to a subset of cpus
>> which can result in piling of tasks on the same set of CPU in a NUMA
>> group despite there being other cpus in a different NUMA group where the
>> task could have run in. 
> Where does this affinity come from?

The affinity comes from limiting the process to run on certain subset
of available cpus by modifying the cpus_ptr member of task_struck
of process via taskset or numactl.

---
Thanks and Regards
Prateek