From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: David Matlack <dmatlack@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Suleiman Souhlal <suleiman@google.com>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: Re: [PATCHV2 1/3] KVM: x86: introduce kvm_mmu_pte_prefetch structure
Date: Thu, 21 Oct 2021 17:09:29 +0900 [thread overview]
Message-ID: <YXEgOf1JzTmdRP6u@google.com> (raw)
In-Reply-To: <YXDeRej39voc7lJU@google.com>
On (21/10/21 12:28), Sergey Senozhatsky wrote:
> >
> > We are using TDP. And somehow I never see (literally never) async PFs.
> > It's always either hva_to_pfn_fast() or hva_to_pfn_slow() or
> > __direct_map() from tdp_page_fault().
>
> Hmm, and tdp_page_fault()->fast_page_fault() always fails on
> !is_access_allowed(error_code, new_spte), it never handles the faults.
> And I see some ->mmu_lock contention:
>
> spin_lock(&vcpu->kvm->mmu_lock);
> __direct_map();
> spin_unlock(&vcpu->kvm->mmu_lock);
>
> So it might be that we setup guest memory wrongly and never get
> advantages of TPD and fast page faults?
No, never mind, that's probably expected and ->mmu_lock contention is not
severe.
next prev parent reply other threads:[~2021-10-21 8:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 15:32 [PATCHV2 0/3] kvm: x86: make PTE_PREFETCH_NUM tunable Sergey Senozhatsky
2021-10-19 15:32 ` [PATCHV2 1/3] KVM: x86: introduce kvm_mmu_pte_prefetch structure Sergey Senozhatsky
2021-10-19 22:44 ` David Matlack
2021-10-20 1:23 ` Sergey Senozhatsky
2021-10-20 15:56 ` David Matlack
2021-10-21 2:48 ` Sergey Senozhatsky
2021-10-21 3:28 ` Sergey Senozhatsky
2021-10-21 8:09 ` Sergey Senozhatsky [this message]
2021-10-19 15:32 ` [PATCHV2 2/3] KVM: x86: use mmu_pte_prefetch for guest_walker Sergey Senozhatsky
2021-10-19 15:32 ` [PATCHV2 3/3] KVM: x86: add KVM_SET_MMU_PREFETCH ioctl Sergey Senozhatsky
2021-10-19 15:38 ` Sergey Senozhatsky
2021-11-08 21:47 ` Sean Christopherson
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