linux-kernel - Re: [PATCH v4 3/3] KVM: x86/mmu: Add detailed page size stats

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Date:   Mon, 9 Aug 2021 16:39:38 -0700
From:   Mingwei Zhang <mizhang@...gle.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v4 3/3] KVM: x86/mmu: Add detailed page size stats

Hi Jim,

No, I don't think 512G is supported. So, I will remove the
'pages_512G' metric in my next version.

Thanks.
-Mingwei

On Mon, Aug 9, 2021 at 3:26 PM Jim Mattson <jmattson@...gle.com> wrote:
>
> On Mon, Aug 2, 2021 at 9:46 PM Mingwei Zhang <mizhang@...gle.com> wrote:
> >
> > Existing KVM code tracks the number of large pages regardless of their
> > sizes. Therefore, when large page of 1GB (or larger) is adopted, the
> > information becomes less useful because lpages counts a mix of 1G and 2M
> > pages.
> >
> > So remove the lpages since it is easy for user space to aggregate the info.
> > Instead, provide a comprehensive page stats of all sizes from 4K to 512G.
>
> There is no such thing as a 512GiB page, is there? If this is an
> attempt at future-proofing, why not go to 256TiB?