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From: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
To: jan.kiszka@siemens.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests
Date: Mon, 10 Sep 2012 20:36:48 +0900	[thread overview]
Message-ID: <504DD0D0.1040400@hitachi.com> (raw)
In-Reply-To: <5049AFD0.1060700@siemens.com>

Hi Jan,

On 2012/09/07 17:26, Jan Kiszka wrote:

> On 2012-09-06 13:27, 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
> 
> One question regarding your benchmarks: If you measured against standard
> KVM, were the vCPU thread running on an isolcpus core of its own as
> well? If not, your numbers about the impact of these patches on maximum,
> maybe also average latencies are likely too good. Also, using a non-RT
> host and possibly a non-prioritized vCPU thread for the standard
> scenario looks like an unfair comparison.


In the standard KVM benchmark, the vCPU thread is pinned down to its own
CPU core. In addition, the vCPU thread and irq/*-kvm threads are both set
to the max priority with SCHED_RR policy.

As you said, RT-host may result in better max latencies as below.
(But min/average latencies became worse, however, this might be our setup
 issue.)
                                 Min / Avg / Max latencies
Normal KVM
  RT-host     (3.4.4-rt14)      15us / 21us / 117us
  non RT-host (3.5.0-rc6)        6us / 11us / 152us
KVM + Direct IRQ
  non RT-host (3.5.0-rc6 +patch) 1us /  2us /  14us

Thanks,
-- 
Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory


      reply	other threads:[~2012-09-10 11:38 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 ` [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests Avi Kivity
2012-09-07  8:26 ` Jan Kiszka
2012-09-10 11:36   ` Tomoki Sekiyama [this message]

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