From: Avi Kivity <avi@redhat.com>
To: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, yrl.pp-manager.tt@hitachi.com
Subject: Re: [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests
Date: Thu, 06 Sep 2012 14:46:28 +0300 [thread overview]
Message-ID: <50488D14.4010304@redhat.com> (raw)
In-Reply-To: <20120906112718.13320.8231.stgit@kvmdev>
On 09/06/2012 02:27 PM, Tomoki Sekiyama wrote:
> This RFC patch series provides facility to dedicate CPUs to KVM guests
> and enable the guests to handle interrupts from passed-through PCI devices
> directly (without VM exit and relay by the host).
>
> With this feature, we can improve throughput and response time of the device
> and the host's CPU usage by reducing the overhead of interrupt handling.
> This is good for the application using very high throughput/frequent
> interrupt device (e.g. 10GbE NIC).
> Real-time applicatoins also gets benefit from CPU isolation feature, which
> reduces interfare from host kernel tasks and scheduling delay.
>
> The overview of this patch series is presented in CloudOpen 2012.
> The slides are available at:
> http://events.linuxfoundation.org/images/stories/pdf/lcna_co2012_sekiyama.pdf
During Plumbers 2012, both Intel and AMD disclosed upcoming features to
their processors (APIC-V and AVIC) that allow directing device
interrupts to guest vcpus without host kernel involvement. This works
without pinning, dedicating a core to a guest, or any special measures
beyond support for the feature.
CPU isolation is still useful to improve real-time latency further, but
this is really independent of kvm.
I am inclined to reject this feature in favour of the new hardware
support. Sorry, I know this isn't nice to hear, but the extra
maintenance burden cannot be justified for a niche use case with special
limitations when generally useful feature exploiting proper hardware
support provides the same functionality.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-09-06 11:46 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-06 11:27 [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 01/21] x86: Split memory hotplug function from cpu_up() as cpu_memory_up() Tomoki Sekiyama
2012-09-06 11:31 ` Avi Kivity
2012-09-06 11:32 ` Avi Kivity
2012-09-06 11:27 ` [RFC v2 PATCH 02/21] x86: Add a facility to use offlined CPUs as slave CPUs Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 03/21] x86: Support hrtimer on " Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 04/21] x86: Avoid RCU warnings " Tomoki Sekiyama
2012-09-20 17:34 ` Paul E. McKenney
2012-09-28 8:10 ` Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 05/21] KVM: Enable/Disable virtualization on slave CPUs are activated/dying Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 06/21] KVM: Add facility to run guests on slave CPUs Tomoki Sekiyama
2012-09-06 11:27 ` [RFC v2 PATCH 07/21] KVM: handle page faults of slave guests on online CPUs Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 08/21] KVM: Add KVM_GET_SLAVE_CPU and KVM_SET_SLAVE_CPU to vCPU ioctl Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 09/21] KVM: Go back to online CPU on VM exit by external interrupt Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 10/21] KVM: proxy slab operations for slave CPUs on online CPUs Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 11/21] KVM: no exiting from guest when slave CPU halted Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 12/21] x86/apic: Enable external interrupt routing to slave CPUs Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 13/21] x86/apic: IRQ vector remapping on slave for " Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 14/21] KVM: Directly handle interrupts by guests without VM EXIT on " Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 15/21] KVM: add tracepoint on enabling/disabling direct interrupt delivery Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 16/21] KVM: vmx: Add definitions PIN_BASED_PREEMPTION_TIMER Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 17/21] KVM: add kvm_arch_vcpu_prevent_run to prevent VM ENTER when NMI is received Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 18/21] KVM: route assigned devices' MSI/MSI-X directly to guests on slave CPUs Tomoki Sekiyama
2012-09-06 11:28 ` [RFC v2 PATCH 19/21] KVM: Enable direct EOI for directly routed interrupts to guests Tomoki Sekiyama
2012-09-06 11:29 ` [RFC v2 PATCH 20/21] KVM: Pass-through local APIC timer of on slave CPUs to guest VM Tomoki Sekiyama
2012-09-06 11:29 ` [RFC v2 PATCH 21/21] x86: request TLB flush to slave CPU using NMI Tomoki Sekiyama
2012-09-06 11:46 ` Avi Kivity [this message]
2012-09-07 8:26 ` [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests Jan Kiszka
2012-09-10 11:36 ` Tomoki Sekiyama
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