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

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Date:   Fri, 28 Oct 2022 10:37:04 -0700
From:   Vipin Sharma <vipinsh@...gle.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>
Cc:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "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 Thu, Oct 27, 2022 at 7:11 PM Wang, Wei W <wei.w.wang@...el.com> wrote:
>
> 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.
>

pthread_create(..., &attr,...) calls clone and then
sched_setaffinity(). This is not different than calling
pthread_create(...,NULL,...) and then explicitly calling
sched_setaffinity() by a user. vCPU creation on one NUMA node and then
getting pinned to another NUMA node is equally probable in both
approaches.