From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpeng.li@hotmail.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v2] KVM: VMX: Cache IA32_DEBUGCTL in memory
Date: Tue, 5 Dec 2017 22:54:51 +0100 [thread overview]
Message-ID: <20171205215450.GD17273@flask> (raw)
In-Reply-To: <1511947880-21643-1-git-send-email-wanpeng.li@hotmail.com>
2017-11-29 01:31-0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT, so it is saved/restored
> each time during world switch. Jim from Google pointed out that
> when running schbench in L2, vmx_vcpu_run will occupy 4% cpu time,
> and the 25% of vmx_vcpu_run cpu time is occupied by get_debugctlmsr().
> This patch caches the host IA32_DEBUGCTL MSR and saves/restores
> the host IA32_DEBUGCTL msr when guest/host switches to avoid to
> save/restore each time during world switch.
>
> Suggested-by: Jim Mattson <jmattson@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Jim Mattson <jmattson@google.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
Queued, thanks.
And there is another optimization loosely connected to the "[PATCH v3
00/16] Move vcpu_load and vcpu_put calls to arch code" series:
We only need to read the value for the KVM_RUN ioctl.
next prev parent reply other threads:[~2017-12-05 21:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 9:31 [PATCH v2] KVM: VMX: Cache IA32_DEBUGCTL in memory Wanpeng Li
2017-11-29 16:55 ` Jim Mattson
2017-11-29 17:32 ` David Hildenbrand
2017-12-05 21:54 ` Radim Krčmář [this message]
2017-12-06 0:15 ` Nadav Amit
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