linux-kernel - Re: [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts delivery to guests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 10 Sep 2012 20:36:48 +0900
From:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
To:	jan.kiszka@...mens.com
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [RFC v2 PATCH 00/21] KVM: x86: CPU isolation and direct interrupts
 delivery to guests

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@...achi.com>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/