From: Paolo Bonzini <pbonzini@redhat.com>
To: David Hildenbrand <david@redhat.com>,
"Maciej S. Szmigiero" <mail@maciej.szmigiero.name>,
Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Igor Mammedov <imammedo@redhat.com>,
Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Huacai Chen <chenhuacai@kernel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Paul Mackerras <paulus@ozlabs.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Cornelia Huck <cohuck@redhat.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: Scalable memslots implementation
Date: Wed, 3 Feb 2021 15:33:38 +0100 [thread overview]
Message-ID: <d6e3d6b2-e6fd-c0ae-db17-2218770ce4ed@redhat.com> (raw)
In-Reply-To: <b9aacf06-de2b-b831-6210-25191dd1b0ac@redhat.com>
On 03/02/21 14:52, David Hildenbrand wrote:
>>
>> However, note that the TDP MMU does not need an rmap at all. Since that
>> one is getting ready to become the default, the benefits of working on
>> the rmap would be quite small and only affect nested virtualization.
>
> Right, but we currently always have to allocate it.
>
> 8 bytes per 4k page, 8 bytes per 2M page, 8 bytes per 1G page.
>
> The 4k part alone is 0.2% of the memblock size.
>
> For a 1 TB memslot we might "waste" > 2 GB on rmap arrays.
>
> (that's why I am asking :) )
Yes, we're in violent agreement. :) I mean that the simplest solution
would be to allocate it lazily when building a non-TDP root.
Paolo
next prev parent reply other threads:[~2021-02-03 14:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 8:13 [PATCH 1/2] KVM: x86/mmu: Make HVA handler retpoline-friendly Maciej S. Szmigiero
2021-02-01 8:13 ` [PATCH 2/2] KVM: Scalable memslots implementation Maciej S. Szmigiero
2021-02-02 1:33 ` Sean Christopherson
2021-02-02 22:42 ` Maciej S. Szmigiero
2021-02-02 23:43 ` Sean Christopherson
2021-02-03 10:44 ` Maciej S. Szmigiero
2021-02-03 14:21 ` Vitaly Kuznetsov
2021-02-03 20:10 ` Maciej S. Szmigiero
2021-02-03 13:43 ` Paolo Bonzini
2021-02-03 13:41 ` Paolo Bonzini
2021-02-03 13:44 ` David Hildenbrand
2021-02-03 13:46 ` Paolo Bonzini
2021-02-03 13:52 ` David Hildenbrand
2021-02-03 14:33 ` Paolo Bonzini [this message]
2021-02-03 20:09 ` Maciej S. Szmigiero
2021-02-01 8:21 ` [PATCH 1/2] KVM: x86/mmu: Make HVA handler retpoline-friendly Paolo Bonzini
2021-02-01 15:19 ` Maciej S. Szmigiero
2021-02-03 14:43 ` Paolo Bonzini
2021-02-03 20:09 ` Maciej S. Szmigiero
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