linux-kernel - RE: [PATCH v6 5/5] KVM: selftests: Allowing running dirty_log_perf

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Message-ID: <DS0PR11MB63735722DBD08190B849DD9DDC329@DS0PR11MB6373.namprd11.prod.outlook.com>
Date:   Fri, 28 Oct 2022 02:11:11 +0000
From:   "Wang, Wei W" <wei.w.wang@...el.com>
To:     Vipin Sharma <vipinsh@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "andrew.jones@...ux.dev" <andrew.jones@...ux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v6 5/5] KVM: selftests: Allowing running
 dirty_log_perf_test on specific CPUs

On Friday, October 28, 2022 4:03 AM, Vipin Sharma wrote:
> pthread_create() will internally call sched_setaffinity() syscall after creation of a
> thread on a random CPU. So, from the performance side there is not much
> difference between the two approaches.

The main difference I see is that the vcpu could be created on one NUMA node by
default initially and then gets pinned to another NUMA node.

> 
> However, we will still need pin_this_task_to_pcpu()/sched_affinity()
> to move the main thread to a specific pCPU, therefore, I am thinking of keeping
> the current approach unless there is a strong objection to it.

I also don’t have strong objections, and it's up to you for now.
I will re-visit this later after the code consolidation patchset is landed
and see how this could be better consolidated from all user's perspective.